Choroideremia Symptoms

Choroideremia Symptoms

Choroideremia is characterized by extensive loss of all the layers in the eyes. Choroideremia usually begins during childhood with loss of the retina, the pigmented retinal epithelium (RPE) and choroid. The retina is a thin layer at the back of the eye composed of different types of light-sensitive nerve cells that detect light and give us colour vision and night vision. The RPE is a single layer of pigmented cells that lies on the outside of the retina. The choroid is the next layer and is also called the choroidea or choroid coat. It contains connective tissues and small blood vessels (vasculature) of the eye. It is the layer between the retina and the white part of the eye (the sclera).  The thickness of the human choroid layer varies, with the area right at the back of the eye being approximately twice as thick as that at the periphery. You can read in more detail about parts of the eye here: How Our Eyes Work

Night-blindness is often the first symptom of choroideremia, like many IRDs, and is usually first noticed in childhood. This can be followed by variable loss of side vision, known as the mid-periphery. These “blind spots” are initially experienced in an irregular circle, while central vision is still maintained. As time passes, the vision loss spreads around the whole periphery of the eye leading to “tunnel vision”. Central vision is usually maintained until late adulthood but, eventually, complete loss of sight occurs in late adulthood. The symptoms of choroideremia may vary greatly between affected individuals. Female carriers usually have very mild symptoms with night blindness or sensitivity to glare occurring late in life.

The symptoms of choroideremia can be very similar to several different disorders. This can lead to difficulties in determining which exact condition a person has. Differential diagnosis (the process of differentiating between two or more conditions which share similar signs or symptoms) can be useful. As choroideremia is a genetic or inherited condition with a known gene, a genetic diagnosis can determine a specific diagnosis of choroideremia and potentially exclude other conditions. Some of the other conditions that have similar symptoms include:

  • X linked retinitis pigmentosa (RP) – symptoms include poor night vision that progresses to loss of peripheral vision and tunnel vision. As it is X linked, it has a similar inheritance pattern to choroideremia

 

Gyrate atrophy of the choroid and retina – symptoms include vision loss due to circular loss of the choroid and retina. It can be diagnosed due to elevated blood levels of ornithine and people with this condition have other symptoms such as muscle weakness