Fulminant multiple system atrophy in a young adult presenting as motor neuron disease.

A 34-year-old man demonstrated rapidly progressive motor neuron disease and, late in his 9-month clinical course, exhibited ophthalmoplegia and dysautonomic symptoms. Neuropathology showed spinal and bulbar motor neuron disease with severe involvement of extraocular motor nuclei, degeneration of spinal sympathetic and bulbar parasympathetic nuclei, striatonigral degeneration, and early olivopontocerebellar atrophy. This case underscores the diversity of multiple system atrophy and demonstrates an unusually rapid course in a young patient.