CHRPE: The FAP Board Exam Clue
Learn the CHRPE findings that distinguish it from melanoma and identify the multifocal bilateral pattern linked to FAP.
Congenital hypertrophy of the retinal pigment epithelium is typically what type of lesion?
CHRPE in 30 Seconds
CHRPE, or congenital hypertrophy of the retinal pigment epithelium, is a benign RPE lesion that is usually flat and pigmented. For NBEO and OKAP, distinguish it from malignant mimics and recognize that multiple bilateral atypical CHRPE lesions can signal familial adenomatous polyposis.
What CHRPE Looks Like
- Appearance: flat, darkly pigmented and well-circumscribed RPE lesion. Exam relevance: flat contour supports CHRPE over melanoma.
- Lacunae: depigmented areas may develop within the lesion. Exam relevance: lacunae are a classic CHRPE finding.
- Halo: a hypopigmented halo may surround the lesion. Exam relevance: halo supports the characteristic fundus appearance.
- Size: lesions range from small to large and are typically stable. Exam relevance: stability favors a benign diagnosis.
- Location: usually unilateral and solitary. Multiple bilateral atypical lesions raise FAP concern. Exam relevance: laterality and number change the systemic implications.
- Fundus finding: no elevation and no subretinal fluid. Exam relevance: these findings argue against choroidal melanoma.
4 Facts Exams Always Ask
- CHRPE arises from the RPE and is a benign lesion requiring observation only.
- Multiple bilateral atypical CHRPE lesions, also called pigmented ocular fundus lesions, are strongly associated with familial adenomatous polyposis caused by an APC gene mutation. Solitary CHRPE is not associated with FAP.
- CHRPE is flat without subretinal fluid or orange pigment. Choroidal melanoma is typically elevated and may show subretinal fluid, orange lipofuscin pigment and a mushroom shape on B-scan.
- Isolated CHRPE requires observation only. No treatment is needed.
The Classic Trap
The major NBEO and OKAP trap is calling a solitary CHRPE a choroidal melanoma. CHRPE is flat, pigmented and may contain lacunae with a surrounding halo. Choroidal melanoma is elevated and may show subretinal fluid, orange pigment from lipofuscin and a mushroom shape on B-scan. A second trap is missing the FAP association when lesions are multiple and bilateral. Note that classic grouped pigmentation sometimes called bear tracks is not the same as the multiple bilateral atypical CHRPE lesions associated with FAP.
Clinical Pearl
Multiple bilateral atypical CHRPE lesions are a well-recognized ocular marker of familial adenomatous polyposis caused by an APC gene mutation. Recognition during fundus examination should prompt GI referral because affected patients are at high risk of colorectal cancer. This is the highest-yield clinical implication of CHRPE for board exams and clinical practice.
Checkpoint 1
Multifocal or bilateral congenital hypertrophy of the retinal pigment epithelium (CHRPE) with atypical 'bear track' or 'fish-tail' lesions should raise suspicion for which systemic syndrome?
Checkpoint 2
The Collaborative Ocular Melanoma Study (COMS) found which outcome regarding pre-enucleation radiotherapy for large choroidal melanoma?
An asymptomatic patient presents for a routine eye examination. Dilated fundus examination shows multiple flat, darkly pigmented lesions with surrounding halos in both eyes. There is no elevation and no subretinal fluid. What systemic association should you consider?
Which lesion is generally more likely to metastasize than a benign choroidal nevus?
Sources & Reviewer Info
References
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 4: Ophthalmic Pathology and Intraocular Tumors.
- Shields CL, Shields JA. Clinical Ocular Oncology.
- American Academy of Ophthalmology. EyeWiki: Congenital Hypertrophy of the Retinal Pigment Epithelium.
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