Monday, March 21, 2011
Choroideremia is an inherited, retinal degenerative disorder that causes progressive loss of vision, affecting both the choroid and retina of the eye. Choroideremia leads to the degeneration of the choriocapillaris, the retinal pigment epithelium, and the retinal photoreceptor cells. Formerly called tapetochoroidal dystrophy, this condition occurs almost exclusively in males, in patients with a deletion of part of the X chromosome, including the region called Xq21. Such a deletion may cause choroideremia with severe mental retardation or with mental retardation and congenital deafness. In these individuals, the mothers are the carriers. In childhood, night blindness is the most common first symptom. As the disease progresses, there is loss of vision, frequently starting as an irregular ring that gradually expands both in toward central vision and out toward the extreme periphery. Progression of the disease continues throughout the individual's life. Both the rate of change and the degree of visual loss are variable among those affected, even within the same family.