STUDY OF GENETICS, EPIDEMIOLOGY, AND VITAMIN USAGE IN FAMILIAL SPINA-BIFIDA IN THE UNITED-STATES IN THE 1990S

We analyzed family structure, genetic patterns, epidemiology, and vita min usage in a series of families with multiple cases of spina bifida (familial SB). Among 6,491 individuals ascertained in 72 families with familial SB, we identified 180 patients-85 males and 95 females. The number of collateral cases on the maternal side (49 of 3,588), analyze d by category of kinship, were significantly higher than those on the paternal side (16 of 2,903) (p = 0.0002). Genomic imprinting or a part ial mitochondrial contribution are possible mechanisms for this matern al effect. The proportion of US-born SB families reporting some Irish ancestry (49%, 34 of 70) or some German ancestry (50%, 35 of 70) were significantly higher than those for the US population at large. in con trast, the proportion of families reporting some African-American ance stry (1%, 1 of 70) was significantly lower. The elevated proportions o f families with Irish and German ancestry, the high frequency of SB in Northern Ireland and in certain regions of Germany, the reduced propo rtion of families with African-American ancestry, and the lower preval ence of SB in African-Americans all suggest a genetic contribution to the etiology of the disorder. In our study, the proportion of mothers who used supplemental vitamins during the periconceptional period (29% , 47 of 163) was not significantly different from that in the US popul ation at large.