Acquired focal choroidal excavation associated with multiple evanescent white dot syndrome: observations at onset and a pathogenic hypothesis

Background: The mechanism underlying focal choroidal excavation (FCE) remains largely unknown. We evaluated the sequential progression of FCE generation using enhanced depth imaging optical coherence tomography (EDI-OCT) in a patient with multiple evanescent white dot syndrome (MEWDS). Case presentation: A 37-year-old woman suffered MEWDS in the right eye. EDI-OCT showed the loss of photoreceptor inner segment/outer segment junction line, detachment between the retinal pigment epithelium (RPE) and Bruch's membrane, and dome-shaped, moderately reflective, focal photoreceptor-layer lesions corresponding to perifoveal white dots. The region with pigment epithelium detachment involved RPE/Bruch's membrane ruptures. After 1 month, almost all white dots spontaneously resolved together with improvements of the perifoveal OCT findings. Interestingly, perifoveal region developed a conforming-type FCE. An abnormal hyper-reflective lesion on OCT, regarded as fibrosis formation, simultaneously appeared within the choroid below the FCE and subsequently increased in size. Conclusions: These results suggest that the RPE/Bruch's membrane disruption due to chorioretinal abnormalities and subsequent intrachoroidal scar formation play a role in the pathogenesis on an acquired FCE.