Retinitis pigmentosa: mutations in a receptor tyrosine kinase gene, MERTK

Retinitis pigmentosa (RP) is a heterogeneous genetic disorder of the eyes. RP is characterized by abnormalities of photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) leading to progressive loss of vision. It starts with the night blindness or defective dark adaptation in patients followed by constriction of the peripheral visual fields. Eventually, late in the course of the disease, the patients lose their central vision. The diagnosis of RP is made when a patient has rod dysfuntion as measured by dark adaptation or electroretinogram (ERG) monitoring, progressive loss in photoreceptor function and loss of peripheral vision with bilateral involvement. In the early stage of the disease, the fundus (the bottom of eyes), appears normal. As the disease progresses, the fundus shows arteriolar narrowing, fine dust-like intraretinal pigmentation, and loss of pigment from the RPE. The retina in a RP patient at an advance stage of the disease is characterized by the presence of intraretinal and preretinal clumps of black melanin pigments appearing like bone spicules, markedly attenuated retinal vessels, loss of RPE and paleness of the optic nerve (Pagon 1993)