Genetic study of infantile spasm with hypsarrhythmia.

Infantile spasms (IS) appear to be a distinct syndrome complicated by heterogeneous etiology. Family data support a multifactorial model involving a polygenic determination of susceptibility to IS but requiring environmental factors such as anoxia, birth trauma, or immunization to precipitate seizures. The empiric recurrence risk among siblings was estimated to be 15 +/- 3 and for all first degree relatives as 7 +/- 5 per 1,000. These risks should be interpreted with caution since possible heterogeneity of IS may result in the occurrence of families in which cases are presumably totally environmental, and other rare families which may be segregating for an autosomal recessive disorder. Careful review of involved medical and family histories and a thorough physical examination should permit discrimination among these possibilities.