During a routine blood test, a teenager was found to be homozygous recessive (i.e., possessed both recessive genes) for adult onset Tay Sachs disease. Unlike the more commonly known form of the disease, which becomes apparent at a very young age, this form first appears in the late teens or early twenties. The symptoms associated with a mild case may include minor body tremors, weakness in the legs or mild memory deficits. In more severe cases, symptoms may progress to the weakening of all limbs, paraplegia, severe memory loss and psychosis. Adult onset Tay Sachs disease can be fatal.
Only approximately 100 cases have been identified worldwide and there is litle useful medical experience concerning the progress of the disease. There is no known cure.
So far, only the teenager's parents and atttending physician are aware of the test results.
Should anyone else be informed of this genetic situation? If the answr is yes, when would be an appropriate time? Should the teenager's siblings be genetically tested? What, if any, are the practical implications of testing?
The diagnosed teenager should not be informed until he begins to meet marriage prospects. When this occurs, both he and his possible bride should be informed of his diagnosis before any emotional bond develops between them.
The other siblings have a one in four genetic chance of also being afflicted by this homozygous condition. They should not be informed until they also begin to meet marriage prospects. At that time, each sibling should be genetically tested. If the results indicate the homozygous recessive condition, then each sibling and the possible marriage partner should be informed before an emotional bond develops.
This case study should not be applied as a general rule. Instead, cases should be ruled upon individually by a competent halachic authority.