Retinoblastoma and Subband Deletion of Chromosome 13

Two patients with retinoblastoma and an interstitial deletion of the long arm of chromosome 13 were studied using G-banded metaphase and prophase chromosomes. One patient showed several congenital defects, developmental retardation, and deletion of bands q14 and q21. The second patient showed mild developmental delay, a few minor congenital defects, and a loss of approximately half of band q14. On the basis of this study and nine others from the literature, it is now possible to tentatively assign a predisposition to retinoblastoma to deletion of a specific small region of chromosome 13.