Choroideremia is a rare inherited disorder that causes progressive loss of vision due to degeneration of the choroid and retina.
Choroideremia, formerly called tapetochoroidal dystrophy, occurs almost exclusively in males, due to its X-linked inheritance. In childhood, night blindness is the most common first symptom. As the disease progresses, there is loss of peripheral vision or "tunnel vision", and later a loss of central vision. Progression of the disease continues throughout the individual's life, although both the rate and the degree of visual loss can vary, even within the same family.
Vision loss due to choroideremia is caused by degeneration of several layers of cells that are essential to sight. These layers, which line the inside of the back of the eye, are called the choroids, the retinal pigment epithelium and the photoreceptors. The retinal pigment epithelium and the choroid initially deteriorate to cause choroideremia. Eventually, the photoreceptors break down as well. As the disease progresses, the clinical appearance of these cell layers changes in a characteristic manner and more vision is lost.
Choroideremia is genetically passed through families by the X-linked pattern of inheritance. In this type of inheritance, the gene for the disease is located on the X chromosome.