Interstitial deletion, del(4)(q33q35.1), in a mother and two children.

The inheritance of autosomal deletions from affected parents has only rarely been reported. We report an unbalanced interstitial deletion, del(4)(q33q35.1), in a mother and two male offspring. The mother and older sib are mentally retarded but have only mild dysmorphic features. The younger sib, at five months, is showing signs of developmental delay. All three patients show some abnormalities in common with cases that have terminal deletions of 4q with breakpoints at 4q33, but in general exhibit less severe abnormalities. The family illustrates the importance of detailed cytogenetic analysis of children with developmental delay who do not display major dysmorphic features.