Familial idiopathic West syndrome

Two families, each with occurrence Of West syndrome in two siblings, are pr esented. Monozygotic twins in family 1 developed infantile spasms at the ag e of 4 months. Two female siblings in family 2 started to have seizures at the age of 6 months, but 2 years apart. The family history; development pri or to West syndrome; clinical, electroencephalographic, and neuro-radiologi c findings; diagnostic work-up; and treatment are described. The outcome in family 1 (follow-up after 2 years) showed no conspicuous findings on physi cal and neurologic examination, and psychomotor development appropriate to cognitive, motor, and language developmental age in both twins. Ln family 2 (follow-up after 3 and 5 years), the older sister only was one standard de viation below mean in intellectual developmental age. Simultaneous occurren ce of infantile spasms in both siblings from these two families but with va riable clinical expression suggests there is a genetic susceptibility and v ariable phenotypic expression. Long-term follow-up will demonstrate whether these cases may be classified as "familial idiopathic West syndrome.".