A 62-year-old man with fluctuating neurological deficits and skin lesions.

A 62-year-old man with no significant medical history experienced fatigue, night sweats, hoarseness of voice, and dry cough, which were followed by vision disturbances in his left eye. He lost about 4.5 kg (10 lb) in just over a month. Three weeks later, he had difficulty recollecting his e-mail password and trouble with word finding. The next day, he experienced numbness in his left arm. He also developed a maculopapular and erythematous rash in the groin, genitalia, and buttocks. The results of an initial neurological examination were normal, including his higher mental functions. An initial blood workup revealed normocytic normochromic anemia. The results of cerebrospinal fluid studies were unremarkable. Magnetic resonance imaging of his brain at hospital admission revealed multifocal increased T2 signals in the subcortical white matter. A conventional cerebral angiogram was unremarkable. A biopsy specimen from the right frontal lobe revealed demyelination and perivascular lymphocytic infiltration. A provisional diagnosis of acute disseminated encephalomyelitis was made. In spite of steroid treatment and plasmapheresis, his clinical status deteriorated rapidly. The approach to the diagnosis of a rapidly progressive multifocal brain disorder is discussed.