Increased serum myosin light chain 3 level in neuromuscular diseases

Abstract
A radioimmunoassay for human skeletal muscle myosin light chain 3 (MLC‐3) was developed. The serum level of MLC‐3 was evaluated in 143 patients suffering from neuromuscular diseases. Increased MLC‐3 level was observed in muscular dystrophies. There were significant positive correlations between serum levels of MLC‐3 and creatin kinase (CK) in Duchenne and limb‐girdle type muscular dystrophy, but the regression lines were different. Patients with neurogenic amyotrophy, especially amyotrophic lateral sclerosis, also showed elevated MLC‐3 levels with or without high CK, and the frequency of increase in MLC‐3 was greater than that of CK. The results of the present study suggest that circulating MLC might be a useful marker for muscle breakdown not merely in myopathies but in neurogenic disorders.