Major gene is responsible for anencephaly among Iranian Jews.

Anencephaly is relatively frequent in Jews originating from Iran, in particular when its incidence is compared to that of open spina bifida in the same population (12 cases of anencephaly out of 14 cases of neural tube defects). The high incidence of this disorder in Iranian Jews, a relatively isolated community with a very high rate of consanguinity, suggests that anencephaly is caused by a major recessive gene. This possibility is supported by the sex ratio among these patients, which was significantly different from that observed for patients with anencephaly in other populations.