Atypical infantile spinomuscular atrophy presenting as acute diaphragmatic paralysis.

Two infants with progressive spinomuscular atrophy presented with severe diaphragmatic dysfunction, increasing to 9 the number of cases with this clinically distinctive variant of Werdnig-Hoffmann disease. The anterior horn cell lesion was generalized but was exceptionally severe in the cervical spinal cord of our cases. Fiber size disproportion in serial thigh muscle samples indicated that qualitative neuronal dysfunction preceded appearance of typical denervation. Shoulder girdle muscle biopsy may be more appropriate in these infants, whose prognosis appears to be universally poor.