An eye examination can reveal findings that point to health issues in other parts of the body. One such finding is Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE), a condition involving a cell layer in the back of the eye. While often pigmented, a rarer form exists that lacks coloration, known as amelanotic CHRPE. The term “amelanotic” signifies the absence of melanin, the pigment responsible for color in skin, hair, and eyes.
Defining Amelanotic CHRPE
Amelanotic CHRPE is a benign and congenital hamartoma, a non-cancerous, disorganized growth of cells native to the area in which it is found. These lesions are located in the retinal pigment epithelium (RPE), a single layer of cells at the back of the eye. The RPE has several functions, including absorbing light and nourishing the retina’s photoreceptor cells, which are responsible for vision.
The absence of pigment gives the lesion a pale, translucent, or sometimes reddish-orange appearance. Histologically, the cells in a CHRPE lesion are larger and more disorganized than the surrounding normal RPE cells, but they do not invade other tissues or spread. Because it is congenital, amelanotic CHRPE is present at birth, though it is often not discovered until later in life.
Identifying Amelanotic CHRPE
Amelanotic CHRPE is almost always asymptomatic, meaning it does not cause vision loss or other noticeable symptoms. Consequently, it is discovered by chance during a routine dilated fundus examination performed by an optometrist or ophthalmologist. When viewed, an amelanotic CHRPE lesion appears as a flat, well-demarcated area that is pale or translucent with smooth or slightly scalloped borders.
For a more detailed view, an eye doctor might use advanced imaging techniques. Fundus autofluorescence (FAF) is a non-invasive imaging method that can highlight the lesion, which typically shows hypoautofluorescence. Another tool is Optical Coherence Tomography (OCT), which provides a cross-sectional, high-resolution image of the retina. An OCT scan can confirm the lesion is located within the RPE layer, show thinning of the overlying photoreceptor cell layer, and verify that the lesion is flat, helping to distinguish it from other conditions such as a choroidal melanoma.
The Connection to Systemic Health
The presence of multiple, bilateral (in both eyes), and atypically shaped CHRPE lesions is strongly associated with a genetic condition called Familial Adenomatous Polyposis (FAP). FAP is an inherited disorder that causes the development of hundreds to thousands of polyps in the colon and rectum. If left untreated, these polyps have a nearly 100% chance of developing into colorectal cancer. Gardner Syndrome is a variant of FAP that includes the colonic polyps along with other non-cancerous tumors, such as osteomas and various skin growths.
The eye lesions associated with FAP are often the earliest detectable sign of the syndrome, appearing long before any intestinal symptoms arise. While the link is strongest with pigmented, atypical CHRPE, any finding of multiple lesions warrants further investigation. Four or more CHRPE lesions are considered highly suggestive of FAP.
An ophthalmologist who identifies these lesions will inquire about personal and family history of colon polyps or cancer and recommend a consultation with a gastroenterologist for a colonoscopy. The genetic basis for FAP is a mutation in the adenomatous polyposis coli (APC) gene, and genetic testing may also be recommended for the patient and their family members.
Clinical Management and Outlook
Once a diagnosis of amelanotic CHRPE is confirmed, the management approach depends on whether it is an isolated finding or associated with a systemic condition. For the eye lesion itself, the outlook is excellent. Isolated, solitary CHRPE lesions are considered benign, are not progressive, and rarely cause any vision problems, so they do not require treatment. An ophthalmologist will recommend periodic monitoring with follow-up examinations and fundus photography every one to two years to ensure it remains stable. Although exceedingly rare, nodular growths can develop from CHRPE, so long-term observation is a standard precaution.
If the presence of multiple or atypical CHRPE lesions leads to a diagnosis of FAP or Gardner Syndrome, the focus of management shifts entirely to the systemic condition. The management of FAP is intensive and may involve regular colonoscopies and, in many cases, preventative surgery to remove the colon.