Piebaldism in a mentally retarded girl with rare deletion of the long arm of chromosome 4.

A 4-year-old mentally retarded girl had congenital depigmentations of ventrolateral parts of the chest, abdomen, and legs. She also showed dysmorphic features of the head, thorax, and extremities, a pigmented ring in both irises, and a hernia of the left obliquus muscle. Cytogenetic investigations revealed deletion of chromosome 4 for the long arm segment q12-q21. The typical depigmentations, reported in four other patients with a similar chromosomal deletion, correspond with those in the autosomal dominant piebald trait. Mutations in the Kit protooncogene (mapped to the chromosome (4q11-4q12 region) have been found in patients affected with this dominant disorder. Piebaldism in children with developmental delay and dysmorphic features should alert the physician to the possibility of a deletion of the long arm of chromosome 4.