To report a case of ocular syphilis presenting as occult outer retinopathy.

A 42-year-old female presented with decreased visual acuity for one month in duration in the left eye. Her best-corrected visual acuity (BCVA) was 20/20 in the right eye and 20/250 in the left eye. There was no sign of inflammation in the anterior segment. Fundus examination showed no distinct abnormal findings including vitreous cell or haziness except mild diabetic retinopathy and subtle opacity of the macula. Spectral domain optical coherence tomography (OCT) showed a marked distortion of the inner segment-outer segment (IS-OS) junction in the photoreceptor layer without macular edema. Fluorescent angiography revealed diffuse subtle hyperfluorescence with microvasculitis in late phase. Full-field electroretinography (ERG) and multifocal ERG showed decreased amplitude; thus, acute zonal occult outer retinopathy (AZOOR) was considered as the diagnosis. Laboratory work-ups before steroid therapy revealed positive serology for active syphilis. One month after treatment with penicillin G (6 million international units per day for 14 days), best-corrected VA improved to 20/30, and restoration of the IS-OS junction was observed on OCT.

Ocular syphilis may present as occult outer retinopathy resembling AZOOR, and serologic work-up is required to avoid misdiagnosis. In the present case, anatomical and functional recovery were obtained after antibiotic therapy.