Abstract
We estimated serum levels of cardiac muscle myosin light chain I(MLC-I) in 109 patients with neuromuscular diseases including progressive muscular dystrophy. The localization of cardiac type MLC-I is not only in the cardiac muscle but also in the red fiber of the skeletal muscle. Most patients with Duchenne dystrophy showed an elevated serum MLC-I level, which had significantly negative correlation with age in a mode of an exponential formula. And, in some cases in the advanced stage, we could not detect significant elevation. Becker dystrophy also revealed an increased serum level. In these patients with X-linked muscular dystrophy, serum MLC-I level demonstrated a significant positive correlation with serum CK level. Elevated serum MLC-I level was also observed in several cases of limb-girdle dystrophy, myotonic dystrophy and neurogenic amyotrophy. These findings suggested leakage of the fragment of muscle structural protein into the circulation. Further studies are needed for the establishment of clinical usefulness such as assessment of muscle breakdown in the neuromuscular diseases.
