Contributor: Gordon K. Klintworth
The term pigmentary retinopathy refers to all retinal degenerative diseases characterized by the presence of melanin within the abnormal retina. It is a more precise term for what is commonly referred to by the misnomer retinitis pigmentosa. The latter term includes the word retinitis, which indicates inflammation of the retina, despite the fact that an inflammatory reaction is absent. The more accurate designation pigmentary retinopathy includes all non-inflammatory inherited retinal degenerations in which the rods and cones degenerate. Initial symptoms include nyctalopia during adolescence. A ring scotoma develops and extends peripherally until only a small visual field remains (tunnel vision, visual field constriction), which too is eventually lost. Fundoscopic examination reveals extremely attenuated retinal blood vessels. Eventually the ERG shows no activity. The optic disc develops a waxy yellowish pallor due to glial proliferation. The retinal pigment epithelium atrophies and becomes mottled gray with hyperpigmented and hypopigmented areas. The pigment has an appearance of bone corpuscles. The choriocapillaris eventually atrophies, exposing large vessels and a whitish yellow choroid.
Pigmentary retinopathy is a clinically and genetically heterogeneous group of retinal degenerations that primarily affect the rod photoreceptors. Initial symptoms include nyctalopia during adolescence. A ring scotoma develops and extends peripherally until only a small visual field remains (tunnel vision, visual field constriction), which too is eventually lost. Fundoscopic exam reveals extremely attenuated retinal blood vessels. Eventually the electroretinogram shows no activity. The optic disc develops a waxy yellowish pallor due to glial proliferation. The retinal pigment epithelium atrophies and becomes mottled gray with hyperpigmented and hypopigmented areas. The intraretinal pigment has been likened to bone spicules or the appearance of  bone corpuscles. The choriocapillaris eventually atrophies, exposing large vessels and a whitish yellow choroid.
Retinitis pigmentosa has many causes and numerous types are recognized. Based on the mode of inheritance retinitis pigmentosa can be divided into autosomal dominant [retinitis pigmentosa - autosomal dominant], autosomal recessive [retinitis pigmentosa - autosomal recessive] and X-linked [retinitis pigmentosa - X-linked] and Y-linked [retinitis pigmentosa - Y-linked] types.
At least 25 different loci for retinitis pigmentosa have been identified on different chromosomes. Genes causing retinitis pigmentosa have been mapped to chromosome 1 [retinitis pigmentosa type 12, retinitis pigmentosa type 18, retinitis pigmentosa type 19, retinitis pigmentosa type 20], chromosome 3, [retinitis pigmentosa type  4] chromosome 6 [retinitis pigmentosa type 7, retinitis pigmentosa type 14, retinitis pigmentosa type 25], chromosome 7 [retinitis pigmentosa type 9, retinitis pigmentosa type 10], chromosome 8 [retinitis pigmentosa type 1], chromosome 14 [retinitis pigmentosa type 16], chromosome 16 [retinitis pigmentosa type 22], chromosome 17 [ retinitis pigmentosa type 13, retinitis pigmentosa type 17], chromosome 19 [retinitis pigmentosa type 11, X-chromosome [retinitis pigmentosa type 2, retinitis pigmentosa type 3, retinitis pigmentosa type 6, retinitis pigmentosa type 15,  retinitis pigmentosa type 23,  retinitis pigmentosa type 24], Y chromosome and mitochondrial gene [retinitis pigmentosa type 8, retinitis pigmentosa type 21]. Retinitis pigmentosa type 5  no longer exists as it is probably the same as retinitis pigmentosa type 4. 
Mutations in numerous different genes cause retinitis pigmentosa. Some of genes encode members of the rod phototransduction cascade (rhodopsin, alpha and beta subunits of rod phosphodiesterase) and peripherin cause retinitis pigmentosa. One form of autosomal recesive retinitis pigmentosa maps to the region of the gamma-aminobutyric acid-receptor gene (including autosomal recessive retinitis pigmentosa).
Several ocular disorders have been reported in association with retinitis pigmentosa, but in most cases the significance of the association remains unknown. It many incidences it may be coincidental. Associations include keratoconus, myopia, posterior subcapsular cataract [cataract - posterior subcapsular], cystoid macular degeneration [macular degeneration - cystoid], and optic disk drusen [drusen - optic nerve] or hamartomas.
Mutations causing autosomal recessive retinitis pigmentosa have been found in the genes that encode numerous proteins (rhodopsin, a and b subunits of rod phosphodiesterase, in the a subunit of cyclic GMP gated-channel protein, RLBP1, ABCR, TULP1 and loci of autosomal recessive retinitis pigmentosa have been mapped to 1q31-q32.1 (RPE65), 2q31-33, 6q (RP25), and 16p12.1-p12.3. RHO, PDE6B, CNGC, PDE6A, 6cen-q15, CRALBP and 16p12.1-p12.3]. Cataract (especially posterior subcapsular cataract) [cataract - posterior subcapsular] is the most frequent anterior segment abnormality in retinitis pigmentosa. A pigmentary retinopathy is also a feature of lipodystrophy with congenital cataracts and neurodegeneration