Author response: pachychoroid pigment epitheliopathy may masquerade as acute retinal pigment epitheliitis.

We appreciate the interest of Pang and Freund in our recently published manuscript, ‘‘Acute Retinal Pigment Epitheliitis: Spectral-Domain Optical Coherence Tomography Finding in 18 Cases.’’ Because of similarities in the clinical features of acute retinal pigment epitheliitis and pachychoroid pigment epitheliopathy, they have questioned that ‘‘pachychoroid (pachy-[prefix]:thick) pigment epithliopathy’’ might masquerade as acute retinal pigment epitheliitis. It has been reported that pachychoroid pigment epitheliopathy could be a ‘‘forme fruste’’ of central serous chorioretinopathy (CSC). However, there was no evidence of CSC in our acute retinal pigment epitheliitis patients until now, and there were several differences in clinical features between CSC and pachychoroid pigment epitheliopathy. First, there were no CSC risk factors in our patients; the patients had no history of corticosteroid use or Type A personality characteristics. In addition, no patients had previous CSC history or showed any subretinal fluid collection during the follow-up periods, even in the contralateral eye. Second, the clinical findings of retinal pigment epitheliitis (RPE) abnormalities in our patients were similar, but not identical to those observed in pachychoroid pigment epitheliopathy, as previously stated. The pigmented lesions of the macula in our article were all limited to the fovea or foveolar area, and all lesions were solitary. There were no juxtafoveal or extrafoveal pigmented lesions and no other adjacent granular pigmented lesions around the macula. In addition, the optical coherence tomography (OCT) findings in our patients showed no pigment epithelium detachment (PED) or PED-like lesions, and only showed minute changes that decreased reflectivity and/or disruption of the inner RPE and inner segment ellipsoid. The most important finding of pachychoroid pigment epitheliopathy is the thickened choroid and/or dilated choroidal vessels. To the best of our knowledge, there have been no reports on the association between a thickened choroid and acute retinal pigment epitheliitis. We have tried to identify the choroidal thickness in patients with acute retinal pigment epitheliitis through re-review of the medical records of our patients in the article; however, unfortunately, spectral domain (SD) OCT images with enhanced depth imaging (EDI) were available only for two patients among all the participants. These patients’ subfoveal choroidal thickness (vertical distance from the hyperreflective line of the Bruch’s membrane to the hyperreflective line of the inner surface of the sclera on fovea-centered SD-OCT image) values were 226 and 283 lm. Moreover, they showed no dilated choroidal vessels associated with lesions of the outer retina on OCT. The two patients showed no thickened subfoveal choroid; however, it still is possible that patients with thickened choroids would be included in our acute retinal pigment epitheliitis patient population, considering the limited choroidal thickness data. We failed to find an association between the characteristics of the choroid and acute retinal pigment epitheliopathy due to our data limitations. The characteristics of the choroid in acute retinal pigment epitheliitis should be investigated in the future. We agree that using OCT findings of the outer retina to make a differential diagnosis between pachychoroid pigment epitheliopathy and acute retinal pigment epitheliitis can be difficult. As Pang and Freund stated, distinguishing between the diseases might be important since pachychoroid pigment epitheliopathy can potentially develop into CSC or polypoidal choroidal vasculopathy. Choroidal thickness measurements or analysis of choroidal morphology can be helpful to differentiate between the two rare diseases. Further investigation is warranted for these unique macular diseases.