Aniridia, cataracts, and Wilms' tumor in monozygous twins.

We studied the first instance of aniridia-Wilms' tumor syndrome in twins who were mentally retarded. Both of them had congenital aniridia, cataracts, and glaucoma; only one subsequently developed a Wilms' tumor. A two-allele, two-step mutation is the most likely explanation of this genetically abnormal syndrome in twins. The aniridia-Wilms' tumor syndrome in twins further documents the relationship of teratogenic malformations and neoplasias.