Jewish Genetic Diseases Screening Program:
Diseases for Which Screening Is Available
The diseases for which screening is available at the Center for Jewish Genetic Diseases are described, in brief, below. We have provided frequency of occurrence and detection rate for each condition.
Tay-Sachs Disease is a disorder in which the central nervous system progressively degenerates. This degeneration causes loss of coordination, seizures, difficulty swallowing, and poor pulmonary function. Symptoms usually appear at about 6 months of age. Eventually, children with Tay-Sachs disease become blind, severely mentally retarded, paralyzed, and unaware of their surroundings. There is no treatment, and average life expectancy is 3-5 years.
About 1 in 25 Ashkenazi Jewish individuals is a Tay-Sachs carrier. The gene is also relatively common in the French Canadian population and the Cajun community in Louisiana.
Carrier screening involves analysis of the enzyme responsible for Tay-Sachs disease. The detection rate for carriers is approximately 99%.
Familial Dysautonomia (FD) is a severe disease of the autonomic nervous system. Autonomic nerves control functions such as swallowing, sweating, and the ability to cry with tears and to sense pain. Individuals with FD may have severe gastrointestinal problems and pulmonary complications such as pneumonia. The carrier frequency in the Ashkenazi population is 1/35. Testing for two common mutations provides a carrier detection rate of 99.5%.
Canavan Disease is a progressive disease of the central nervous system for which there is no treatment. Symptoms, which begin in infancy, include poor head control, generalized weakness, and enlarged head size. Affected infants also develop seizure, regression of early developmental milestones, and severe mental retardation. Canavan disease is typically fatal in childhood, and there is no treatment.
The carrier frequency in the Ashkenazi Jewish population is about 1 in 40. Testing involves analysis of common mutations in this gene, and the detection rate is about 97%.
Niemann-Pick Disease is a severe neurodegenerative condition of infancy that cannot be treated. Symptoms, including loss of brain function and enlargement of the liver and spleen, appear by about 6 months of age. Average life expectancy is about 2-3 years of age.
Approximately 1 in 70 Ashkenazi Jewish individuals carries the Niemann-Pick disease gene. Testing for the common mutations allows a detection rate for carriers of about 95%.
Gaucher Disease (Type I) is characterized by enlargement of the spleen and liver as well as blood abnormalities, including anemia, easy bruising, and impaired clotting. In addition, there are orthopedic problems, such as bone and joint pain and an increased susceptibility to bone fracture. The age of onset of symptoms is variable, with some individuals showing symptoms in childhood and others remaining relatively symptom-free into their 50s or 60s. The severity of symptoms varies among patients. Enzyme replacement therapy has been developed in recent years and has been highly effective in reversing some symptoms and reducing the severity of others.
Type I Gaucher disease is the most common genetic disorder in the Ashkenazi Jewish population, with a carrier frequency of about 1 in 19. Analysis of common mutations allows a detection rate for carriers of about 95%.
Cystic fibrosis (CF) is a progressive, lifelong condition in which the glands that produce mucus, sweat, and intestinal secretions do not function properly. This dysfunction results in thick mucus accumulation in the lungs, leading to breathing difficulty and infection. CF also causes poor digestion, and males with this disease are usually infertile. There is no cure for CF. Supportive reatments are available to help improve quality of life, and average life expectancy has improved over the years. While some babies with CF still die in infancy, many patients with CF live into their 20s and 30s.
CF is found in all ethnic groups. It is most common among Caucasians, Jewish and non-Jewish alike, with a carrier frequency of about 1 in 25. By testing for some of the more common mutations, 96% of Ashkenazi Jewish CF carriers can be identified, as can 85% of non-Jewish Northern European CF carriers.
Fanconi Anemia (Type C) is a chronic disease associated with short stature, bone marrow failure, congenital malformations, and a predisposition to leukemia. For some children, the condition may also involve learning disabilities or mental retardation. The carrier frequency in the Ashkenazi Jewish population is about 1 in 90. Testing for one common mutation provides a carrier detection rate of approximately 95%.
Bloom syndrome is a condition in which children grow poorly, have frequent infections, and may have learning disabilities. As adolescents and young adults, individuals with Bloom syndrome are predisposed to develop common cancers such as breast cancer, colon cancer, and leukemia. The carrier frequency in the Ashkenazi Jewish population is approximately 1 in 100. Testing for one common mutation allows for a carrier detection rate that is greater than 95%.
Mucolipidosis Type IV (MLIV) is a severe neurodegenerative condition that is characterized by a variable degree of growth and psychomotor retardation. In addition, many patients have abnormalities of the cornea and retina. Most patients never develop the ability to speak or walk and remain at the developmental level of 1 to 2 years of age. The carrier frequency in the Ashkenazi population is approximately 1 in 125. Testing for two mutations provides a carrier detection rate of 96%.