Neonatal perifascicular myopathy

Perifascicular atrophy of muscle fibers is generally considered to be a specific feature of autoimmune myopathies, dermatomyositis in particular. We describe a neonate presenting with hypotonia and weakness. A biopsy revealed atrophic and regenerating muscle fibers in a perifascicular distribution, and abnormal alkaline phosphatase activity in neighboring perimysial connective tissue. The weakness was nonprogressive and improved on follow-up even though no long-term treatment was administered. We conclude that the presence of perifascicular myopathic changes and muscle fiber atrophy in infants presenting with hypotonia and weakness is neither diagnostic of progressive dermatomyositis, nor a necessary indication for immunosuppressive therapy.