Jewish Genetic Diseases
As researchers decode DNA, new findings and procedures bring hope to sufferers.
Reprinted with permission from Hadassah Magazine, January 2001 (82:5).
Twenty‑five years ago, the best Dr. Gideon Bach could offer patients was statistical probabilities. “I’d tell a couple who already had a sick child they had a one‑in‑four chance of having another,” says Dr. Bach, head of the Department of Human Genetics at the Hadassah‑Hebrew University Medical Center at Ein Karem. “It was difficult working with patients because we had so little to give them.” Today, tens of thousands of research hours later, geneticists the world over are heading toward a major payoff.
“We now know that most if not all human disorders have a genetic background, and we’re acquiring the tools to study, treat and eventually prevent or cure them,” says Dr. Bach, part of the team that recently identified the mutant gene responsible for mucolipidosis IV, a devastating disease carried largely by Ashkenazim (Jews of European origin). “Israel, with its many inbred ethnic groups, has proven a rich human laboratory for genetic detectives. It’s far easier to trace genetic anomalies in groups with homogenous pedigrees.”
Worldwide, more than 4,000 genetic diseases have been identified, most fortunately very rare. Almost all began with a mutation in the DNA which, because of inbreeding, was passed on rather than selected out. In Israel’s Arab population, in which consanguinity (blood relationship) is very high, every village, almost every family, carries its own disorders.
Jews are afflicted with their own particular disorders. Ashkenazim, who until some 40 years ago largely married within the group, carry a dozen recessive genetic anomalies in a relatively high frequency. The most widely known is Tay‑Sachs, a fatal neurodegenerative affliction that causes blindness, mental retardation and death, usually around age five.
One in 40 Ashkenazim carries the mutation that causes Canavan’s disease, which ravages its victims with failed mental development, weakened muscles and inability to speak, and victims usually die by age 10. About one in 100 Ashkenazim carry type A or B Niemann‑Pick disease, a crippling neurological disintegration that ends life well before the teens.
Familial dysautonomia, which leaves people unable to control their autonomic (involuntary) and sensory nervous systems, is carried by an estimated one in 30 Ashkenazim. One in 15 carries the mutation for Type 1 Gaucher, which is debilitating but not fatal. Mucolipidosis IV, cystic fibrosis, torsion dystonia, Fanconi anemia, Bloom syndrome and Von Gierke disease, all rare but utterly devastating, also appear more frequently among Ashkenazim than any other ethnic group.
The genetic disorders carried by Sephardim (Jews of Spanish and Middle Eastern origin) differ from those of the Ashkenazim, but the situation is generally far less clear‑cut.