Retinoblastoma

Abstract

Retinoblastoma is the commonest intraocular tumour in children; even so it is excessively rare. It occurs either sporadically as a result of a spontaneous mutation or is inherited as a genetic mutation transmitted as an autosomal dominant characteristic. It is said to occur with the same frequency throughout the world, varying from 1 in 15000 [7] to 1 in 25000–30000 live births [6]. The incidence, however, is increasing because improved methods of treatment have resulted in more patients surviving to transmit the genetic defect to their offspring: in addition the spontaneous rate is also apparently increasing. François and Matton-Van Leuven [6] have laid down the following guidelines, which may be usefully applied in routine clinical practice: —

• 1. Healthy parents with one affected child do not run a high risk of producing more affected children (6%).

• 2. Patients with unilateral retinoblastoma should remain under medical control because the tumour can always become bilateral.

• 3. Brothers and sisters of a person with retino-blastoma should also be submitted to regular ophthalmoscopic examination.

• 4. Unilaterally affected offspring of retinoblastoma survivors run a high risk of developing the tumour bilaterally, even when the parent was affected unilaterally.

• 5. 5. When there are already two affected children in a sibship, further brothers and sisters run a serious risk of being affected, because one of the parents must be a carrier and at least 50% of the children risk being affected genetically.

• 6. 6. A retinoblastoma survivor who had a proven hereditary retinoblastoma has a 50% chance that some of his children will be affected.

• 7. 7. A sporadically affected survivor has a 25% chance that some of his children will be affected.

• 8. Apparently healthy persons who come from retinoblastoma families may carry the gene and pass the disease on to their offspring.