Retinoblastoma – Genetic Counseling and Molecular Diagnosis

Retinoblastoma is a malignant embryonal tumour of childhood arising at the expense of retinal cones. It has an incidence of 1 per 15,000 to 20,000 births. In 90% of cases, it is diagnosed before the age of 3 years. The possibility of conservative management depends on early diagnosis (Moll et al., 1996). However, although treatment strategies have advanced considerably, the visual prognosis is still a major source of concern, especially central vision when the tumour is situated at or close to the macula. In two-thirds of cases, the lesion is unilateral and the median age of diagnosis is 2 years. In the other third, the lesion is bilateral and the disease is diagnosed earlier, possibly even during the neonatal period, with a median age of diagnosis of 1 year. Most cases of unilateral and bilateral retinoblastoma are sporadic, with no family history. However, 10 to 15% of all cases of retinoblastoma present a family history. The distribution of cases within the family is compatible with the existence of a tumour susceptibility gene transmitted according to an autosomal dominant mode with high penetrance. In this case, the lesion is usually bilateral and diagnosed at an early age.