AtypicalĬHRPE lesions associated with FAP are typically smaller in diameter (50-100 μm) than solitary lesions. Lesions tend to increase in size towards the fundus periphery lack haloes and lacunae and have been termed “bear tracks” due to their resemblance to animal footprints. Each cluster may include up to 30 lesions, which may vary from 100-300 μm in size, and are usually confined to one sector or quadrant of the fundus. Multiple lesions arranged in a cluster constitute grouped CHRPE. Used under a Creative Commons Attribution License.) Grouped (Multifocal) Ītypical pisiform CHRPE lesion with hypopigmented halo and smaller adjacent lesion. These hypopigmented areas show a tendency to enlarge slowly over time. The lesion may be surrounded by a marginal depigmented halo or contain multiple hypopigmented lacunae. Size varies from 100 μm to several disc diameters. Lesions are generally located equatorially, with a predominance in the superotemporal quadrant, but may be located throughout the fundus. There is typically a sharp demarcation between CHRPE and adjacent normal RPE, with a normal appearance of the overlying retina and vasculature. Color may vary from light gray to brown to black, with smooth or scalloped margins. Solitary CHRPE is typically a single, flat, round, hyperpigmented retinal lesion. Lesions are usually detected on dilated examination of the peripheral retina. Used under a Creative Commons Attribution License.) Physical examination Multiple CHRPE lesions arranged in grouped clusters, resembling animal footprints. A subset of patients may be known with FAP. The identification of multiple or bilateral lesions should alert the clinician to the possibility of underlying FAP.Īlmost exclusively asymptomatic. DiagnosisĬHRPE is usually an incidental finding made on routine ophthalmological examination.
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These lesions may be multi-layered or involve the full thickness of the retina. In comparison, atypical CHRPE lesions associated with FAP show RPE hypertrophy and hyperplasia, retinal invasion and retinal vascular changes. Glial cells replace the RPE and photoreceptor layer in areas of depigmented lacunae. 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%.
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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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