Slowly progressive generalised muscle weakness and atrophy beginning in childhood; on biopsy of skeletal muscle, the nuclei of most muscle fibres are seen to be located near the centre of a small fibre (the normal position for a 10-week embryo) rather than at the periphery of the fibre; familial incidence. Autosomal dominant recessive and x-linked 310400 forms occur.
Synonym: myotubular myopathy.
distal myopathy, myopathy affecting predominantly the distal portions of the limbs; onset is usually after age 40, with weakness and wasting of small muscles of the hands; The infantile form and the swedish later-onset are autosomal dominant and there is a Japanese late-onset type that is recessive.
Minicore-multicore myopathy, an uncommon nonprogressive myopathy with early onset, proximal weakness, and hypotonia. Muscle fibres show focal defects of oxidative and myofibrillar adenosine triphosphatase enzymes with disorganization of myofibril ultrastructure.
mitochondrial myopathy, weakness and hypotonia of muscles, primarily those of the neck, shoulder, and pelvic girdles, with onset in infancy or chil
dhood; on biopsy, giant, bizarre mitochondria are seen located between muscle fibrils just beneath the sarcolemma. The dominant form is due to deletion of mitochondrial dna and the recessive form is due to a complex deficiency.