Retinoblastoma and chromosome abnormality. Partial deletion of the long arm of chromosome 13.

A 7-year-old girl with retarded physical and mental development was found, on chromosome determination, to have deletion of a segment of the long arm of chromosome 13 (13 q—). A precise chromosome identification was made on peripheral leukocytes by using a quinacrine banding technique. Because of previous reports of an association of the 13 q—chromosomal abnormality with retinoblastoma, an ophthalmologic examination was carried out. The patient was found to have bilateral microphthalmia, and multifocal, moderately well-differentiated retinoblastoma in the left eye.