Aetiology of hydrops fetalis.

These 2 cases provide additional examples of HUS occurring in sibs after a long interval. The family resided in New York City, which is not considered as an endemic area for HUS, and the clinical course of the disease in both infants was almost identical, culminating in early death. The aetiology of HUS may indeed be multiple, and the genetic basis for a significant proportion of cases does not seem very likely. However, the familial cases with longer intervals between onset, as presented here, cannot simply be discarded as fortuitous instances of environmental causative factors. It may be that the genetic predisposition for HUS is operative in such families, implicating an autosomal recessive trait.