Around the world distinct ethnic groups are known to have an increased risk for particular genetic diseases. In the Ashkenazi Jewish (Eastern European) population several inherited diseases are known.
There are a number of other disorders that occur more often in the Ashkenazi Jewish population for which carrier testing is also available. Interested couples can have a blood test to learn about their chances of having a child affected with one of these conditions.
Cystic fibrosis is a chronic disorder that primarily involves the respiratory, digestive and reproductive systems. Symptoms include pneumonia, diarrhea, poor growth and infertility. Some people are only mildly affected, but individuals with severe disease may die in childhood. The average lifespan today is 32 years, but may improve as scientists search for better treatments. Cystic fibrosis does not affect intelligence. Learn about genetic testing for cystic fibrosis.
Tay-Sachs disease is increased in frequency in families of Ashkenazic Jewish ancestry, and also in individuals of French-Canadian and Cajun ancestry.
Canavan disease is a disorder which causes brain and nervous system degeneration. Individuals with Canavan disease usually die in early childhood. At this time there is no treatment.
Familial dysautonomia is a nervous system disorder that causes vomiting, sweating, decreased pain sensitivity, and unstable blood pressure or temperature. Individuals often have normal intelligence, but may have learning disabilities. Symptom management improves quality of life, but only 50% of affected individuals will reach age 30.
Bloom Syndrome causes poor growth, poor immune system function and a high rate of cancer. Individuals with Bloom syndrome usually die from cancer before age 30. Bloom syndrome does not affect intelligence.
Fanconi Anemia Group C
Fanconi anemia group C is a disease that causes anemia, short stature and, oftentimes, abnormalities of the heart, kidneys or limbs. Some individuals have learning disabilities or mental retardation. Patients have a high rate of cancer, especially leukemia.
Gaucher disease is caused by an enzyme deficiency. Symptoms are variable and may include fatigue, enlarged liver and spleen, easy bruising and bleeding, bone pain and fractures. The most common form of Gaucher disease is treatable by enzyme replacement therapy. In the most severe form, which occurs much less frequently, the brain and nervous system are also involved.
Glycogen Storage Disease Type 1a
Glycogen storage disease type 1a is a disorder which causes severe low blood sugar, enlarged liver, delayed growth and bleeding. Treatment consists of a strict diet and continuous tube feedings of glucose.
Maple Syrup Urine Disease
Maple syrup urine disease (MSUD) is a disorder which causes certain amino acids to accumulate in the blood. The disease name refers to the characteristic odor of the urine. Without diagnosis and treatment, classic MSUD leads to mental retardation, physical disabilities, seizures and death. Treatment consists of a strict, lifelong special diet to attempt to control the accumulation of amino acids in the blood.
Mucolipidosis Type IV
Mucolipidosis type IV affects the brain and nervous system. Symptoms begin in the first year of life, resulting in mental and physical retardation, and impaired vision. At this time there is no treatment.
Niemann-Pick Disease Type A
Niemann-Pick disease type A causes poor growth, enlarged liver, and mental and physical deterioration. Individuals with Niemann-Pick disease type A usually die by age 4. At this time there is no treatment.
TABLE 1: Carrier Frequencies and Detection Rates in Ashkenazi Jewish Population
|DISEASE||CARRIER FREQUENCY*||DETECTION RATE**|
|Cystic fibrosis||1 in 26||97%|
|Tay-Sachs disease||1 in 30||98%|
|Canavan disease||1 in 57||98%|
|Familial dysautonomia||1 in 30||99.5%|
|Bloom syndrome||1 in 100||97%|
|Fanconi anemia group C||1 in 89||99%|
|Gaucher disease||1 in 15||95%|
|Glycogen storage disease type 1a||1 in 71||99%|
|Maple syrup urine disease||1 in 81||99%|
|Mucolipidosis type IV||1 in 122||96%|
|Niemann-Pick disease type A||1 in 90||95%|
*Carrier frequency is the proportion of individuals in a population who have a single copy of a recessive gene mutation. A carrier frequency of 1 in 26 means that, on average, out of 26 Ashkenazi Jewish individuals, 1 would be a carrier and 25 would not be carriers.
**Detection rate is the percentage of carriers that are identified by the test. A 95 percent detection rate means that 95 percent of carriers will have their gene mutation identified by this test and 5 percent of carriers will have a mutation that cannot be detected by the test.
If someone in your family has one of these genetic diseases or is known to be a carrier, your chances of being a carrier would be higher than the general Ashkenazi Jewish frequencies listed above.
How are genetic diseases passed from one generation to the next?
Genetic disorders are caused by mutation in genes. Every person has two copies of a gene, one inherited from each parent. To have one of the diseases described in this brochure, an individual must have two copies of the abnormal gene. These are called “autosomal recessive” genetic diseases.
What is a carrier?
A carrier is a person who has one normal copy of a gene and one abnormal copy. Having one normal gene is enough to prevent the disease. However, if both parents are carriers of the same abnormal gene, there is a chance that each parent will pass his or her abnormal gene to their baby. If the baby inherits two copies of the abnormal gene, the baby will have the disease. Couples may decide to have carrier testing to find out if they are carriers, and therefore are at risk of having a baby with one of these genetic diseases.
TABLE 2: Carriers and Gene Inheritance (N= Normal; D=Defect/Abnormal)
|Carrier Mother||Carrier Mother|
|Carrier Father||N|| N/N|