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June 25, 2004/Tamuz 6 5764, Vol. 56, No. 40
Know your Jewish genetic disorders
DR. STEVEN WININGER
Special to the Jewish News
It's always a delight when one of my patients indicates that she and her husband are planning to start a family. I always spend some time learning about the ethnic background of my patients because almost every ethnic, racial or demographic group suffers disproportionately from certain genetic diseases. For example, it has been estimated that 25 percent of Ashkenazic Jews (those of Eastern European descent) is a carrier of one of several genetic conditions.
Most of these diseases are autosomal recessive, which means that a disease can only be passed on if both parents are carriers. Although carriers are not affected by the disease, if both members of a couple are carriers of the same disease gene, there is a 25 percent chance in each pregnancy for a child to inherit the disease. There is also a 50 percent chance of having a child who is a carrier like themselves and a 25 percent chance of having a child who is neither affected nor a carrier.
Fortunately, there are extremely accurate blood tests that can identify carriers. Both amniocentesis, which is generally performed 15 to 18 weeks into a pregnancy, and chorionic villus sampling (CVS), which is usually performed at 10 to 12 weeks into a pregnancy, can determine whether a fetus has inherited any of these diseases.
It is important for Jewish patients to learn about genetic disorders that occur more frequently within the Jewish population, or, as in the case of cystic fibrosis, at a very high rate for all Caucasians from Northern Europe, including Ashkenazic Jews. Among the Ashkenazic Jewish population, these diseases include:
- Bloom Syndrome: Children with this very rare condition are small at birth and rarely reach 5 feet in height as adults. They also have red, sun-sensitive facial skin; lesions; an increased susceptibility to respiratory tract and ear infections and a higher rate of certain cancers. The carrier rate is about one in 100 for Ashkenazic Jews.
- Canavan Disease: This disease affects children at about 2 to 4 months, at which time they begin losing previously attained skills. Most children die by the age of 5. Carrier rate: one in 40 Ashkenazic Jews.
- Cystic Fibrosis (CF): CF causes the body to produce a thick mucus that accumulates primarily in the lungs and digestive tract, resulting in chronic lung infections and poor growth. Carrier rate: one in 25 Caucasians, including Ashkenazic Jews.
- Familial Dysautonomia (FD): FD affects the regulation of body temperature, motor coordination, speech, blood pressure, stress response, swallowing, the ability to make tears and digestion. Carrier rate: one in 30 Ashkenazic Jews.
- Fanconi Anemia - Type C: Fanconi Anemia is associated with short stature, bone marrow failure and a predisposition to leukemia and other cancers. Some children may have learning difficulties or mental retardation. Carrier rate: one in 89 Ashkenazic Jews.
- Gaucher Disease - Type 1: This is the most common Jewish genetic disease, occurring in one out of every 1,000 Ashkenazic Jews. Symptoms usually begin in adulthood. Sufferers experience bone and joint pain, fractures and other orthopedic problems, anemia, easy bruising and poor blood clotting. This disease can now be treated safely and effectively with enzyme replacement therapy. Carrier rate: one in 12 Ashkenazic Jews.
- Mucolipidosis IV (ML IV): ML IV, one of the most recently recognized Jewish genetic diseases, is caused by the accumulation of harmful substances throughout the body. Individuals with ML IV experience a range of progressive motor and mental retardation, usually beginning at age 1. Early signs can include eye problems such as cornea clouding, crossed eyes and retinal degeneration. Individuals with ML IV currently are from one to 30 years old, and a prognosis beyond this age and life expectancy are not known. Carrier rate: unknown.
- Niemann-Pick Disease - Type A: Niemann-Pick is a neurodegenerative disorder in which a harmful amount of a fatty substance accumulates in different parts of the body. Symptoms include loss of brain function and enlargement of the liver and spleen. The average life expectancy of children with the disease is two to three years. Carrier rate: one in 90 Ashkenazic Jews.
- Tay-Sachs Disease (Infantile Type): Tay-Sachs disease is the most well-known Jewish genetic disease, potentially affecting one in every 2,500 Ashkenazic Jewish newborns. Children with Tay-Sachs disease develop normally until about 4 to 6 months of age when their central nervous system begins to degenerate because they lack an essential enzyme. The affected child loses all motor skills and becomes blind, deaf and unresponsive. Death usually occurs by age 4. Late-onset Tay-Sachs disease, which is more rare, has a slower and less severe progression of symptoms. Carrier rate: one in 25 Ashkenazic Jews.
Ideally, prospective parents should be tested prior to conception to determine if they are carriers. In most cases, at least one member of the couple will test negative, ruling out the possibility that their child will be born with any of these genetic diseases. If both test positive for the same disease, they should discuss their options with their obstetrician and a genetics counselor. Rabbinic counsel is also beneficial as couples consider the difficult choices that lie ahead. Many Orthodox communities encourage the use of premarital carrier screening to discourage the marriage of two carriers of the more devastating genetic diseases.
Sephardic Jews, whose ancestry can be traced to Spain, Portugal, North Africa and some Mediterranean regions, also suffer from certain genetic diseases. These include: beta-thalassemia, familial Mediterranean fever, glucose-6-phosphate dehydrogenase deficiency and Type III glycogen storage disease.
Although these genetic diseases are generally less devastating than those that affect Ashkenazic Jews, they can cause severe health problems and require proper treatment.
The gene for beta-thalassemia is carried by one in 30 individuals of Mediterranean descent, while one in five to seven North African and Iraqi Jews, Armenians and Turks carries the gene for familial Mediterranean fever. Type III glycogen storage disease, which is carried by one in 35 North African Jews, can only be inherited if both parents are carriers.
Unlike the other Sephardic genetic diseases, glucose 6-phosphate dehydrogenase deficiency, the most common human enzyme deficiency that affects an estimated 400 million people worldwide, is transmitted from a carrier mother to her male infant. Currently, there is no test to identify carriers.
Planning a family is a time of tremendous joy and excitement, and I greatly enjoy helping my patients as they move toward parenthood. As part of this process, I strongly encourage all Ashkenazic Jews to incorporate carrier testing for genetic diseases into their planning and for Sephardic Jews to discuss the need for testing with their physician. The testing only requires a simple blood test and it allows you to make informed family planning decisions.
Steven J. Wininger, M.D., a board-certified OB/GYN, practices at the Arizona Wellness Center for Women in Phoenix.
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