A study of infantile motor neuron disease with neurofilament and ubiquitin immunocytochemistry.

We report a patient with infantile motor neuron disease who had pathologic findings consistent with multisystem degeneration. Although the muscle showed denervation atrophy and spinal anterior horn cells showed either atrophy or ballooning degeneration consistent with lower motor neuron disease, the infant was hypertonic and spastic. Degenerative changes were also detected in the dorsal root ganglia, cerebellum, and thalamus. Immunohistochemical studies showed a paucity of neurofilament (NF) staining in the corticospinal tract and accumulation of phosphorylated NF in ballooned neurons. Antibodies to ubiquitin immunostained ballooned neurons in the dorsal root ganglia, anterior horns, and thalamus. Accumulation of ubiquitinated and phosphorylated NF epitopes in degenerating neurons suggest that basic abnormalities in the neuronal cytoskeleton may be instrumental in the pathogenesis of this disorder.