The Ashkenazi Jewish Genetic Diseases Screen will screen for three genetic diseases. These include Tay Sachs disease, Canavan disease, and cystic fibrosis.
Tay Sachs disease is a progressive neurodegenerative disease that results from an enzyme deficiency. The symptoms first appear at about the age of six months when the baby begins to have neurological deterioration. This is a lethal condition and death usually occurs by five to eight years of age.
Canavan disease is a neurodegenerative disease clinically characterized by developmental delay, poor muscle control, and a large head. Canavan disease also results from a deficiency of an enzyme. Affected children with Canavan disease appear normal at birth but progressively deteriorate and die by their teenage years. There is no treatment or cure.
Cystic fibrosis (CF) is a genetic disease characterized by pulmonary and gastrointestinal abnormalities. CF has been described in virtually all ethnic groups examined but is more common in Caucasians. Although improved treatment has resulted in increased life expectancy for individuals with CF, there is still no cure for this disease.
INHERITANCE of Tay Sachs, Canavan, and CF
Tay Sachs disease, Canavan disease, and CF are autosomal recessive disorders. All our genes come in pairs; they determine individual traits, such as eye color. In order for a child to have one of these genetic conditions, both individuals contributing to the child's genetic makeup need to carry one copy of the affected gene and pass the gene on. In other words, if the child inherits two copies of the gene (one from each parent), the child would be affected. When both members of a couple are determined to be carriers, there is a 1 in 4, or 25% chance to have an affected child and a 3 in 4, or 75% chance to have a child unaffected with the genetic condition.
An individual who is a carrier of the affected gene DOES NOT have the condition and suffers no ill effects of the gene.
CARRIER SCREENING
All individuals who are interested in screening will attend a brief educational session (about 30 minutes) prior to blood being drawn. It is mandatory that you attend this session so that you will understand all aspects of screening and its limitations.
LIMITATIONS OF SCREENING
For Tay Sachs screening, biochemical analysis will be done. We will be screening for 3 common mutations found in the Ashkenazi Jewish population associated with Tay Sachs disease. This screening will detect 98% of the carriers for Tay Sachs.
DNA mutation analysis will be done for Canavan disease for the two common mutations found in the Ashkenazi Jewish population that account for 97% of the carriers for this condition.
DNA mutation analysis of the 31 most common mutations will be done for Cystic Fibrosis. This detects 97% of the carriers for this condition in the Ashkenazi Jewish population.
An individual whose carrier screening is negative for any of these disorders will have his or her risk of being a carrier significantly decreased, but not eliminated.
NOTIFICATION OF RESULTS
We will send the results to you (and to your physician upon request) as soon as they are available (approximately 2 weeks). If both members of a couple are determined to be carriers, further genetic counseling will be recommended to discuss prenatal diagnosis options.
