Ashkenazic Inheritance

The typical victim reveals the disorder on the very first day of his life. This baby stares at the world with a fixed, forlorn expression; he is devoid of reflexes; he cannot coordinate sucking and swallowing. Later he may seem to cry--but without tears. He will never revel in the joys of candy; he cannot taste the difference between sweet and sour. When he burns himself, he may not even feel the pain. He is a victim of dysautonomia--an inherited malfunction of the nervous system.

At a geneticists' meeting in Bar Harbor, Me., this week, Johns Hopkins University's Dr. Victor McKusick will report that his research team has now traced 150 U.S. families with a total of probably 250 dysautonomic children. All but two families are of Ashkenazic (North European Jewish) extraction, from which more than 98% of American Jews are descended. In those two families, the mother does not know of any Jewish ancestors. In Israel, the forebears of 30 such children were all Ashkenazim rather than Sephardim (Mediterranean Jews). How did dysautonomia become an Ashkenazic malady?

Billion to One. In roughly 1000 A.D., speculates Geneticist McKusick, a Rhineland Jew was hit in the gonads by either a cosmic ray or a ray from radioactive rock such as granite. By a billion-to-one chance, the ray damaged one of the genes that govern biochemical development in the embryo's nervous system, leaving a defect that impairs many automatic functions and sensory perception. While the victim's fertility was unimpaired, reasons McKusick, half of his many descendants carried the defective gene with them during a 13th century Jewish migration to Eastern Europe, the area that became the Pale of Settlement by a series of Czarist ukases beginning in 1791.

The defective gene was only one of tens of thousands in each sex cell (sperm or ovum); it was recessive, meaning that whenever it was paired with a normal gene, its maleficent action was blocked. Even so, it spread so far and wide that it eventually appeared among Ashkenazic families that did not know they were related. Then a husband and wife, each bearing the gene, began to have dysautonomic children. On the average, one-fourth of the offspring of such marriages will have two normal genes (see diagram); two will be healthy but carry one abnormal gene, while the fourth will have defective genes--as well as the disease.

Tasteless Tipoff. Dysautonomia was not recognized as a separate disease entity until 1949, when Dr. Conrad M. Riley described several New York City victims and it was hard to distinguish from other inherited defects. Then, at New York University Medical Center, Dr. Joseph Dancis and Dr. Alfred Smith found that dysautonomia had one unique feature: its victims lacked taste buds in the front and, in most cases, in the back of the tongue as well. This defect in taste buds signals defects in other parts of the nervous system.

About one-fourth of all dysautonomic children die by age ten, Dr. McKusick reports. After that the death rate mounts steadily; the oldest patient on record is 36. The usual cause of death is the very problem that the infant encounters at first feeding: inhalation of food into the lungs, causing pneumonia, often coupled with heart failure. So far, the best palliative treatment for dysautonomia consists of using tranquilizers to help control the intense vomiting that characterizes the disorder. There is no cure.

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