Retinitis pigmentosa - External and Internal Eye
The clinical picture may occur in isolation or as part of numerous syndromic conditions. These include abetalipoproteinemia, Usher syndrome, Biemond syndrome type 2, Jalili syndrome, Senior-Løken syndrome, Bardet-Biedl syndromes, disorders of glycosylation, Kearns-Sayre syndrome, gyrate atrophy, and neurodegeneration with brain iron accumulation (formerly Hallervorden-Spatz disease).
There is no known risk factor to RP. Many gene mutations are associated with it, the most common being the rhodopsin gene (RHO). RP can occur as a sporadic mutation or be autosomal dominant, recessive, or X-linked. Most autosomal recessive cases are associated with other systemic disorders. Patients can undergo genetic testing to see which gene mutations are associated with which disease. Mutation in RPE65 is particularly important as that mutation is the only one approved for genetic therapy.
True RP is a nonsyndromic ocular disease with a characteristic clinical picture as described here, while many of the pigmentary changes in the fundi of individuals with associated syndromes are more variable and should be called "pigmentary retinopathy" instead.
H35.52 – Pigmentary retinal dystrophy
28835009 – Retinitis pigmentosa
Differential Diagnosis & Pitfalls
Many retinal dystrophies can have similar pigmentary changes in the fundus, and further testing is necessary to distinguish these from the usual RP. Additionally, masquerade syndromes such as syphilitic retinopathy (see ocular syphilis) may mimic RP, and laboratory testing should include rapid plasma reagin (RPR) and venereal disease research laboratory (VDRL) tests or the fluorescent treponemal antibody absorption (FTA-ABS) test to rule out this disorder.
Many individuals complain of poor vision at night, but for most, there are physiological and environmental explanations and no disease is present. Persons who complain of photopsias (light flashes), defective color vision, or anomalies of central vision such as distortion usually have another retinal condition. An ophthalmologic evaluation with fundus examination and an ERG can rule out RP.
RP is a bilaterally symmetrical disease. When limited to one eye, the pigmentary changes are more likely due to environmental or nutritional defects. There are a few cases of asymmetric RP, however.