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Adrenoleukodystrophy (ALD) is a rare X-linked disease characterized by accumulation of long fatty acid chains in the adrenal glands, brain, plasma and fibroblasts. This causes a degeneration of the myelin sheath that surrounds and protects the function of the nerve cells. Approximately 1 in 100,000 is affected. There are three basic forms of ALD: neonatal, childhood, and adult-onset. The neonatal form affects both males and females. It progresses rapidly and may lead to mental retardation, facial abnormalities, seizures, poor muscle tone, enlarged liver and adrenal dysfunction. The childhood onset is the most common and also the most severe form. Onset of the disease occurs around the ages of 4-10 years old. Symptoms include behavioral problems, poor memory and speech and vision loss, difficulty in swallowing and unsteadiness in gait. Childhood ALD generally results in total disability and possible death within ten years of onset. Childhood ALD primarily affects males.
Adult-onset ALD, also known as Adrenomyeloneuropathy, is milder and progresses much slower than childhood ALD. Symptoms become apparent around the ages of 21-35 years of age. Lower limbs are primarily affected and may become stiff, weak or completely paralyzed. Patients may also experience loss of coordination. Women who are carriers of ALD may show symptoms but they are usually much less pronounced.
There is no cure or treatment to reverse the effects of ALD. Affected individuals undergo physical therapy and counseling and are usually enrolled in special education. Genetic counseling is highly recommended for families with a history of ALD. The form of ALD may be determined through a comprehensive genetic analysis. Those with childhood or adult-onset ALD may take advantage of a new test called Pre-Implantation Genetic Diagnosis (PGD). PGD tests for genetic abnormalities and can determine the sex of an embryo prior to implantation. Through this mechanism, the chances of having an affected child is greatly reduced. Due to complex inheritance patterns of genetic disorders, an experienced genetic counselor can determine whether PGD will be beneficial. PGD can also test for other genetic conditions and is continually being improved to included more genetic diseases.!
Amyotrophic Lateral Sclerosis (ALS), commonly known as Lou Gehrig’s Disease, is a fatal, progressive neurological disorder. It is estimated that 20,000 - 30,000 people are afflicted with ALS in the United States. Men are more at risk for developing ALS than women and onset usually occurs in midlife. ALS is characterized by the progressive deterioration of motor neurons that control voluntary muscle movement. In the absence of sufficient innervation, voluntary muscles start to weaken and eventually atrophy and lead to paralysis. Early symptoms of ALS include weakness of the arms and/or legs and are often limited to a specific region but eventually spread to the rest of the body as the disease progresses. Individuals with ALS experience frequent tripping and stumbling, difficulty walking and climbing stairs, constant fatigue, twitching and cramping of muscles. Eventually, bulbar muscles become affected and they will experience difficulty breathing, speaking and swallowing.
Diagnosis is made through a complete medical history and physical examination and may include an electromyogram (EMG), blood and urine analysis, x-rays and CT scans to eliminate other motor neurological disorders with similar symptoms. There is currently no cure or effective treatment to reverse or slow the progression of ALS. Once diagnosis is made, physicians and caretakers aim to improve or maintain a normal quality of life for as long as possible. Physical therapy and a regular exercise regime are essential in maintaining muscle strength and range of motion. As the disease progresses, other assisted devices such as a feeding tube and wheelchair may eventually be necessary.
The exact cause of ALS is currently not known. Approximately 10% of ALS are of genetic origin, the rest are sporadic. Various factors are suspected to be involved in ALS. An excess of free radicals and/or the neurotransmitter glutamate may be involved, however, whether they are the cause or the effect of the disease and the mechanism by which they are involved is unknown.
Once diagnosed with ALS, it is important to determine whether it is hereditary or not. A thorough genetic analysis may reveal a familial history and a genetic counselor can advise a couple of the chances of having an affected child. Preimplantation Genetic Diagnosis (PGD) may be an option to some. Due to the higher risk males face in developing ALS, PGD could be quite beneficial for it is able to determine the gender of an embryo prior to implantation. This reduces the chances of having an affected child. It is strongly recommended that couples seek the advice of a genetic counselor. Inheritance patterns of diseases are complex and genetic counselors can determine whether PGD will be beneficial. Although the use of PGD is currently limited in the prevention of ALS, further research and investigation into the causes of ALS may reveal a larger role for genetics. This, along with continual improvements in PGD, will hopefully lead to greater utilization of such a technique.
It is a type of dystrophinopathy, which includes a spectrum of muscle diseases in which there is insufficient dystrophin produced in the muscle cells, resulting in instability in the structure of muscle cell membrane. This is caused by mutations in the dystrophin gene, which encodes the protein dystrophin. Becker's muscular dystrophy is related to Duchenne muscular dystrophy in that both result from a mutation in the dystrophin gene, but in Duchenne muscular dystrophy no functional dystrophin is produced making DMD much more severe than BMD. Both Duchenne and Becker's muscular dystrophy have traditionally been called "X-linked" recessive diseases, but in view of modern molecular biology and identification of the dystrophin gene, it might be more appropriate to say they are X-chromosome recessive diseases.
Also known as Cooley’s Anemia, Beta Thalassemia is an autosomal recessive blood disorder and is characterized by the absence or decreased production of the beta component of hemoglobin, the primary carrier of oxygen in the blood. This compromises the ability of hemoglobin to carry oxygen through the body and causes anemia, a primary symptom of Beta Thalassemia. Beta Thalassemia predominantly affects people of Mediterranean, Near and Middle Eastern, and Southeast Asian descent.
Beta Thalassemia is classified into three types. People who are carriers of Beta Thalassemia, identified as Thalassemia Minor or Trait, are generally healthy and may occasionally experience mild cases of anemia. Approximately 2 million people in the United States are carriers. Thalassemia Intermediate is characterized by moderate anemia, hepatosplenomegaly (enlargement of the liver and spleen), growth failure and jaundice. Age of onset is generally around 2-4 years of age. People affected by Thalassemia Intermediate may require blood transfusions. Thalassemia Major, also commonly known as Cooley’s Anemia, is a much more severe form of anemia. Symptoms are apparent within the first year of an infant’s life. An estimated 300,000 people worldwide are affected with Thalassemia Major.
Treatment for Beta Thalassemia generally include red blood cell transfusions every two to three weeks to maintain sufficient levels of hemoglobin. A side effect of this treatment is an overload of iron. To compensate for this, physicians prescribe chelation therapy in conjunction with the transfusions. Chelation therapy involves the infusion of a medication that binds the excess iron and removes it. It is a difficult and painful procedure and compliance with the treatment is a common problem amongst patients with Beta Thalassemia.
Testing for the disease is strongly recommended to patients who have a family history of anemia, specifically if they belong to one of the ethnic groups listed above. A Complete Blood Count (CBC), particularly the Mean Corpuscular Volume (MCV), may indicate whether an individual is anemic and further tests, i.e. hemoglobin electrophoresis, can further determine whether an individual is affected.
A new test now available for couples at risk is Pre-Implantation Genetic Diagnosis (PGD). This tests an embryo, conceived through IVF, for genetic defects, such as the Beta Thalassemia gene. This ensures that only healthy embryos are implanted, thus preventing the disease from being passed on.
Central core disease (CCD) is an inherited neuromuscular disorder characterised by central cores on muscle biopsy and clinical features of a congenital myopathy. Prevalence is unknown but the condition is probably more common than other congenital myopathies. CCD typically presents in infancy with hypotonia and motor developmental delay and is characterized by predominantly proximal weakness pronounced in the hip girdle; orthopaedic complications are common and malignant hyperthermia susceptibility (MHS) is a frequent complication. CCD and MHS are allelic conditions both due to (predominantly dominant) mutations in the skeletal muscle ryanodine receptor (RYR1) gene, encoding the principal skeletal muscle sarcoplasmic reticulum calcium release channel (RyR1). Altered excitability and/or changes in calcium homeostasis within muscle cells due to mutation-induced conformational changes of the RyR protein are considered the main pathogenetic mechanism(s). The diagnosis of CCD is based on the presence of suggestive clinical features and central cores on muscle biopsy; muscle MRI may show a characteristic pattern of selective muscle involvement and aid the diagnosis in cases with equivocal histopathological findings. Mutational analysis of the RYR1 gene may provide genetic confirmation of the diagnosis. Management is mainly supportive and has to anticipate susceptibility to potentially life-threatening reactions to general anaesthesia. Further evaluation of the underlying molecular mechanisms may provide the basis for future rational pharmacological treatment. In the majority of patients, weakness is static or only slowly progressive, with a favourable long-term outcome.
Centronuclear Myopathy is a form of Myopathy.
Cerebellar Ataxia refers to a condition of unsteadiness of gate. Causes of ataxia are varied. It includes, among others, alcoholism, multiple sclerosis, brain tumors, thyroid disease and genetic abnormalities. It may also result from a viral infection or chicken pox during childhood. Various disorders fall under ataxia, including Freidrich’s Ataxia. Cerebellar Ataxia is caused by the degeneration of the cerebellum, the part of the brain that controls coordination and balance. Onset varies greatly from childhood to late adulthood. Childhood onset of Cerebellar Ataxia is more than likely caused by genetic abnormalities. Most of these cases are inherited in an autosomal recessive fashion, however, there have been rare cases where it has been traced to the X chromosome.
Common symptoms of Cerebellar Ataxia include sudden writhing movements of arms and legs and jerky eye movements. The different types of Cerebellar Ataxia are classified according to cause and specific location affected, but their symptoms do not vary greatly. In rare occasions, symptoms may subside on their own within a few months.
Genetic counseling is strongly encouraged in families with an incidence of Cerebellar Ataxia. A thorough genetic and pedigree analysis must be done in order to determine the form of Cerebellar Ataxia the individual has. Preimplantation Genetic Diagnosis (PGD) maybe of benefit to those families with the X-linked form of the disease. PGD tests for genetic abnormalities in an embryo prior to implantation. It can also determine the embryo’s gender. Implanting only the embryos whose gender is not likely to develop the disease will greatly reduce the chance of having an affected child. An experienced genetic counselor should be able to determine whether PGD will be beneficial. PGD is available for a variety of X-linked diseases and other genetic disorders. It is also being continually improved to encompass other genetic abnormalities.
Charcot-Marie-Tooth Disease refers to a hereditary neurological disorder affecting primarily the legs, feet and hands. It is also known as Hereditary Motor-Sensory Neuropathy (HMSN) and Peroneal Muscle Atrophy. Charcot-Marie-Tooth (CMT) Disease is one of the more common hereditary diseases. One in 2,500 people is afflicted with some form of CMT.
CMT is a neurological disorder because it affects the peripheral nerves that supply the lower body. CMT is divided into two general types, Type I and Type II. Different forms of CMT fall under these two types. Type I affects the myelin sheath that surrounds the nerve fiber. Degeneration of the myelin sheath results in slowed conduction of the nerve signals to the muscles. Type II affects the nerve fibers itself. Conduction is generally normal, but abnormalities are evident in the nerve signals. Because of poor innervation, the muscles of the lower limbs start to weaken and waste away and atrophy. Early symptoms of CMT include high arch of the feet and flexed toes. Some varieties of CMT are associated with other disorders. These include CMT with Freidrich Ataxia, with Ptosis, and with Parkinsonism. Onset generally occurs either in childhood or adolescence. Symptoms vary in severity and progressively worsen. There is no cure for CMT, however, various treatments are widely available. They range from physical therapy, leg braces, shoe inserts and surgery to correct any severe abnormalities. Affected individuals are more vulnerable to injury.
At least six genetic defects have been traced to CMT. Generally, CMT is inherited in an autosomal dominant fashion but some forms of CMT have been found to be X-linked. Symptoms of X-linked forms of CMT are generally more pronounced in males than females. Once a patient is diagnosed with CMT, it is crucial to determine the form of CMT the patient has. A thorough genetic and pedigree analysis should be conducted to determine mode of inheritance of that particular form of CMT. A new test is now available to help couples with a family history of X-linked CMT. Pre-Implantation Genetic Diagnosis (PGD) examines an embryo prior to implantation and determines the sex of the baby. The transmission of diseases that are more prevalent in one gender can be greatly reduced through PGD. A thorough genetic analysis by a genetic counselor is needed to determine if PGD will be of benefit to couples.
Thus far, the following forms of CMT have been found to be X-linked,
CMT1A CMTX1
CMT1B CMTX2
CMT2A CMTX3
CMT2B X-linked with Aplasia Cutis Congenita
CMT2B2 CMT combined with Friedrich Ataxia
CMT4A CMT with Ptosis and Parkinsonism
The forms listed above are not exclusively inherited in an X-linked pattern. PGD can only help in reducing the risk of having a child with CMT. However, PGD, is continuously being improved and hopefully, it will someday test for all the forms of CMT and many other genetic diseases.
Chondrodysplasia Punctata is a hereditary disorder that affects infants and young children. It is a skeletel abnormality, characterized by punctate calcification of the cartilage of the epiphyses, larynx and trachea. Symptoms include growth retardation, shortening of limbs, cataracts, dry and scaly skin (Ichthyosis), large skin pores and patches of coarse, dry hair. Patients may also become mildly retarded. Different forms of Chondrodysplasia Punctata exist, the most common of which is inherited as an autosomal recessive trait. Chondrodysplasia Punctata may also be inherited in a dominant and recessive X-linked fashion . X-linked dominant form, also known as Conradi-Hunermann Syndrome, is lethal to males in early gestation. Females affected with this form show similar symptoms as those listed above. The X-linked recessive form of Chondrodysplasia Punctata affects both males and females, although females may have less pronounced symptoms.
Couples with a familial history of Chondrodysplasia Punctata should seek genetic counseling. A thorough genetic and pedigree analysis by an experienced genetic counselor is strongly recommended to determine the form of Chondrodysplasia Punctata that occurs in their family. A new test called Preimplantation Genetic Diagnosis (PGD) may be of benefit to those with an X-linked form of Chondrodysplasia Punctata. PGD tests for genetic abnormalities and determines the gender in an embryo prior to implantation. PGD can help in reducing the chances of having an affected child. PGD is currently available for a number of genetic disorders and X-linked diseases. PGD is continually being improved so hopefully someday, it may test for all forms of Chondrodysplasia Punctata and other genetic diseases.
Congenital Aganglionic Megacolon is more commonly known as Hirschsprung Disease
Conradi-Hunnerman Syndrome is a form of Chondrodysplasia Punctata.
Cystic Fibrosis is one of the most common genetic disorders in the United States. It affects primarily Caucasians of Northern European descent. An estimated 30,000 children are affected and 1 out of 31 Americans are symptom-free carriers.
Cystic Fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene on chromosome 7. It is inherited as an autosomal recessive trait. CF affects primarily exocrine glands, including respiratory, pancreatic, salivary and sweat glands. In the respiratory system, CF affects the mucus-secreting glands, causing it to produce unusually thick secretions that line the air passageways. Excess mucus causes the air passageways to become clogged, making breathing difficult. It also creates an environment conducive to bacterial growth. In the pancreatic system, CF blocks essential digestive enzymes from the pancreas in reaching the bowel, creating improper absorption of fats and nutrients. CF also increases the amount of salt and chloride in sweat.
The onset and severity of symptoms of CF varies. In infants, it is characterized by vomiting, abdominal swelling, blockage of the small intestines, poor growth, and abnormally large and foul smelling stools that contain excess fat and nutrients due to malabsorption. Onset of CF during childhood could result in chronic coughing, sleep disturbances, wheezing, chronic inflammation of airways, and recurrent lung infections. Progression of the disease may result in permanent lung damage, respiratory failure and/or heart failure.
A standard diagnostic test for CF is the sweat test. The sweat test measures the concentration of salt in the sweat of an individual. Very high concentration of salt in the sweat is a good indicator of CF and further genetic tests can be performed to verify the diagnosis.
Treatment for CF includes removal of the excess mucus. Antibiotics are often used to treat lung infections and affected individuals are generally placed on an enriched diet, supplemented with vitamins, to ensure that they are getting the proper amount of nutrients. Gene therapy is also currently being explored as an option for patients.
Due to the high frequency of carriers among Americans, testing is strongly recommended to those with a family history of Cystic Fibrosis. Recently, the American College of Obstetricians and Gynecologists urged Congress to provide for CF testing of everyone who plans to have a child. Affected couples should also consider Pre-Implantation Genetic Diagnosis (PGD). PGD tests an embryo for genetic defects before implantation. PGD ensures couples that their children will not inherit the disease.
Duchenne Muscular Dystrophy (DMD) is an X-linked disorder that is characterized by progressive muscle weakness and other associated complications. It affects approximately one out of 3,500 males, regardless of ethnic or socioeconomic background. Around the age of five years, affected boys begin to stumble and fall more than is normal. They also generally show a change in posture and often walk on their toes. Some boys with DMD may also experience learning difficulties and may be mildly retarded.
Muscle weakness progresses over time and in some cases, wheelchair use is necessary by the age of thirteen. Complications associated with DMD include breathing difficulties, scoliosis (abnormal curvature of the spine), and heart problems. During the end stages of DMD, the entire body weakens, and the disease involves practically every system of the body. Affected individuals generally die by the age of twenty years, mainly due to severe lung problems or heart failure.
Currently, there is no cure for DMD, but treatments are available for the symptoms. Physiotherapy is available to help strengthen the muscle and to alleviate muscle pain. Inhalants, antibiotics and other medications are also available to ease respiratory problems. Steroid treatment of DMD remains controversial, but is an option. Gene therapy, such as myoblast transfer, is being explored as a possible treatment for DMD.
Although the majority of DMD cases are inherited, about one third of cases of DMD are caused by sporadic and random gene mutation. The chance that a woman with an affected son, apparently due to a sporadic gene mutations, will have another affected son or a daughter who is a carrier is increased. Any family with a history of DMD is strongly encouraged to seek genetic counseling.
Couples now have the option to take advantage of a new test called Pre-Implantation Genetic Diagnosis (PGD). PGD tests for genetic defects, such as the Duchenne Muscular Dystrophy gene, in embryos conceived through IVF. Only healthy embryos are implanted and parents are assured that their children will not inherit or be a carrier for this disease.
Factor VIII Deficiency is more commonly known as Hemophilia A.
Factor IX Deficiency is more commonly known as Hemophilia B.
Familial Spastic Paraparesis is also known as Hereditary Spastic Paraplegia.
One of the most common inherited causes of mental retardation is the Fragile X Syndrome. Its symptoms include mental retardation of varying severity, learning difficulties, attention deficit hyperactive disorder (ADHD), etc. Affected males generally have enlarged ears, long face and prominent chin, autistic-like behavior and speech impediments. Connective tissue abnormalities may also be present, which may lead to ear infections, flat feet, double-jointed fingers and other skeletal problems. It predominantly affects males, although females may also be affected but with less pronounced symptoms. Affected females also tend to express extreme shyness, attention problems and depression.
Fragile X Syndrome is an X-linked disorder caused by mutations on the FMR1 gene, which is involved in brain development. The FMR1 gene contains a region where the DNA sequence is repeated several times. An individual with a few more than normal number of repeats of this sequence is considered a carrier of this disease. A carrier generally does not show any symptoms. An estimated one in three hundred women are carriers. An individual affected with Fragile X Syndrome has a significantly higher number of repeats than a carrier and is referred to as a “full mutation” patient.
There is currently no cure for Fragile X syndrome. Treatments for Fragile X deal not with the underlying disorder but with the symptoms. These include various medications to address any aggression, anxiety or attention disorder that affected individuals might experience. Patients are usually enrolled in special education, undergo speech and physical therapy. Due to the varying extent of these symptoms, it is important that each patient be carefully diagnosed so a treatment plan may be devised specifically for the needs of that patient.
Couples who are at risk of having a child with Fragile X Syndrome can now take advantage of a new technology called Pre-Implantation Genetic Diagnosis (PGD). Through PGD, an embryo conceived through IVF may be tested for a known genetic defect, such as Fragile X Syndrome. Embryos determined not to be affected are implanted into the uterus. At risk couples can have reassurance that a debilitating disease will not affect their child.
Friedrich’s Ataxia is a form of Cerebellar Ataxia.
Gardner Syndrome is a rare, hereditary disorder involving the colon. It is characterized by multiple growth (polyps) in the colon but affected patients also develop bone and soft tissue tumors. Symptoms of Gardner Syndrome generally appear during the teen years. They may include extra teeth (supernumerary), bony tumors of the skull (osteomas), and fatty cysts or fibrous tumors in the skin (fibromas or epithelial cysts). Individuals affected with Gardner Syndrome may also experience painless rectal bleeding and abdominal cramping. Complications include bowel obstruction and rectal prolapse and/or the growth of other tumors in the GI (gastrointestinal) tract.
Treatment of Gardner Syndrome involves close observation of the patient to monitor growths of the polyps and tumors. A colonoscopy is repeatedly performed to remove the polyps after the onset of the disease. Removal of the colon and rectum is often necessary once the disease has progressed to more advanced stages.
Gardner’s Syndrome is inherited as an autosomal dominant trait; a person who carries the gene for Gardner’s Syndrome will eventually develop the disease. Genetic counseling is strongly recommended to anyone with a family history of this disease. A new test is now available to couples who are at risk of passing the disease on to their child. Pre-Implantation Genetic Diagnosis (PGD) examines the embryos created through IVF for genetic defects such as the Gardner Syndrome gene. Only embryos that do not contain the defective gene are implanted into the mother. This give couples the assurance that they will not pass on a debilitating disease to their children.
Glycogen Storage Disease (GSD) encompasses various metabolic disorders that affect glycogen metabolism. Patients affected with GSD lack or are deficient in enzymes responsible for the conversion of glycogen into glucose. Glucose serves as the primary energy source in the body. It is stored as glycogen, a complex chain of molecules. Glycogen is stored mainly in the liver and muscle cells and is converted into glucose through a series of enzymatic reactions as needed by the body. Various types of GSD are differentiated by the enzyme involved. They are either classified by number, defective enzyme or the individual who first described the condition. There are currently eleven known types of GSD.
Symptoms present in GSD include an enlarged liver, low blood sugar, growth retardation, and an abnormal blood chemistry. Each type of GSD also has its own specific symptoms. Definitive diagnosis can only be made through a biopsy of the affected organ. A primary treatment for individuals with GSD is a well-controlled diet that ensures consistent levels of blood glucose. Symptoms, if properly treated, may subside by the time the patient reaches adulthood. In severe cases, an organ transplant may be the only option for the patient.
GSD is primarily inherited in an autosomal recessive pattern, but a few types have been linked to the X chromosome. These are Type VI or Hers Disease, Type VIII, and Type IX. All three are involved in the activity of the enzyme phosphorylase kinase (PHK) in the liver. PHK is involved in the initial breakdown of glycogen. The X-linked forms of GSD primarily affect males. Couples at risk of having a child with GSD can now take advantage of a new technology called Pre-Implantation Genetic Diagnosis (PGD). PGD tests an embryo for some genetic defects prior to implantation. The sex of the embryo can also be determined. Through this mechanism, the chances of having an affected child is greatly reduced. PGD is a relatively new technology and is continually being improved to include many other disorders. Due to the complex inheritance patterns of diseases, including GSD, a thorough genetic evaluation is strongly recommended to determine whether PGD will be beneficial.
Happle Syndrome is a form of Chondrodysplasia Punctata.
Hemophilia is an inherited bleeding disorder caused by the absence or decreased levels of certain blood clotting factors. In response to an injury such as a cut, the body releases platelets to form a clot at the injury site to prevent further bleeding. Various factors are produced by the platelets and these interact to form a clot. Absence or decreased levels of certain clotting factors causes increased bleeding time and results in Hemophilia. There are two types of Hemophilia and these are classified according to the deficient clotting factor. The more common form, Hemophilia A, is caused by a Factor VIII deficiency, and the less common form, Hemophilia B, is caused by Factor IX deficiency.
Hemophilia is inherited in an X-linked recessive manner and generally affects males. Hemophilia A occurs in 1 out of 5,000-10,000 males worldwide. Hemophilia B is five times less common than Hemophilia A. Hemophilia is characterized by prolonged bleeding time due to the blood’s reduced ability to clot. Skin bruising and painful swelling are also common. Bleeding often occurs at specific sites and carries risks for other complications. Bleeding in the joints may cause arthritis. Muscle bleeding causes swelling and may damage underlying nerves and blood vessels. Bleeding in the head is extremely dangerous; symptoms of this include irritability, drowsiness, headaches, vomiting, nausea and confusion. Neck and throat swelling are also dangerous for it may obstruct breathing. In all of these cases, early detection and treatment is essential. Although Hemophilia is a life long condition and there is currently no cure available, further injury can be avoided if bleeding is detected early. Blood transfusion is a common treatment for patients. Antifibrinolytic agents may also be prescribed along with careful physiotherapy to help strengthen muscles.
Approximately 2/3 of all cases of Hemophilia are inherited, the rest are due to a sporadic genetic mutation. A couple with a familial history of hemophilia should consult with a genetic counselor. They should also be aware and should consider a new genetic test called Preimplantation Genetic Diagnosis (PGD). PGD tests for genetic defects and determines the gender of an embryo prior to implantation. Through this mechanism, the chance of having an affected child can be significantly reduced. A genetic counselor can advise a couple on whether PGD will be of benefit to them. PGD can also test for other genetic disorders and is continually being improved to encompass other hereditary diseases.
Hereditary Motor-Sensor Neuropathy is also known as Charcot-Marie-Tooth Disease.
Hereditary Spastic Paraplegia (HSP) refers to a group of degenerative spinal cord disorders characterized by gradual, progressive weakness and stiffness (spasticity) of the legs. Approximately 10,000 people in the United States are afflicted with HSP.
In HSP, the motor nerves that innervate the lower limbs start to deteriorate. This results in difficulty with balance, weakness and stiffness of the legs, muscle spasms, and dragging of toes while walking. Onset is generally during childhood but occasionally symptoms do not appear until later in life. The severity and progression of the disease also varies, even among families. Other symptoms include shortened Achilles tendon, leg cramps, hyperactive reflexes, and high arch feet (pes cavus).
HSP is classified as either uncomplicated or complicated. Complicated HSP is rare and differs from uncomplicated HSP by the presence of other neurological disorders such as ataxia, epilepsy, optic and retinal neuropathies, mental retardation, ichthyosis and many others. There is no specific test to diagnose HSP. HSP is diagnosed only through careful elimination of other diseases that share common symptoms. Treatment aims to alleviate the symptoms. Physical therapy is important to maintain muscle strength and prevent further muscle weakness. Although the disease is progressive, rarely do patients ever become completely immobile. Assisted devices such as a cane or walker, however, are usually needed.
Within the two forms of HSP are also different types classified according to their mode of inheritance. Autosomal, recessive and X-linked forms of HSP have been found, the most common of which is the autosomal dominant form. Genetic analysis to determine the type of HSP present is now available. Genetic counseling and a thorough genetic evaluation is strongly recommended to families with a history of HSP or any other hereditary disorder. Certain forms of X-linked diseases are more prevalent in one gender over another. A new option, Preimplantation Genetic Diagnosis (PGD), is now available to couples in this situation. PGD tests an embryo for known genetic defects and is able to determine the gender of an embryo prior to implantation. Implanting only specific embrya, either male or female depending on prevalence of that specific disease, will greatly reduce the chances of transmitting the disease. A genetic counselor will determine whether PGD will be of benefit to a couple.
Hers Disease is a form of Glycogen Storage Disease.
Hirschsprung Disease, also known as Congenital Aganglionic Megacolon, is a congenital disorder that affects approximately 1 in every 5,000 births in the United States. It is four times more common among males than females. It is caused by the absence of ganglionic cells in any portion of the intestines or bowel. The ganglionic cells are responsible for the rhythmic contractions necessary for passage of food products. Absence of these cells results in the inability of the bowels to push digested matter and can result in obstruction. Symptoms are often present at birth and include abdominal distension and failure of the meconium to pass through. Other symptoms also include repeated vomiting, chronic constipation and delayed growth due to malnourishment. Enterocolitis, inflammation of the small intestines and colon, is a common complication and may become fatal if not promptly treated.
Diagnosis of Hirschsprung Disease includes a physical examination that reveals a palpable distended abdomen and decreased tone of rectal muscles. Further tests may include abdominal X-rays, biopsy and anal manometry. Most cases of Hirschsprung disease are treated surgically through a temporary colostomy or a removal of the affected segment. A majority of symptoms are relieved through surgery. The outcome is often dependent on the extent of the region affected. Antibiotics may also be prescribed.
Most cases of Hirschsprung Disease are due to sporadic mutations in the genes although people with familial history of Hirschsprung Disease are at an increased risk. They are strongly recommended to undergo genetic counseling and analysis to determine the cause of Hirschsprung Disease and to find out if it is hereditary. Since Hirschsprung Disease is four times more likely to occur among males than females, couples at risk of having an affected child can take advantage of a new genetic test called Preimplantation Genetic Diagnosis (PGD). PGD tests for known genetic defects and can determine the gender of the embryo. Through this mechanism, the chance of having an affected child can be significantly reduced. After a thorough genetic evaluation, a genetic counselor can determine whether PGD will be beneficial. PGD is also available for a variety of other genetic disorders and continues to be improved to include other hereditary diseases.
Huntington’s Disease is an inherited neurological disorder. It is caused by the degeneration of brain cells in certain parts of the brain. An estimated 250,000 individuals in the United States are either affected or are at risk of inheriting the disease from an affected parent. Huntington’s Disease is inherited in an autosomal dominant trait; a parent affected by Huntington’s Disease has a 50-50 chance of passing on the disease to the child. It affects males and females equally and does not predominate in any specific ethnic or socioeconomic background.
Onset of Huntington’s Disease generally begins in mid-life, although symptoms may occur as early as the age of two years. In cases of childhood onset of the disease, children affected rarely live through their teens. Early signs of Huntington’s Disease include depression, mood swings, forgetfulness, clumsiness, involuntary twitching and lack of coordination. As the disease progresses, lack of concentration, diminished short-term memory and judgement, and involuntary movements of the head, trunk and limbs become more evident. Walking, speaking and swallowing become more and more difficult and eventually, an individual with Huntington’s Disease is unable to care for him or herself. Death may occur from choking, infection or heart failure.
At present, there is no cure for Huntington’s Disease. Treatments are directed towards the symptoms and not the disease itself. Various medications are often prescribed to control emotional and movement problems. Antidepressants and tranquilizers may also be prescribed for severe depression and anxiety. Medications are prescribed at the lowest possible dose to prevent or minimize any undesirable side effects. Patients are urged to stay physically active by incorporating an exercise regime, such as walking, in their daily program. Their diet is also strictly monitored to ensure that they are getting the proper amount of nutrients.
Although there is no cure for Huntington’s Disease, couples at risk now have the opportunity to ensure that their child will be free from this disease. A new test, called Pre-Implantation Genetic Diagnosis (PGD) tests for genetic defects, such as the Huntington’s Disease gene, in embryos before implantation. Only embryos without the defective gene will be implanted, considerably reducing the risk of the parent to pass on the disease to the child.
HPRT is more commonly known as Lesch-Nyhan Syndrome.
Ichthyosis is a genetic disorder characterized by dry, thick, scaly skin. The X-linked form of Ichthyosis is relatively common, affecting 1 in 6,000 males in the United States. It does not predominate in any specific ethnic background. It affects primarily males, although a few rare cases were reported in females. Onset of the disease typically occurs at birth or during early infancy. Symptoms include drying and scaling of the skin in the neck, upper trunk and scalp. The face takes on a “dirty-face” appearance - splotchy dirty yellow or dark brown color with dark scales. Corneal opacities may also be present in patients. Ichthyosis is generally not a life threatening or debilitating disease, however, there is no cure and treatment must be administered continuously.
Treatment of Ichthyosis is topical and aims to reduce scaly build up and to moisturize the skin. Severe cases of Ichthyosis can result in extreme dryness and scaling, causing pain and bleeding. For the most part, Ichthyosis is perceived more by patients as a nuisance than a disorder.
There are different forms of Ichthyosis. The X-linked type is caused by steroid sulfatase (STS) deficiency. 90% of patients with X-linked Ichthyosis have either complete or partial deletion of the STS gene located on the X chromosome. X-linked Ichthyosis rarely occurs among females and their symptoms a generally less pronounced. Couples with a familial history of Ichthyosis may take advantage of a new technology called Pre-Implantation Genetic Diagnosis (PGD). PGD tests for some genetic defects and determines the sex of the embryo prior to implantation. Through this, the chances of having an affected child is significantly reduced. In considering PGD, the advice of a genetic counselor and a thorough genetic evaluation is imperative. Due to complex inheritance patterns, a genetic counselor can determine whether PGD will beneficial. For now, the different types of Ichthyosis that have been found to be X-linked are:
Ichthyosis with male hypogonadism
Ichthyosis Follicularis, Atrichia and Photophobia Syndrome
Ichthyosis, Hepatosplenomegaly, and Cerebellar Degeneration
Ichthyosis, Follicular Atrophoderma, Hypotrichosis & Hypohidrosis
However, PGD is continuously being improved so it may in the near future test for more and more genetic diseases, including the non-X-linked form of Ichthyosis.
Please see Ichthyosis for more information.
Please see Ichthyosis for more information.
Please see Ichthyosis for more information.
Please see Ichthyosis for more information.
Kallman Syndrome is a rare X-linked recessive disease characterized by reduced or complete absence of the sense of smell (anosmia), underdeveloped genitalia and sterile gonads. It affects primarily males at an incidence of 1 out of 10,000 and the disease becomes apparent when they fail to begin puberty and to develop secondary sexual characteristics. Kallman Syndrome is primarily an X-linked recessive disease affecting mainly males, although there have been rare cases of Kallman Syndrome among females, in which cases the disease was inherited as an autosomal recessive trait. Impaired or lack of sense of smell is caused by the absence of the olfactory bulbs. Kallman Syndrome also affects the hypothalamus. The hypothalamus produces reduced levels of GnRH, the hormone responsible for the secretion of the hormone LH. LH is the hormone that stimulates gonadal and genital development. In some instances of Kallman Syndrome, GnRH is not produced at all. Decreased or absence of GnRH also causes reduced levels of other hormones including estrogen and testosterone. Patients are therefore at a greater risk for osteoporosis and brittle bone disease. Kallman Syndrome may also be associated with X-linked Ichthyosis and Conradi-Hunermann Syndrome.
Other symptoms also associated with Kallman Syndrome include gynecomastia, bimanual synkinesis (one hand copying the movements of the other hand), shortened fourth metacarpal bone and an absent kidney.
The life span of an affected individual is generally not altered by Kallman Syndrome. Treatment of this disease involves hormone, estrogen or testosterone, replacement, and pulsatile GnRH or repeated hCG injections. Patients may undergo fertility treatment later in life if they desire to have children.
Couples with a familial history of Kallman Syndrome may reduce their risk of having a child affected with this disease through a new technology called Preimplantation Genetic Diagnosis (PGD). In PGD, embryos are tested for genetic abnormalities and their gender is determined. Only genetically healthy embryos are implanted. Through this mechanism, the chances of having an affected child can be greatly reduced. Due to complex inheritance patterns couples at risk should seek the advice of a genetic counselor to determine whether PGD will be beneficial. PGD can currently test for a variety of other genetic disorders and is continually being improved to include other genetic diseases.
Kelley-Seegmiller Syndrome is also known as Lesch-Nyhan Syndrome.
Kennedy Disease, also known as Spinal and Bulbar Muscular Atrophy (SBMA), is a rare subtype of Spinal Muscular Atrophy. Spinal Muscular Atrophy is a degenerative neuromuscular disorder that affects proximal muscles involved in voluntary activities such as walking, head and neck control and swallowing. Kennedy Disease is a rare, adult-onset type of Spinal Muscular Atrophy. It affects approximately 1 in 50,000. Due to its symptoms, it is often misdiagnosed as Lou Gehrig’s Disease. A definitive diagnosis can be made through DNA analysis.
Kennedy Disease is a slow, but progressive disease. Onset of Kennedy Disease typically occurs during thirty years of age but may appear in their fifties. Early symptoms include severe muscle cramps, and weakness of the hip and shoulder muscles. Muscles of the face, lips, tongue, mouth, throat, vocal cords, trunk and limbs may also be affected. The patient often experiences uncontrollable twitching of these muscles, followed by weakness and atrophy. Physical manifestations include difficulty or inability to chew, swallow and breath, unusually large calves, and a scalloped appearance of the tongue. Other complications of Kennedy Disease include swelling of the breasts (gynecomastia), endocrine disorders such as diabetes and gonadal atrophy. There is no cure or proven effective treatment for Kennedy Disease. Management of the disease includes reducing risks for injury in daily life and at work. As the disease progresses, wheelchair may be necessary.
Kennedy Disease is caused by an abnormally high number of CAG repeats in the androgen receptor gene on the X chromosome. The exact mechanism of how this affects muscle function is unknown. Transmission of Kennedy Disease to offspring may be prevented through a new technology called Pre-Implantation Genetic Diagnosis (PGD). PGD tests embryos for genetic defects and determines the sex of the embryos prior to implantation. Due to its inheritance pattern, Kennedy Disease is more prevalent and symptoms more pronounced in males than in females. A thorough genetic evaluation can determine whether PGD will be beneficial to families. With advances in genetic research, PGD is continuously being improved so it may eventually test for many more genetic conditions including all forms of Spinal Muscular Atrophy.
Lesch-Nyhan Syndrome is a rare X-linked recessive disorder affecting approximately 1 out of 400,000 males. It is characterized by excessive levels of uric acid in the blood, which may eventually lead to kidney damage. Its symptoms include muscle spasms that cause jerky movements, and self-injurious behavior such as compulsive biting of lips and tongue. The pathology for these symptoms is not clearly understood. Lesch-Nyhan Syndrome may also lead to physical and mental retardation as well as Nephrolithiasis, urinary tract stones and may impact brain development.
Symptoms of Lesch-Nyhan Syndrome usually present themselves early in infancy. Sand-like crystals appear in diapers of infants. Infants affected with Lesch-Nyhan Syndrome may also seem unusually irritable and unable to lift his or her head at age 4-6 months. They may also display uncontrolled writhing motions and have poor motor development.
There is currently no cure for Lesch-Nyhan Syndrome. Treatments include medication to lower uric acid levels in the blood. Patients must closely monitor their fluid intake to ensure that they are well hydrated. Parents with children inflicted with Lesch-Nyhan Syndrome must take special precautions in their household, such as padding any sharp corners, to prevent further injury when their children uncontrollably engage in self-destructive behavior.
Individuals with Lesch-Nyhan Syndrome and their families are recommended to undergo genetic counseling and testing. Lesch-Nyhan Syndrome rarely occurs among females and female carriers typically do not show any symptoms but have a 50% chance of passing on the defective gene to her children. A new test is now available to reduce the risk of passing on a genetic disorder, such as Lesch-Nyhan Syndrome, to children. This test is called Preimplantation Genetic Diagnosis (PGD). PGD tests an embryo for genetic defects and determines its sex prior to implantation. Through this mechanism, the chance of having an affected can be significantly reduced. Inheritance patterns can be very complex therefore a thorough genetic evaluation by an experienced genetic counselor can determine whether PGD will be beneficial. PGD is also available for a number of other genetic diseases and is continually being improved to include others.
Lou Gehrig’s Disease is also known as Amyotrophic Lateral Sclerosis.
Mitochondrial Myopathy is a form of Myopathy.
Myopathies refer to a class of degenerative skeletal muscle disease that is not caused by nerve dysfunction. Myopathies cause progressive weakness and wasting away of skeletal muscles. The causes for Myopathies vary. They could be hereditary, an inflammatory response, or the result of an endocrine disorder. The different types of Myopathies are classified according to their causes.
Genetic Myopathies include Central Core Disease, Centronuclear (Myotubular) Myopathy, Myotonia Congenita, Nemaline Myopathy, Paramyotonia Congenita, Periodic Paralysis and Mitochondrial Myopathies. These forms vary by symptoms, severity and genetic mutation. Both dominant and recessive modes of inheritance are also present. Certain forms of Centronuclear Myopathy, also known as Myotubular Myopathy, have been found to be X-linked and primarily affects males.
Symptoms common among myopathies include weakness of the voluntary muscles of the arms, legs, and trunk, drooping upper eyelids, foot drop, facial weakness and lack of reflexes in the affected muscles. Some symptoms may be transitory. Although there is no effective cure or treatment for them, myopathies are hardly ever debilitating.
Due to the varying forms and causes of Myopathies, determining the form of Myopathy the individual patient has is crucial in providing the proper treatment. Diagnosis includes a thorough physical examination, measurement of potassium in the blood, muscle biopsies and an electromyogram (EMG). In genetically based Myopathies, the affected families are strongly advised to consult a genetic counselor. Couples with a history of X-linked form of Myopathy may benefit from a new procedure called Preimplantation Genetic Diagnosis (PGD). In hereditary disorders that are predominant in one gender, implantation of gender-specific embryos through PGD will greatly reduce the chance of having an affected child. A genetic counselor, after conducting a thorough genetic evaluation, can determine whether PGD will be beneficial. PGD is currently available for a number of genetic disorders. PGD is continually being improved in order to test for other genetic disorders.
Myotonia Congenita is a form of Myopathy.
Myotubular Myopathy is a form of Myopathy.
Nemaline Myopathy is a form of Myopathy.
Nephrolithiasis is a fairly common stone disease of the kidney. It is more predominant among male Caucasians than any other ethnic group. Approximately 1 in 8 will be diagnosed with Nephrolithiasis in their lifetime. Age of onset could be as early as teen years and as late as fifty years old. The earlier the onset of the disease, the greater the chance of a recurrence.
Nephrolithiasis is caused by increased concentrations of calcium, oxalates and uric acid that accumulate in the kidney. Renal tubular damage may also contribute to stone formation. Although it originates in the kidney, the stone may get lodged in the urinary tract. About 80% of the stones, if small, pass spontaneously. Larger stones are likely to block the flow of urine, and renal failure and possible loss of kidney function may result if obstruction, caused by the stone, is not cleared within a week. Symptoms of Nephrolithiasis include sudden, sharp and quite severe pains usually on the sides of the abdomen, nausea, vomiting, frequent urination accompanied with intense pain, and microscopic hematuria (blood in the urine). Patients may also become hypertensive due to the pain. A fever maybe an indication of an infection. It is important for patients to be sufficiently hydrated. That is the main concern of treatments. Surgery may be necessary to remove the stone. Strong pain medication may also be frequently prescribed.
A form of Nephrolithiasis has been traced to a mutation on the X chromosome. Couples whose families have a history of kidney stone disease and renal failure should consider a new genetic technology called Pre-Implantation Genetic Diagnosis (PGD). PGD tests an embryo for genetic abnormalities and can determine its gender prior to implantation into the uterus. Through this, the chances of having an affected child can significantly be reduced. Couples at risk of having a child with a hereditary disorder should seek the advice of a genetic counselor. Due to complex inheritance patterns of genetic disorders, they can determine whether PGD will be beneficial. PGD is also available for a variety of other hereditary disorders and is continually being improved in order to test for more and more genetic diseases.
Paramyotonia Congenita is a form of Myopathy.
Parkinson’s Disease is a degenerative neurological disorder that affects approximately 500,000 people in the United States. An estimated 50,000 new cases are reported each year. It has garnered much attention in recent years due to the public disclosure of well known figures such as Muhammad Ali and Michael J. Fox to be sufferers of this disease. Much research is currently underway to understand Parkinsonism.
Parkinson’s Disease affects the area in the brain called the substantia nigra. This region produces the neurotransmitter called dopamine, the chemical messenger crucial for muscle movement. Degeneration of the substantia nigra leads to decreased levels of dopamine. A cardinal symptom associated with Parkinson’s Disease is the trembling of hands. There are however other earlier symptoms associated with Parkinson’s Disease that are often ignored. These include feeling unusually anxious, irritable, fatigued and have difficulty in sleeping. As the disease progresses, patients may also experience increased and often times uncontrollable trembling, slurring of words, slowed movement (bradykinesia), stiff trunk and limbs, less facial expression, trouble swallowing, and problems with balance and coordination. Reasoning ability is for the most part, unaffected.
Diagnosis for Parkinson’s Disease is made through careful observation by the physician. There is no laboratory test that can definitively diagnose for Parkinson’s Disease. There is also no cure for Parkinson’s Disease. A common medication prescribed is levodopa, or L-dopa. L-dopa is a precursor to dopamine. The brain breaks down L-dopa to replenish the low levels of dopamine. To some, the effects of this drug is almost immediate. However, L-dopa does not reverse or stop the deterioration of the brain cells and increased dosage of L-dopa is eventually inevitable. Regular exercise and a well-balanced diet is also strongly recommended.
The exact cause of Parkinson’s Disease is unknown but is believed to be multifactorial. Genetics is strongly suspected in some cases, but it is generally thought that something must trigger it. Parkinson’s may be triggered by chemicals in the environment or even viral infections. It affects males more than females and has been found to occur in certain families, but a majority of cases are sporadic. Families with high incidence of Parkinson’s Disease are strongly encouraged to undergo genetic counseling and a comprehensive pedigree analysis to rule out a genetic cause for this disease. In families where Parkinson’s Disease only occurs in a specific gender, a new genetic test may be beneficial. Preimplantation Genetic Diagnosis (PGD) tests for genetic abnormalities and can determine an embryo’s gender prior to implantation. This can significantly reduce the chance of having an affected child in these cases. A genetic counselor should be consulted whether PGD will be beneficial. PGD is also available for a variety of other hereditary disorders.
Hypokalemic and Hyper Kalemic forms of Periodic Paralysis are forms of Myopathy.
Peroneal Muscle Atrophy is also commonly known as Charcot Marie Tooth Disease.
Polycystic Ovary Syndrome, also known as Stein-Leventhal Syndrome, is an endocrine disorder that affects approximately 3% of women. Common characteristics of Polycystic Ovary Syndrome include an accumulation of cysts on the ovaries, an appreciable increase in male hormone levels, chronic anovulation and irregular menstruation. Other symptoms present also include excess facial and body hair, male pattern baldness, acne, skin discoloration, obesity and infertility.
Treatments are aimed at alleviating symptoms. These include medication to correct anovulation and to establish a regular menstrual cycle, and topical and oral medication for acne. A regular exercise regime and a healthy diet may also be prescribed for excessive weight gain. In some instances, weight loss reduce the levels of androgens and counter its effects. In some cases, surgery is necessary to treat Polycystic Ovary. Women diagnosed with Polycystic Ovary Syndrome are at a greater risk for endometriosis, diabetes, cardiovascular disease and uterine cancer.
Diagnosis of Polycystic Ovary Syndrome entails comprehensive tests of hormone levels and gynecologic ultrasound study. Polycystic Ovary Syndrome has common symptoms with other disorders so a thorough examination is necessary. Not all symptoms are necessary for the diagnosis of Polycystic Ovary Syndrome. Women may have polycystic ovaries and still have regular menstruation and the reverse can also be true. Physicians look at menstrual and hormonal abnormalities and should consider the complete clinical picture to make the diagnosis.
Although the exact cause of Polycystic Ovary Syndrome is unknown, it does tend to run in families. Women with Polycystic Ovary Syndrome or who have familial history of this disorder might consider a new genetic test called Preimplantation Genetic Diagnosis (PGD). Unlike other genetic testing available, PGD tests for genetic defects and can determine the gender of an embryo prior to implantation. In Polycystic Ovary Syndrome, implanting only male embryos will ensure the couple that the disorder will not be passed on. The advice of a genetic counselor should be sought to determine whether PGD will be beneficial. PGD is also available for a number of other genetic disorders and is continually being improved to test for other hereditary diseases.
Prostate Cancer is one of the most common cancers among men in the United States. This year alone, an estimated 185,000 men will be diagnosed with Prostate Cancer and around 30,000 men will die from it. The cancer originates in the prostate, a walnut-size gland located at the base of the urinary bladder. Early stages of Prostate Cancer are generally asymptomatic. As the disease progresses, frequent but weaker urination becomes evident. Swollen lymph nodes in the groin area, hematuria (blood in the urine), impotence and pain in the groin, spine, hips and ribs may be present in advanced stages of Prostate Cancer. However, these symptoms may be associated with a variety of other diseases.
Men may be tested for Prostate Cancer two ways. The first is a simple blood test called PSA (prostate-specific antigen) test. The other is a digital rectal exam (DRE) performed by a physician. Testing is highly recommended to men over the age of 40 years, especially if they have a family history of Prostate Cancer. A definitive diagnosis is made through a core needle biopsy.
Affected individuals have a variety of options regarding treatment. These include the removal of the prostate, radiation to kill cancerous cells, and hormonal therapies to slow the growth of malignant cells.
The exact cause of Prostate Cancer is unknown. Risk of Prostate Cancer increases with age and is more predominant among African-Americans. Men with familial history of Prostate Cancer are at an increased risk, lending support to a belief that Prostate Cancer may be hereditary in some cases. Some cases of Prostate Cancer have been traced to genetic abnormalities. In diseases that are more prevalent in one gender than the other, as in the case of Prostate Cancer, where it exclusively occurs among males, a new test may help reduce the chances of having an affected child. In Preimplantation Genetic Diagnosis (PGD), embryos are tested for genetic abnormalities and their gender determined prior to implantation. Using PGD to implant only female embryos will ensure the couple with a strong family history of this disease that their child will not be affected with Prostate Cancer. Couples should consult with a genetic counselor about their actions. PGD can currently test for a variety of diseases, inclusive of X-linked diseases, and those that primarily affect a specific gender. PGD is continuously being improved so we may be able to test for more and more genetic disorders in the near future.
Retinitis Pigmentosa refers to a group of disorders characterized by the degeneration of the retina that may eventually lead to blindness. The retina is located on the interior surface of the eyes and consists of several layers. Cones are specialized cells in the retina that are responsible for sharpness, and central and color vision. Cones are localized in the area called fovea. Surrounding the cones are other specialized cells called rods. Rods are responsible for peripheral and night vision. Retinitis Pigmentosa is a progressive disease, initially only affecting the rods in the retina. As the rods start to deteriorate, night vision becomes impaired. Peripheral and color vision also becomes compromised. Onset of the disease typically occurs during early adolescence. In some instances, severe deterioration of the rods and cones results in blindness.
There is no known effective cure or treatment for Retinitis Pigmentosa. Administration of Vitamins A and E have been found to slow progression but only in a small number of patients. Only quite high amounts of Vitamins A and E have been found more effective in these patients. Such amounts may be toxic, thus special care must be exercised during this treatment. Affected individuals must have limited exposure to bright sunlight and must wear sunglasses with infrared and ultraviolet protections.
There are many forms of Retinitis Pigmentosa, some have genetic causes and modes of inheritance in these forms varies. The X-linked forms are generally more severe than the other forms and are more pronounced in males than in females. Among the different forms of Retinitis Pigmentosa, these have been found to be X-linked:
Retinitis Pigmentosa 1 Retinitis Pigmentosa 13
Retinitis Pigmentosa 6 Retinitis Pigmentosa 15
Retinitis Pigmentosa 8 Retinitis Pigmentosa 24
Retinitis Pigmentosa 10
Couples with familial history of Retinitis Pigmentosa should consult with a genetic counselor regarding the various options available to them. A new test now available is called Preimplantation Genetic Diagnosis (PGD). Testing for genetic abnormalities as well as gender determination of embryos prior to implantation can be accomplished through PGD. Certain X-linked diseases are more prevalent in one gender over another. Knowing this and utilizing PGD can reduce the chances of having an affected child. PGD is available for a variety of other genetic disorders. It is continually being improved to include all other forms of Retinitis Pigmentosa and other hereditary diseases.
Sickle Cell Disease is a genetic disorder of the blood, affecting approximately 72,000 individuals in the United States. It is characterized by anemia, frequent infections, and unpredictable and severe pains in the back, chest, abdomen and limbs. Sickle Cell Disease is most common among those of African descent. An estimated 8 to 12 percent of African Americans carry the sickle cell gene. It is also fairly common in people from Mediterranean countries, Middle East and India.
Symptoms of Sickle Cell Disease may appear as early as in 6 months of age and include infections, pain and swelling of hands and feet, enlargement of the abdomen and heart. It is caused by a defective gene, producing an abnormal form of hemoglobin. Hemoglobin is the component of the red blood cell responsible for oxygen transport from the lungs to the tissues. Red blood cells do not retain their normal disc shape once they release oxygen, instead they take on a sickle shape. Their distorted shape makes it difficult for the red blood cells to pass through vessels, preventing oxygen and vital nutrients from reaching organs and tissues. This manifests into intense pain and patients also become vulnerable to infections. Blood flow to the brain may be affected and could lead to a stroke.
Sickle Cell Disease is inherited as an autosomal recessive trait. Both parents must be carriers and each must pass on the sickle cell gene for the child to be affected. Individuals who carry the trait generally do not show any symptoms. A simple blood test can determine whether an individual is a carrier or not. People who are from an at risk population should be tested. Diagnosis of the disease itself is accomplished through a test called electrophoresis.
There is no cure for Sickle Cell Disease but various treatments are currently available. Treatments are geared toward minimizing pain, reducing organ damage, and preventing infection. These include pain medications, antibiotics for infections and high fluid intake to prevent dehydration. Blood transfusions treat anemia by replenishing the red blood cell supply in the body. In a small number of children, bone marrow transplant has cured them of sickle cell disease but careful consideration must be taken in screening prospective donors, especially relatives, to ensure that they are not affected or are not carriers of the sickle cell gene.
Couples at risk for passing on Sickle Cell Disease should consider a new test called Pre-Implantation Genetic Diagnosis (PGD). PGD ensures a couple that their children will not inherit the disease.
Spinal and Bulbar Muscular Atrophy is more commonly known as Kennedy’s Disease.
Stein-Leventhal Syndrome is also known as Polycystic Ovary Syndrome.
Strumpel Disease is also known as Hereditary Spastic Paraplegia.
Tay-Sachs Disease is a hereditary metabolic defect. Individuals affected with Tay-Sachs lack the enzyme hexosaminidinase-A, the enzyme responsible for fat metabolism in the brain. Absence of this enzyme results in the accumulation of fat in the brain and leads to in irreversible nerve damage. An infant affected with Tay-Sachs Disease may appear normal and healthy at birth. Symptoms generally do not appear until the 3rd-6th month. Once symptoms appear, progression of the disease is rapid. A majority of children affected live only up to their fifth year.
Most cases of Tay-Sachs Disease occur among infants. Clinical features of Tay-Sachs Disease include loss of response to the environment, blindness, mental deterioration, paralysis and epileptic seizures. An early sign for Tay-Sachs Disease is the appearance of a cherry-red spot on the retina of the eye. There is no known cure nor is there an effective treatment for Tay-Sachs Disease. Much of the efforts is geared towards making the child with Tay-Sachs Disease as comfortable as possible. Diets of children affected are strictly monitored to ensure that they are getting the sufficient nutrients. There have been some cases of adult onset of Tay-Sachs Disease as well. Symptoms of this include an unsteady gait (ataxia), inability to move smoothly (dysarthria), muscle weakness and recurrent psychosis. Adult onset of Tay-Sachs Disease is often misdiagnosed.
Tay-Sachs Disease is inherited as an autosomal recessive trait. It is primarily found among Jews of Eastern European descent where one out of 27 is a carrier. Similar rates are also found among French Canadians, Cajuns and in Amish communities. Screening for the Tay-Sachs gene is accomplished by a simple blood test that measures Hex-A in the blood. Lower than normal levels of Hex-A in an individual indicate that he or she is a carrier. This test is strongly recommended to those at risk ethnic groups listed above. Family history of the disease is often not comprehensive due to the high mortality rates among infants affected, and is not a necessary prerequisite for testing. Anyone who is found to be a carrier of the disease should alert relatives and encourage them to be screened as well.
A new technology is now available to couples at risk of passing on Tay-Sachs Disease to their children. Pre-Implantation Genetic Diagnosis (PGD) tests for genetic defects such as the Tay-Sachs gene in embryos conceived through IVF. Only genetically healthy embryos are implanted. Couples, through PGD, can be assured of having disease-free children.
Thrombocytopenia is a bleeding disorder caused by decreased levels of platelets in the bloodstream. Decreased platelets may be caused by decreased platelet production in the bone marrow, increased levels of platelets in the spleen and higher than normal breakdown of platelets. Patients with Thrombocytopenia tend to bruise easily and have prolonged bleeding times.
Diagnosis of Thrombocytopenia often starts with a low blood platelet count. The functions of the spleen and bone marrow are carefully monitored to determine the reason behind the decreased levels of platelets. This is also necessary to rule out any other blood disorders, cancers or other diseases.
Treatment of Thrombocytopenia depends on severity and the organ affected. Platelet transfusion is commonly done to replenish the platelet supply. Drugs such as steroids may also be prescribed to maintain healthy platelet levels. In severe cases of spleen enlargement, the spleen may be partially or completely removed.
The causes of Thrombocytopenia are varied. Some are idiopathic while others have genetic causes. Some instances of Thrombocytopenia have been traced to a defect in the WAS gene on the X Chromosome. Individuals and their families should consult with a genetic counselor to determine whether their form of Thrombocytopenia is genetically linked. If so, they could take advantage of new genetic testing now available to reduce the chances of passing on the disorder to their children. One of these tests is Preimplantation Genetic Diagnosis (PGD). PGD is different from other prenatal testing for it tests an embryo prior to implantation. Implanting only genetically healthy embryos will greatly reduce the chance of having an affected child. Couples should seek the advice of a genetic counselor. After a thorough genetic evaluation, the genetic counselor can determine whether PGD will be beneficial. PGD is also available for many other genetic abnormalities and with advances in genetic research is continually being improved to include many other disorders.
Von Willebrand Disease is the most common hereditary blood disorder that is characterized by prolonged bleeding time. Approximately 1% of the US population is affected by Von Willebrand Disease. There are different subtypes of Von Willebrand Disease, namely Types 1, 2A, 2B, 2M, 2N, and 3. Type 1 is mildest form as well as the most common. Type 3 on the other hand, is rare and is the most severe form. They are classified according to the genetic mutation present.
In response to an injury such as a cut, the body releases platelets to form a plug at the injury site and to prevent further bleeding. Various factors are released by platelets including von Willebrand Factor (vWF) to aid in the clotting process. Reduced levels or reduced functioning of vWF results in prolonged bleeding times in individuals affected with Von Willebrand Disease. Patients with a severe form of Von Willebrand Disease may also suffer from spontaneous nose bleeds and bleeding from mouth, stomach, intestines or urinary system. Increased bleeding time, reduced levels and functioning of vWF and decreased levels of another clotting factor, Factor VIII, must be present for a definitive diagnosis of Von Willebrand Disease.
The most common treatment for Von Willebrand Disease is replacement therapy. Factor VIII and vWF replacements are administered to the patients. Other drugs may also be administered to aid in the clotting process of the patient.
Due to varying types of Von Willebrand Disease, families with a history of this disease should seek genetic counseling and request a comprehensive genetic analysis to determine the type of Von Willebrand Disease and the mode of its inheritance. X-linked forms of Willebrand Disease have been found and families with this particular type of Von Willebrand Disease may benefit from a new test called Preimplantation Genetic Diagnosis (PGD). PGD tests for genetic abnormalities and determines the gender of an embryo prior to implantation. Some X-linked forms of Von Willebrand Disease may be more prevalent in one or the other gender. In such cases, knowing the gender of the embryos through PGD and implanting only the healthy ones will greatly reduce the chance of having an affected child. A experienced genetic counselor can determine whether PGD will be beneficial. PGD can currently test for a number of genetic disorders. It is continually being improved so it may someday test for all forms of Von Willebrand Disease and other genetic disorders as well.
