Retinoblastomas may occur in one or both eyes, and may be heritable or non-heritable in their pattern. They typically occur in children less than 5 years of age.
A retinoblastoma is a malignant tumor of the retina, the light-sensitive layer of tissue at the back of the eye. It arises in response to one of hundreds of mutations in the RB1 gene which is a tumor suppressor gene. It regulates the cell cycle functions which are responsible for controlled and directed cell proliferation, as well as cell differentiation and cell survival.
The presence of mutations in both copies of the gene, or their absence, causes cancerous changes in retinal cells, which lead to the formation of one or more retinoblastomas.
Signs of a Retinoblastoma
The most prominent and common sign of a retinoblastoma is the absence of the normal red reflex that occurs when a light is shone into the child’s eyes. This reddish color results from the reflection of light from the rich network of retinal blood vessels. In a child with retinoblastoma, instead of red, the pupil looks white in the reflection. This is called leukocoria, and is often first detected when a flash is used to take a photo of the child, and the result shows white pupils instead of red. If the room is darkened, a flashlight shone into the child’s eyes picks up the same result. The pupil may be partly or completely white. This sign is seen in 6 of every 10 patients with retinoblastoma.
The appearance of a squint is another way in which this condition shows up first. Both eyes should be the same size, and move together when the child looks at an object. With the child focusing on something, the line of sight from each eye should not cross with that of the other. It can be tested, in cases of doubt, by covering each eye in turn with the child looking at something. The exposed eye should maintain the original position even when the other eye is covered. The presence of a squint, or strabismus, is found in 20% of children with retinoblastoma.
In 10% of cases, the child may have pseudoinflammation of the affected eye, manifesting as pain or redness of the eye that persists for a long time.
Other Less Common Symptoms
- The eyeball may look enlarged or bulge forward, which is called proptosis.
- The iris and pupil may have a cloudy appearance.
- Both irises may be of different colors, a phenomenon called heterochromia.
- The pupil may appear distorted, or be smaller than the other pupil.
- The child may have double vision.
- Cataracts may be present.
- The child may present with nystagmus, or jerky oscillations of the eyeballs.
Systemic symptoms associated with retinoblastomas include bone pain due to metastasis or concurrent osteosarcomas.
These individuals need to be monitored for life, as up to half of patients with the inherited form and 5% of those with the sporadic mutation will develop a second cancer within the next 5 decades.