Table 2. Proposed diagnostic framework for differentiating FAP-associated CHRPE from sporadic CHRPE and CGP.

Proposed stepwise approach to evaluating a pigmented RPE lesion for FAP association, progressing from clinical assessment to multimodal imaging.

CGP, congenital grouped pigmentation; CHRPE, congenital hypertrophy of the retinal pigment epithelium; FAP, familial adenomatous polyposis; PED, pigment epithelial detachment; RPE, retinal pigment epithelium.

Step	Assessment	Interpretation
Step 1	Number & laterality	Multiple lesions (sensitivity ~86.6%, specificity ~100%) and bilateral lesions (sensitivity ~84.3%, specificity ~100%) strongly suggest FAP [42]. A solitary unilateral lesion is most consistent with sporadic CHRPE. A unilateral sectorial cluster radiating from the optic disc suggests CGP [33].
Step 2	Fundoscopic morphology	Lacunae strongly favor sporadic CHRPE and argue against FAP [25,28]. A depigmented halo (48.5%) is common in FAP-associated lesions, with the majority containing a fish-tail pattern directed at the optic disc [28]. Nested falciform spots, or “bear tracks”, fitting into one another, are pathognomonic for CGP [33].
Step 3	Multimodal imaging	Absence of cystoid edema and presence of PEDs favor FAP-associated CHRPE [28]. Cystoid edema or subretinal clefts favor sporadic CHRPE [25]. Normal retinal lamination without outer-retinal atrophy distinguishes CGP from both CHRPE types [34].