We report four heterozygous dynamin 2 (DNM2) mutations in five centronuclear myopathy patients aged 1 to 15 years. They all presented with neonatal hypotonia with weak suckling. Thereafter, their phenotype progressively improved. All patients demonstrated muscle weakness prominent in the lower limbs, and most of them also presented with facial weakness, open mouth, arched palate, ptosis, and ophthalmoparesis. Electrophysiology showed only myopathic changes, and muscle biopsies showed central nuclei and type 1 fiber hypotrophy and predominance. Our results expand the phenotypic spectrum of dynamin 2–related centronuclear myopathy from the classic mild form to the more severe neonatal phenotype. Ann Neurol 2007