The retina is the coating of the back of the eye made of specialized cells that process light and color for us to see. Uncontrolled growth of retinal cells due to a change in a gene, known as the retinoblastoma (RB) gene, causes retinoblastoma.
Retinoblastoma is a rare form of cancer, affecting 1 in 18,000 to 30,000 births. Retinoblastoma is considered a childhood cancer since 95% of cases occur in children under 5 years of age.
There seems to be an equal chance of the condition occurring in either eye, in either boys or girls, and regardless of race. About 75% of cases occur in one eye, and about 25% of cases occur in both eyes.
The body's cells reproduce themselves throughout a lifetime - tissues wear out and cells are replaced in a controlled manner. Retinoblastoma, like all cancers, occurs when that control is lost and cells begin to divide at an unusually high rate. Researchers are still working on the exact reasons for the gene mutation in retinoblastoma. However, they have discovered familial and non-familial causes for the disease.
Retinoblastomas can be classified into 2 categories: one caused by inheriting a defective gene (familial) and the other caused by a random change in the RB gene during cell replication (sporadic). The main cause of retinoblastoma is through the sporadic form. About 90% of children with retinoblastoma have no previous family history to the disease. Meanwhile, children with an affected parent only account for less than 10% of all diagnosed cases. Retinoblastoma that occurs in only one eye is usually not inherited. Retinoblastoma that occurs in both eyes is almost always inherited.
Although researchers are not completely sure of what causes the retinoblastoma gene to change and lead to retinoblastoma, they are aware of the risk factors for the condition.
Family history is the main risk factor for retinoblastoma. Children who inherit the altered gene have a 90% risk of developing retinoblastoma.
Smaller studies suggest that a parent infected with human papillomavirus (HPV) or a parent's type of job or work exposure may increase the risk of their offspring developing retinoblastoma, but these two observations are controversial within the medical community.