A freeze-fracture study of the plasma membrane of muscle fibres of a patient with chronic creatine kinase elevation suspected for malignant hyperthermia.

The muscle biopsy from a 12-year-old boy with chronic creatine kinase elevation was studied by electron microscopy. At the age of 7 years the patient had a possible abortive attack of malignant hyperthermia. The biopsy specimen contained many fibres with segmental contracture and necrosis; thin sections showed defects of the plasma membrane with loss of glycogen granules into the interstitium. Freeze-fracturing of the plasma membrane showed clustering of intramembranous particles and some membrane areas were devoid of particles and of pinocytotic caveolae. The E-face showed irregular elevations and the P-face corresponding defects. These deviations of the fracture-plane were due to manifest membrane openings, to abnormalities of the structure of the lipid bilayer, to clustering of membrane particles or to the fact that intracellular membranes often were abnormally close to the plasma membrane. The findings suggest that a disintegration of the lipid-protein system of the membrane precedes the formation of manifest defects. The manifest defects resembled those in Duchenne muscular dystrophy. It is unknown whether the changes seen by freeze-fracturing were specific for a myogenic disorder and whether they were due to a basic membrane abnormality or to defects in other systems of the muscle cell.