Primary lateral sclerosis in a child.

Primary lateral sclerosis (PLS), previously undescribed in children, is characterized by a spastic motor deterioration and pathologic demonstration of corticospinal tract degeneration. We report an infant who, before 12 months of age, developed a progressive motor disease characterized by generalized spasticity. He died at 47 months, and neuropathologic examination revealed only corticospinal tract degeneration. We conclude that this child had typical clinical and pathologic findings for PLS.