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| OBSTETRICS
AND GYNECOLOGY Prenatal & Genetic Diagnostic Services |
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Carrier
Screening
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BACKGROUND |
Certain
genetic disorders are more common in one ethnic/racial group than another.
This information sheet describes some of these conditions. Each disorder
is described only briefly. If you would like more information about
a disorder or its treatment, please ask to be referred for genetic counseling.
All of these conditions are transmitted in autosomal recessive fashion. This means that a couple can only have a child with the disorder if both parents are “carriers” of the trait for that disorder. Carriers usually have no symptoms of the condition. Carrier tests are performed on blood samples. If both parents carry a trait for the same condition, during pregnancy their fetus can be tested for the disease by sampling the placenta or the amniotic fluid. Carrier tests cannot entirely eliminate the possibility of being a carrier, but a negative test makes the chance very low. If you are interested in carrier testing, call 773.702.6621 to make a genetic counseling appointment to discuss the most appropriate testing, the accuracy of test results, the laboratory that does the testing, and the cost. Check with your doctor first as you may have had carrier screening already. Some insurance companies do not cover the cost of testing. AFRICAN BACKGROUND Sickle cell disease (which includes SS disease, SC disease and S beta-thalassemia) occurs in 1:500 African-Americans. Children and adults with sickle cell disease have painful “crises” which may occur frequently or rarely. They are also at risk for poor growth and for childhood death due to infections. Strokes or kidney failure may occur at a young age. Carrier frequency is 1:12. Sickle Cell Anemia/NIH ASHKENAZI JEWISH BACKGROUND There are several conditions that are more common in the Ashkenazi Jewish population. If one member of the couple is Jewish and the other is not, the Jewish parent can be tested first. If he/she is positive for a trait, the non-Jewish parent can then be tested. For some of these conditions, testing a non-Jewish individual is less reliable. Tay-Sachs disease causes mental and physical deterioration of the child, with death usually by age 5. Carrier frequency is 1:30, and 1:3,600 Jewish children are affected. The Tay-Sachs gene is also more common among French Canadians from eastern Quebec and Cajuns from southern Louisiana. Canavan disease causes symptoms similar to Tay-Sachs. One in 40 Ashkenazi Jews carries this trait, and 1:6,400 children are affected. Canavan Disease/NIH Cystic Fibrosis (CF) - See description under Caucasian background. Niemann-Pick disease type A causes an enlarged liver and spleen, poor growth, and progressive physical and mental deterioration with death by age 4. The carrier rate is 1:90, and 1:32,000 Jewish children are affected. Fanconi anemia type C - Children have anemia, short stature, learning disabilities, or mental retardation. There may also be birth defects of the limbs, heart, or kidneys. Risk for leukemia and early death is increased. The carrier rate is 1:89 Jewish individuals, and 1:31,000 Jewish children are affected. Bloom syndrome results in poor growth and poor resistance to infection. There is a high rate of cancer from which individuals usually die before age 30. One in 100 Jewish individuals carries this trait, and 1:46,000 children are affected. Gaucher disease type 1 can be very mild or severe. Children and adults may have nosebleeds, anemia, an enlarged liver and spleen, bone pain, and easily broken bones. Because the severity is so variable, decisions about testing are difficult. The carrier frequency is 1:12, and 1:600 children are affected. CAUCASIAN BACKGROUND Cystic fibrosis (CF) is common among Caucasians, particularly those of Northern European origin. The disease causes lung infections, difficulty breathing, problems with bowel function, weight gain and growth. Children frequently need to be hospitalized, have physical therapy, and take several medications. The average lifespan is 30 years. One in 2,500 Caucasian newborns has cystic fibrosis, and 1:25 Caucasians carries the CF trait. Cystic Fibrosis/JAMA MEDITERRANEAN (GREEK, ITALIAN), SOUTHEAST ASIAN, AFRICAN BACKGROUND Beta-thalassemia is a disorder that causes severe anemia in children, requiring frequent blood transfusion. Children may grow poorly, have bone deformities or fractures, and develop heart failure from their disease. Carrier frequency varies with ethnic group. SOUTHEAST ASIAN BACKGROUND Alpha-thalassemia is a blood disease that results in severe anemia and, in some forms, death of the fetus or newborn. Carrier frequency varies but may be as high as 1:20. |
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| Copyright ©1998-2002
Dept. of Obstetrics and Gynecology, University of Chicago. All rights
reserved. Send questions and comments about this page to webmaster@babies.bsd.uchicago.edu. The information on this website is provided by the University of Chicago Hospitals & Health System for educational purposes only. It is not a substitute for professional medical care, and medical advice and services are not being offered. If you have, or suspect you a have, a health problem you should consult you physician. The University of Chicago Hospitals & Health System provides links to other organizations as a service to our readers; the Hospitals are not responsible for information provided in other websites. Please note: We do not answer on-line medical inquiries. |
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