Morphologic abnormalities in a case of malignant hyperthermia.

An 8-year-old boy underwent general anesthesia and experienced an episode of malignant hyperthemia, characterized by elevated temperature, cardiac arrhythmias, markedly elevated serum enzymes (SGOT, LDH, and CPK), proteinuria, and hemoglobinuria. Sixty-six days after anesthesia a skeletal muscle biopsy was obtained for examination by electron and light microscopy, which showed skeletal muscle cells with abnormally numerous mitochondria, enlarged, and variable in shape. Some contained abnormal cristae. There were more lysosomes than normal, and lipofuscin was increased in quantity. Myelin-like bodies were also present. Previous reports of muscle abnormalities are reviewed and compared with the data in this case.