Abnormal carnitine distribution in the muscles of patients with idiopathic inflammatory myopathy

Abstract

Objective. To analyze the levels of free carnitine and carnitine esters in the muscles of patients with inflammatory myopathies. Methods. Six men and 7 women with inflammatory myopathy and 25 age‐matched healthy controls were studied. Free carnitine and carnitine esters in muscle homogenates were measured by a radiochemical procedure. Muscle histochemical staining and measurement of respiratory chain enzyme activity were also performed. Results. Eleven patients had muscle carnitine insufficiency. Five of them had subsarcolemmal oxidative accumulations, 5 had lipid droplets, and 4 had defects of the respiratory chain enzyme complexes. Conclusion. Abnormal distribution of muscle carnitine is present in patients with inflammatory myopathies and could impair muscle function. Coexistent mitochondrial dysfunction may contribute to carnitine insufficiency.