A T to C mutation in the polypyrimidine tract of the exon 9 splicing site of the RB1 gene responsible for low penetrance hereditary retinoblastoma

Four members of the family were affected; three had unilateral retinoblastoma (III.5, IV.12, and IV.13), diagnosed at 12, 12, and 24 months, respectively, and one had bilateral retinoblastoma (IV-6), which developed at 11 months. [...]with the exception of patient IV.13, the age of onset was not delayed compared to an average of less than 12 months in the majority of familial retinoblastoma. [...]these three mutations may also be the actual predisposing mutations in these families with low penetrance retinoblastoma.