Congenital hypertrophy of the retinal pigment epithelium

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Congenital hypertrophy of the retinal pigment epithelium (CHRPE - 'chirpy') is a benign condition where the pigmentary lesions may be unilateral or bilateral, solitary or multifocal, with the latter sometimes being in the form of smaller patches that are grouped together, giving the impression of animal paw-prints (bear tracks) in the fundus.

Symptoms

There are no symptoms associated with CHRPE.

Signs

A typical CHRPE is flat and black or grey, with a sharply defined border, contrasting with the slate-grey, ill-defined appearance of a choroidal naevus. They can range from very small to many disc diameters in size. Frequently, a depigmented halo lies just inside the edge of the lesion. Further depigmented areas or lacunae may develop within the lesion with time. This is sometimes referred to as a sunburst effect. Some CHRPEs are conspicuously lacking in pigment, just having a pigmented edge. The multifocal, so-called bear-track form of CHRPE is often confined to a specific area within the fundus. CHRPE that are associated with FAP are described as atypical, being oval or even fishtail-like in shape, bilateral, more isolated in position rather than grouped together and variable in size up to approximately a disc diameter. CHRPE block choroidal fluorescence on fluorescein angiography.