I have just seen a patient with multiple pigment spots in her right eye only in the supero-temporal quadrant of the retina. The spots become bigger the further they are from the macula. What is going on?

This sounds very much like a case of congenital hypertrophy of the retinal pigment epithelium (CHRPE). This is a rare benign lesion of the retina, usually asymptomatic and detected at a routine eye examination. It results from a proliferation of pigmented epithelial cells and is well defined and flat. They do not cause visual symptoms if they do not reach the macula.

There are several different types and the classification is complex. This patient sounds as if they have the ‘grouped’ type. In some cases, there is only one isolated pigmented lesion, dark grey or black, with defined margins and located at the equator or in the peripheral retina.

Congenital retinal pigment epithelial hypertrophy is usually found before patients reach 30 years of age. They may enlarge with time but are not malignant. There are often referred to as ‘bear tracks’ because of their similarity to the tracks a bear would leave when walking.

The main problem with this grouped CHRPE is that the presence of more than three lesions is associated with familial adenomatous polyposis (FAP). This is an autosomal dominant condition characterized by adenomatous polyps throughout the rectum and colon, which usually start to develop in adolescence. The problem with FAP is that if untreated, virtually all patients will develop carcinoma of the colorectal region by the age of 50 years.

Photographic documentation of these lesions is recommended for future comparison. Ultrasonography and fluorescein angiography is typically used to differentiate RPE hypertrophy from uveal melanoma and certain rare intraocular tumours. Serial observation is warranted in that RPE hypertrophy can enlarge over time.

The patient deserves referral to an eye specialist that has access to these techniques. Referral to a gastrointestinal specialist is warranted if CHRPE is confirmed.