Clinical and electron microscopic observation of a case with nemaline myopathy is presented as the report from Japan has been very limited. The patient was a 3 year and 10 m onth old boy who showed marked hypotonia, wryneck and scoliosis since birth. Hematological study and serum chemistry were within. normal limit. E. M. G. demonstrated myopathic pattern. Multiple classical nemali ne bodies (rods) were demonstrated by electron microscopic study of the biopsy of the brachial biceps. Light microscopy of the section stained with Azan and PTAH and thick section of the Epon embeded, toluidine blue stained section also permit identification of the rods in the muscle fibers. Ultrastructural invest igation of the longitudinally sectioned rods revealed sbout 100 Angstrom periodicity parallel to the long axis and occasionally about 150 A striation perpendicular to the long axis. The transverse section of the rods demonstrated regularly arranged cross section of the filaments. The diameter was 55-60Aand the spacing was 90-110A. The filaments of the rods were apparently thinner than the thin filaments of the nearby myofilament and differ from Z band structure.
