13q interstitial deletion in a moroccan child with hereditary retinoblastoma and intellectual disability: A case report

Retinoblastoma is the most common malignant tumor of the eye in children (incidence:1/15,000 to 1/20,000 births), with a sex ratio of 1,5/1. Retinoblastoma, in its inherited form, is a disease caused by a syndrome of genetic predisposition to cancer. The RB1 gene, a tumor suppressor gene, is localized at 13q14. This case report shows the indication of the cytogenetic analysis in the management of patients with retinoblastoma, and the interest of a genetic counseling. We report the medical observation of a five and a half years old patient who was followed in the medical genetic's department for intellectual disability: associated with facial dysmorphia. The cytogenetic study objectified the presence of an interstitial deletion of the long arm of chromosome 13: 46, XX, del (13) (q14q22). A genetic counseling, with study of the karyotype of the parents is planned, specially to search for a balanced insertion: 13q14 insertion and deletion. In addition, the patient has been followed since the age of 9 months at the pediatric ophthalmology department for a bilateral retinoblastoma, in remission. A subject carry in constitutional mutation of the RB1 gene has a greater than 90% risk of developing retinoblastoma, and moreover has a genetic predisposition to secondary tumors. This medical observation shows the benefit of the constitutional cytogenetic study for patients with retinoblastoma, in particular in the event of bilateral retinoblastoma. The monitoring of psychomotor development must supplement the ophthalmological monitoring of these patients, with a systematic genetic counseling.