Bilateral retinoblastoma: a dominantly inherited affection.

Ten survivors of sporadic bilateral retinoblastoma had 14 offspring, of whom eight were affected, seven of them in both eyes. Other reports from the literature raise the total of similar unselected cases to 19 survivors with a total of 39 offspring, of whom 17 were affected in both eyes and three in one eye.The high incidence of the bilateral affection in dominantly inherited retinoblastoma-as recorded in the literature-and in the offspring of survivors from sporadic bilateral retinoblastoma, as reported in the present study, establish all cases of bilateral retinoblastoma as a dominant disorder either in transmission or as a new mutation. This disorder, though fully or almost fully penetrant, is not always fully expressed. A small proportion, probably about 5 to 10% of all cases of the much more common sporadic unilateral affection, are in fact incompletely expressed germinal mutations for bilateral retinoblastoma. There is some evidence that histological appearances may distinguish these potentially transmissible unilateral tumours from the mass of unilateral retinoblastoma which have no genetic significance.