A rare case of a one-year-old child with Wilms' tumor, aniridia and glaucoma is described, in whom bone marrow chromosome analysis showed the presence of an interstitial microdeletion on the short arm of chromosome 11, presumably involving the p13 band. Research of the enzyme activity of RBC catalase showed a 40% reduction. This finding is compatible with the loss of the 11p13 band which contains the gene coding this enzyme. 11p13 deletion in Wilms' tumor and 13q interstitial deletion in retinoblastoma provide a rare case of prezygotic chromosome abnormality, which may be considered to have a determinant role in the tumor etiopathogenesis.
