Acute Retinal Pigment Epitheliitis

ARPE, also known as Krill disease, is a rare, self-limited idiopathic unilateral or bilateral disease described in young adults (16 to 40 years) of both genders. Patients present with an acute drop in vision, typically no worse than 20/100, sometimes with metamorphopsia.

Examination reveals discrete clusters of round macular lesions at the level of the RPE composed of two to six pigmented spots reaching one-fourth disc diameter surrounded by a depigmented yellowish-white halo with no evidence of intraocular inflammation. Fluorescein angiography shows hypofluorescence corresponding to the pigmented center surrounded by a ring of hyperfluorescence. Electrophysiologic testing with ERG and visual evoked potential (VEP) tests are typically normal. The EOG, however, is subnormal and out of proportion to the changes observed in the retina. With resolution, the halo may disappear, leaving the pigmented central lesion. Over the course of 6 to 12 weeks, the vision and fundus spontaneously return to normal with the exception of subtle pigmentary changes.

The etiology of ARPE is unknown and laboratory testing is not useful for the diagnosis. Central serous retinopathy has been recognized in affected patients. The prognosis is good and no therapy is recommended. Recurrences are rare. A differential diagnosis may include adult-onset vitelliform foveomacular dystrophy, occult choroidal neovascularization, AMN, MEWDS, and APMPPE.