Multiple system atrophy.

Multiple system atrophy (MSA) is an adult-onset, progressive, neurodegenerative condition that has several different initial presentations. Ultimately affected patients develop parkinsonian features, autonomic dysfunction, cerebellar ataxia, and corticospinal deficits. Patients with MSA are often misdiagnosed as having Parkinson disease. This article discusses the epidemiology and pathophysiology of MSA, in addition to addressing clinical and diagnostic signs and symptoms, and the limited treatment options available to physicians.