Cytogenetic and molecular investigation of a balanced Xq13q translocation in a patient with retinoblastoma.

We report on a 4-year-old girl with retinoblastoma and de novo balanced translocation [46,X,t (X;13) (q23;q13)]. Unilateral retinoblastoma was discovered at age 9 months along with developmental delay and several manifestations of Turner syndrome. Chromosome studies showed an X/13 translocation and an X inactivation pattern showing the translocated X chromosome active in all 50 cells examined. Standard Southern blot analysis and pulsed field gel electrophoresis using a 3.8 kb EcoR1 fragment of the cDNA probe to the 3' end of the RB1 locus demonstrated a normal genomic pattern. The results of the cytogenetic and molecular analysis suggests that the RB1 locus has not been disrupted by the chromosome rearrangement. This case is the fifth report of an X/13 translocation associated with a retinoblastoma.