[From gene to disease; retinoblastoma and the RB1 gene]

Retinoblastoma is caused by mutations in the RB1 gene. The penetrance is 95%, as in approximately 5% of the mutation carriers, no second somatic mutation occurs in one of their retina cells during embryonic development. Molecular diagnosis is performed by a complete scanning of the RB1 coding sequence which includes flanking intronic sequences. Approximately 85% of pathogenic mutations can be identified.