The X factor.

A 45-year-old white woman presented with chronic bilateral, painless, progressive, peripheral vision loss. She was found to have bilateral optic atrophy and nonenhancing multifocal white matter lesions on magnetic resonance imaging of the brain. Cerebrospinal fluid analysis showed an elevated level of myelin basic protein. She was diagnosed as having the carrier state of X-linked adrenoleukodystrophy. X-linked adrenoleukodystrophy can mimic the clinical and radiographic features of multiple sclerosis in a female carrier. To our knowledge, this is the first case report of bilateral optic atrophy in a female X-linked adrenoleukodystrophy carrier in the English ophthalmic literature.