Prader-Willi syndrome. Variable severity and recurrence risk.

The families of 39 patients with Prader-Willi syndrome were examined for similarly affected individuals. The pertinent findings include (1) one sibling more profoundly affected than the patients usually described, (2) one first cousin more mildly affected than usual, (3) a suggestive history of increased frequency of spontaneous late miscarriage (17%) from the mothers of affected offspring, and (4) an occurrence rate of 1.6% in proband siblings.