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Retinoblastoma
Inheritance patterns and prenatal diagnosis
Inheritance patterns
There are two types of Retinoblastoma, a genetic or hereditary form and a non-genetic or non-hereditary form. Parents of children with Retinoblastoma should have their own eyes examined to check for signs of a spontaneously regressed tumour which has gone undetected. If this is present, then the parent carries the defective Retinoblastoma gene and all of their subsequent children have approximately a 1 in 2 chance of being affected. If the parents are unaffected, there is no family history of Retinoblastoma and the child is the first affected member of the family, then the chances of another child being affected are less than 1 in 20. All patients with bilateral tumours and approximately fifteen per cent of patients with unilateral tumours carry the defective Retinoblastoma gene and can pass the gene on to their children.
Prenatal diagnosis
Where there is a family history of Retinoblastoma, it is possible to carry out genetic studies of individual family members, to see who is carrying the defective gene and who is not. It is also possible to do the test during the early part of pregnancy, usually at about eleven weeks, or on the cord blood once the baby has been born. In most bilaterally affected individuals, it is possible to identify the genetic mutation and to offer pre- or post- natal screening for their offspring and other members of the family. It is now also possible to offer this service to some unilaterally affected individuals, particularly when surgery has been undertaken and where tumour tissue is available for analysis.
How is it treated?
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