A genetic study of retinoblastoma.

Eight patients with retinoblastoma (RB) were studied by high resolution chromosome R-banding technique, and the esterase D was quantitatively determined in red blood cells of the patients. Among these patients, 2 showed 13q14 deletion mosaicism, 1 showed a monosomy 13q14.1-q14.2, and the remaining 5 had normal karyotype. Our findings indicated that 1) the RB gene is located at 13q14.1. The result confirmed previous data; 2) 13q deletion is an important event in the development of RB; and 3) esterase D determination is an important diagnostic tool in the detection of 13q deletion, useful for prenatal diagnosis and genetic counselling.