Bilateral vision loss responsive to corticosteroids.

A 48-year-old woman presented with painless bilateral vision loss that began in the left eye and responded to steroids, followed by vision loss in the right eye one day after completing her steroid taper. Diagnosis was complicated by a positive screening test for Leber hereditary optic neuropathy and a negative workup for demyelinating disease. Steroid-dependent optic neuropathies such as autoimmune optic neuropathy and chronic relapsing inflammatory optic neuropathy were considered in the differential. Seven months after initial presentation, the patient developed a new periventricular white matter lesion, lesions on her cervical and thoracic spinal cord, bilateral leg weakness, and sensory loss consistent with multiple sclerosis.