Hereditary Retinoblastoma

Hereditary retinoblastoma is a rather rare form of eye cancer that is passed to children when one parent has a specific gene mutation. This gene mutation will be present in all body cells, increasing the risk of cancer in other parts of the body and increasing the risk of recurring tumors. Having this gene mutation does not necessarily guarantee that the child will have retinoblastoma or cancer of any other body cells, however.

In the majority of cases of hereditary retinoblastoma, the cells of the eye manifest this mutation and tumors begin to form while the child is still in the womb or shortly afterward. Since the genetic mutation is present in both eyes, it is common for children that have hereditary retinoblastoma to have tumors in both eyes. This is called bilateral retinoblastoma. Cases of hereditary retinoblastoma represent about 40 percent of all cases of retinoblastoma.

Diagnosing Hereditary Retinoblastoma

If there is a family history of hereditary retinoblastoma, parents should request to have retinoblastoma testing done as early as possible. Children can now be tested for the genetic mutation that causes hereditary retinoblastoma while in the womb. If this genetic mutation is found, there is approximately a 90 percent chance that the child will be born with retinoblastoma, so physicians may induce birth early in order to begin treatment as soon as possible. Early treatment will ensure the highest likelihood of retaining vision and preserving quality of life.

Hereditary Retinoblastoma Genetic Mutation

In those that inherit the gene responsible for hereditary retinoblastoma, one of the two retinoblastoma genes that are normally present in each body cell is missing. Retinoblastoma genes, also called RB1 genes, create a protein that stops cells from dividing too quickly. This prevents tumors from forming.

Missing and Abnormal Genes

When a patient is missing this gene or the gene is abnormal, it leaves the cell vulnerable to mutations that will cause the cell to multiply at a fast pace. It is these excess cells that have been created by the malfunctioning cell that form a retinoblastoma tumor. Unfortunately, all body cells have this vulnerability in a person with hereditary retinoblastoma, and this is why the occurrence of secondary and recurring tumors is so common.

Hereditary vs. Non-hereditary Retinoblastoma

A patient that has non-hereditary retinoblastoma is missing both retinoblastoma genes in a retina cell. This creates the same pattern of destructive overproduction by the cell as hereditary retinoblastoma; however it is typically the only cell that bears this genetic mutation. For this reason, patients that have non-hereditary retinoblastoma typically do not develop second tumors, and the disease usually only affects one eye.

Odds of Inheritance

The chance of a non-hereditary retinoblastoma patient parenting a child with retinoblastoma is about four percent. The parents of a child with non-hereditary retinoblastoma have about a one percent chance of parenting a second child with the disease. Any children born from a parent with hereditary retinoblastoma have a 50 percent chance of inheriting the mutated gene that causes the disease.