[Sporadic Z disk myopathy with accumulation of rods and cytoplasmic bodies].

An unusual myopathy with extensive myofibrillar degeneration related to the Z disk is reported. Focal Z disk disappearance, accumulation of numerous rods and cytoplasmic bodies and some rimmed vacuoles represented the major pathologic features of this sporadic muscular disorder, sharing common clinical and electrophysiological features with inclusion body myositis. This diagnosis was excluded because all nuclei appeared normal and 15-18 nm filaments were not observed in cytoplasm or in the vicinity of membranous whorls. Intramuscular innervation was studied by vital staining with methylene blue: the terminal innervation ratio was normal, indicating a myopathic disorder. The relationship between the present disorder and cytoplasmic bodies and nemaline myopathies is discussed.