Retinoblastoma
Genetics
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Genes are working units of DNA, a complex pool of chemical information that carries a complete set of instructions to enable the cells of our body to function normally.
Retinoblastoma is due to the presence of errors or mutations in a single pair of genes (RB1 gene) in your child’s DNA. The RB1 gene normally acts to prevent or suppress tumour growth in the retinal cells lining the back of the eye.
The abnormal RB1 gene may be present in only a single cell in the retina or in every cell throughout the body. The genetic issues vary depending on whether your child presented with RB in one or both eyes and whether there was already a history of RB in the family:
Bilateral Sporadic Retinoblastoma
In children who are diagnosed with Bilateral Sporadic RB, mutation of the RB1 gene caused malfunction of this gene in every cell of the child’s body and so allowed for the growth of a number of retinoblastoma tumours in the retinal cells of either eye. Because of the presence of an abnormal gene in every cell of the body, these children are also at risk of tumours elsewhere in the body later in life.
Unless there is a history of RB in the parents or other members of the family, the chance of the child having inherited the condition from either parent is very small. Your eye doctor will look at the retina in both parents’ eyes to see whether either parent has evidence of RB that “died out” in childhood and was never discovered (spontaneously regressed retinoblastoma). Once again, the chance of this is very small, but unless genetic testing is carried out, the possibility of inheritance from one of the parents cannot be excluded. Because of this, all of the siblings (brothers and sisters) of a child with RB will have a small risk of inheriting the gene and developing the condition.
Later in life, children with Bilateral Sporadic RB will pass the abnormal gene to approximately half of their children, most of whom will develop RB.
Because of the risk of RB in both siblings and children of patients with RB, these newborn childrens’ eyes will need to be examined under a general anaesthetic (EUA) very soon after birth. Your eye doctor will recommend an EUA at two weeks of age and will need to perform regular EUAs until the age of four and a half or five years. Please follow the “Familial RB” link below for further information regarding follow up EUAs for siblings and children at risk of RB.
In recent years, accurate testing for the mutation in the RB1 gene that causes RB has become possible. Please press Genetic Testing for further information regarding testing of the RB1 gene.
Familial Retinoblastoma
In children with Familial RB (that is, one of their parents also had RB as a child), the abnormal RB1 gene has been passed down (inherited) from one of the parents. As in Bilateral Sporadic RB, malfunction of this gene in every cell of the child’s body allows for the potential growth of a number of retinoblastoma tumours in the retinal cells of either eye. These children are also at risk of tumours elsewhere in the body later in life.
Later in life, children with Familial RB will pass the abnormal gene to approximately half of their children, most of whom will develop RB.
Because of the risk of RB in children and siblings of patients with Familial RB, these newborn childrens’ eyes will need to be examined under a general anaesthetic (EUA) very soon after birth. Your eye doctor will recommend an EUA at two weeks of age and will need to perform regular EUAs until the age of four and a half or five years. Please follow the “Familial RB” link below for further information regarding follow up EUAs for siblings and children at risk of RB.
In recent years, accurate testing for the mutation in the RB1 gene that causes RB has become possible. Please press Genetic Testing for further information regarding testing of the RB1 gene.
Unilateral Sporadic Retinoblastoma
In most children who present with Unilateral Sporadic RB, mutation of the RB1 gene caused malfunction of this gene in only one of the child’s retinal cells and allowed only a single retinoblastoma tumour to form in the eye.
Most children with Unilateral Sporadic RB are not at risk of further tumours in either eye or elswhere in the body, and will not pass the condition on to their children.
Unless there is a history of RB in the parents or other members of the family, the chance of the child having inherited the condition from either parent is very small indeed. Your eye doctor will look at the retina in both parents’ eyes to see whether either parent has evidence of RB that “died out” in childhood and was never discovered (spontaneously regressed retinoblastoma). Once again, the chance of this is very small, but unless genetic testing is carried out, the possibility of inheritance from one of the parents cannot be excluded. Because of this, all of the siblings (brothers and sisters) of a child with RB will have a small risk of inheriting the gene and developing the condition.
Approximately 10% of children who present with Unilateral Sporadic RB have malfunction of the RB1 gene in every cell of their body, but do not have evidence of the condition in their healthy eye at the time of diagnosis. Later in life, these children will pass the abnormal gene to approximately half of their children, most of whom will develop RB. Without genetic testing, it is impossible to know which children with Unilateral Sporadic RB are at risk of passing the condition on to their children.
Because of the risk of RB in both siblings and children of patients with Unilateral Sporadic RB, these newborn childrens’ eyes will need to be examined under a general anaesthetic (EUA) very soon after birth. Your eye doctor will recommend an EUA at two weeks of age and will need to perform regular EUAs until the age of four and a half or five years. Please follow the “Familial RB” link below for further information regarding follow up EUAs for siblings and children at risk of RB.
In recent years, accurate testing for the mutation in the RB1 gene that causes RB has become possible. Please press Genetic Testing for further information regarding testing of the RB1 gene.