Congenital myopathy with ringlike distribution of myonuclei and mitochondria and accumulation of nemaline rods. A variant of centronuclear myopathy?

Histopathologic and ultrastructural findings in a muscle biopsy performed on an 11-year old boy with congenital hypotonia, weakness, respiratory insufficiency requiring chronic ventilatory support, and a probable X-linked inheritance are presented. The muscle biopsy disclosed a peculiar, ringlike arrangement of mitochondria and myonuclei in most muscle fibers. Accumulations of nemaline rods were present in approximately 10-15% of fibers. We believe that our patient represents a variant of myotubular/centronuclear myopathy. The histochemical findings suggest disturbance in developmental migration of nuclei and mitochondria probably due to impaired function of the cytoskeleton.