In contrast to the infantile spinal muscular atrophy type 1 (SMA1; Werdnig-Hoffmann disease) with weakness predominantly of proximal muscles and bell-shaped thorax deformities due to intercostal muscle atrophy, infants with distal spinal muscular atrophy 1 usually present with distal muscle weakness, foot deformities, and sudden respiratory failure due to diaphragmatic paralysis that often requires urgent intubation.
We present the results of clinical and molecular genetic investigations of a family in which the father suffers from distal spinal muscular atrophy and the younger son is affected by infantile autosomal recessive SMA type I.