13q deletion syndrome and retinoblastoma in identical dichorionic diamniotic monozygotic twins.

Purpose: To report the case of identical dichorionic diamniotic female twins with unilateral retinoblastoma in 13q deletion syndrome.
Methods: Clinical and ophthalmoscopic evaluation, combination of multiple ligation-dependent probe amplification, array-comparative genomic hybridization analyses, and magnetic resonance imaging were performed.
Results: Peculiar facial features, marked hypotonia, gastroesophageal reflux, interatrial septal defect with left to right shunt and light dilatation of right chambers, 5th finger hypoplasia, 3rd-5th toes clinodactyly, 2nd toe overlapped to 3rd toe, and cutis marmorata were found. Ophthalmoscopic evaluation revealed unilateral retinoblastoma in both girls. Magnetic resonance imaging detected corpus callosum hypoplasia in both twins. A 34.4-Mb deletion involving bands 13q13.2-q21.33 and including the RB1 gene was identified in both twins. The deletion was not present in the DNA of their parents and older brother.
Conclusions: Dysmorphic features in children must be always suspicious of 13q deletion syndrome and a short ophthalmoscopic follow-up is necessary to detect the presence of a retinoblastoma.