Type I fiber atrophy and internal nuclei. A form of centronuclear myopathy?

A 6-year-old boy had a myopathy characterized by central nuclei with type I muscle fiber atrophy and preponderance. Study of the family members demonstrated no abnormalities with the exception of an unusually high incidence of centrally located muclei in the muscle biopsy specimen of the mother. A review of the literature disclosed a limited number of cases with identical morphological abnormalities, suggesting that they constitute a form of centronuclear myopathy with some distinctive clinical features.