Page 1 of 1: RETINITIS PIGMENTOSA

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Retinitis pigmentosa, or RP, is a genetic eye condition. Progression of RP is different in each case. RP is a group of inherited disorders in which abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina lead to progressive visual loss. Affected individuals first experience defective dark adaptation or nyctalopia (night blindness), followed by constriction of the peripheral visual field and, eventually, loss of central vision late in the course of the disease.

SIGNS
Mottling of the retinal pigment epithelium with bone-spicule pigmentation is typically pathognomonic for retinis pigmentosa. Other ocular features include waxy pallor of the optic nerve head, attenuated retinal vessels, cellophane maculopathy, cystic macular edema, and posterior subcapsular cataract.

GENETICS
In 1989, a mutation of Rhodopsin, gene that plays an essential part in the visual transduction cascade, has been identified. Until now, more than 100 mutations have been found in this gene, accounting for 15% of all types of retinal degeneration. Most of those mutations are missense mutation and inherited mostly in a dominant manner.
At least 35 different genes or loci are known to cause nonsyndromic RP. DNA testing is available on a clinical basis for RLBP1 (autosomal recessive, Bothnia type RP), RP1 (autosomal dominant, RP1), RHO (autosomal dominant, RP4), RDS (autosomal dominant, RP7), PRPF8 (autosomal dominant, RP13), PRPF3 (autosomal dominant, RP18), CRB1 (autosomal recessive, RP12), ABCA4 (autosomal recessive, RP19), and RPE65 (autosomal recessive, RP20).

INHERITANCE
RP can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. X-linked RP can be either recessive, affecting primarily only males, or dominant, affecting both males and females, although females are always more mildly affected. Some digenic and mitochondrial forms have also been described.

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ASSOCIATED SYNDROMES

BASSEN-KORNZWEIG SYNDROME (ABETALIPOPROTEINEMIA): autosomal recessive. Jejunal biopsy is diagnosti
-RP
-ataxia
-acanthocytosis
-fat malabsorption

REFSUM'S SYNDROME: autosomal recessive, defective Phytanic acid metabolism
-RP
-peripheral neuropathy
-cerebellar ataxia
-elevated CSF proteins
-deafness
-icthyosis
-cardiac arrythmias

USHER'S SYNDROME: autosomal recessive
-RP
-sensorineural deafness

KEARNS-SAYRE SYNDROME:
-RP
-heart block
-progressive external ophthalmoplegia

LAURENCE-MOON-BIEDL SYNDROME: autosomal recessive
-RP
-mental retardation
-polydactyly
-obesity
-hypogonadism

COCKAYNE'S SYNDROME: autosomal recessive
-RP
-dwarfism
-bird-like facies
-flexion contracture of limbs
-mental retardation
-ataxia
-premature aging

FRIEDRICH'S ATAXIA:
-RP
-ataxia
-nystagmus

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Hallgren's syndrome:

-retinitis pigmentosa
-vestibulo-cerebellar ataxia
-congenital deafness
-mental deficiency

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