High incidence of spinal muscular atrophy type I (Werdnig - Hoffmann disease) in the Karaite community in Israel.

Spinal muscular atrophy (S.M.A.) type I (Infantile werdnig - Hoffmann Disease) was found in 4:1,600 (1:400) infants of the Egyptian Karaite community. This group constitutes a representative sample of the Egyptian Karaite community in Israel, which numbers at present somewhat more than 7,000. The community existed as a religious and reproductive isolate for over 10 centuries. The very high gene frequency, 0.05 for the autosomal recessive gene of S.M.A. type I, is probably the result of genetic drift.