The choroid, choriocapillaris and inner retinal layers are unaffected. The underlying Bruch’s membrane may be thickened and the overlying photoreceptor layer degenerates with increasing age. Most solitary and grouped CHRPE lesions are characterized by a monocellular layer of hypertrophied RPE cells, densely packed with large, round macromelanosomes. The phenotypic expression of CHRPE in FAP is regularly present with mutations between codons 446-1338 of the APC gene, but absent with mutations between codons 1445-1578. The severity of disease and presence of extracolonic features are associated with the location of the APC mutation. The gene encodes a tumor suppressor protein and is located on the long arm of chromosome 5 (5q21-q22). Mutations in the adenomatous polyposis coli (APC) gene are responsible for FAP. Used under a Creative Commons Attribution License.) Large, hyperpigmented solitary CHRPE lesion with hypopigmented partial halo and lacunae. Risk FactorsĪtypical CHRPE is the earliest and most common extra-colonic manifestation of FAP, present in up to 90% of patients. The prevalence of CHRPE in the general optometric population has been estimated to be 1.2%. FAP sub-types, including Gardner syndrome (FAP plus skeletal hamartomas and various soft tissue tumors) and Turcot syndrome (FAP plus various brain tumors) are also associated with atypical CHRPE. Left untreated, virtually all FAP patients develop colorectal carcinoma/s by middle age. Atypical CHRPE is associated with familial adenomatous polyposis (FAP), an autosomal dominant cancer syndrome, characterized by numerous adenomatous polyps of the colon and rectum. It is a congenital hamartoma of the retinal pigment epithelium (RPE) and occurs in three variant forms: solitary (unifocal), grouped (multifocal) and atypical. ICD-10: Q14.1 - congenital malformation of the retina.Ĭongenital hypertrophy of the retinal pigment epithelium (CHRPE) is a typically benign, asymptomatic, pigmented fundus lesion.
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