The case of a 38-year-old patient with rapidly progressing motor neuron disease, complicated by major dysfunction of the extrapyramidal system and of vertical gaze is described. Neuropathological examination revealed a degenerative process that severely affected the lower motor neurons, as well as the neurons of the pars compacta of the substantia nigra, the nucleus of Darkschewitsch, the nucleus interstitialis of Cajal, the colliculi superiores, and the pallidum. The long tracts were unaffected at all levels of the brain stem and spinal cord. There was no convincing evidence for the presence of a multiple system atrophy or progressive supranuclear palsy; the results rather revealed a pattern of vulnerability characteristic of a variant of motor neuron disease.