The retina of the eye has many cell types, among them the rods and cones that respond to light and transmit them to the brain. The many biochemical reactions in the rods and cones are under gene control and mutations in these are responsible for a large number of hereditary eye disorders. Among these are a group of conditions called retinitis pigmentosa which resemble each other clinically so closely that gene studies are necessary to distinguish them.
Difficulties with dim or night vision are apparent in early childhood. Vision loss is evident soon thereafter. Infants often stare at lights and eye-rubbing is noted somewhat later. Characteristic changes of retinitis pigmentosa can be noted by ophthalmologists during early childhood. The loss of vision is progressive and in adulthood is often limited to light perception. To-and-from eye movements (nystagmus) has been reported in some patients. A test known as an ERG (electroretinogram) is abnormal early in life and is diagnostic for retinitis pigmentosa of all types.
The full extent of abnormalities outside the eye remains to be determined. A mild developmental delay has been reported in some patients but it is doubtful that the majority of individuals have been tested. X-ray changes in the fingers also been noted along with shortened digits in those who had radiographic studies but other authors have not mentioned this feature. At least one individual had early childhood hearing loss but the majority of patients have not been tested.
There us no known impact on longevity.
This is an autosomal recessive disorder in which changes (mutations) in both copies of a specific gene have been found. The parents are clinically normal but carry a single copy of this change. When both carry this single copy their children each have a 25% chance of inheriting two copies.
Because of the clinical similarities of the many types of retinitis pigmentosa, gene testing is necessary to make the exact diagnosis.
Since there are no outward physical signs, the diagnosis is usually not made at birth. However, if other relatives have retinitis pigmentosa (siblings in particular), an ERG should be done which can enable the diagnosis to be made even in the first years of life. If the ERG is abnormal, neurocognitive testing and X-ray studies should be done later in the first decade.