[Clinico-pathological significance of the immunostaining of myosin heavy chain isoforms in pathological human skeletal muscle].

Expression of the four myosin heavy chain isoforms (fast-twitch, slow-twitch, neonatal and embryonal isoforms) was immunohistochemically observed in 500 biopsied limb muscles of neuromuscular disorders. Fast-twitch isoform was expressed in type 2A, 2B and pathologic 2C fibers. Slow-twitch isoform was expressed in type 1 and 2C fibers. Embryonic isoform was expressed in regenerating type 2C fibers of active myopathies such as Duchenne dystrophy and polymyositis. Expression of neonatal isoform, which was longer positive than that of embryonic isoform, was noted in regenerating fibers, denervated fibers and highly atrophic fibers in chronic myopathies of limb-girdle dystrophy and myotonic dystrophy. In conclusion, the immunostaining of MHC isoforms are useful to make a clinico-pathological diagnosis to determine the stages in evolution of regeneration or degeneration of pathologic muscle fiber per se.