RP is a hereditary disease that causes retinal degeneration. Several genes may cause RP, but mutations in the rhodopsin gene that code for an important G-protein coupled receptor in photoreceptor cells is implicated in the majority.
Night blindness, or nyctalopia, is due to the degeneration of rods. It can be assessed by measuring the time delay in dark adaptation or slow waves on electroretinogram.
As the degeneration of rods proceeds, contrast sensitivity decreases. Finer details like shadows and depth become more difficult to perceive. Colors also start appearing less distinct.
In late or advanced stages, peripheral retinal degeneration can result in peripheral visual field loss, or tunnel vision.
Abetalipoproteinemia is a malabsorption disease that results from mutations in the microsomal triglyceride transfer protein (MTTP) gene. It causes deficiencies of apolipoproteins B-48 and B-100.
Kearns-Sayre syndrome is classified as an inborn error of metabolism disease. It is a mitochondrial myopathy characterized by ophthalmoplegia, retinitis pigmentosa, and cardiac defects.
Refsum disease is a hereditary motor and sensory neuropathy. It is due to an accumulation of phytanic acid and can cause retinitis pigmentosa.
On fundoscopy, several bone spicule-shaped retinal deposits may be seen. They progress from the periphery to the macula.
Ultimately, this disease leads to permanent blindness as there is no cure.
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