[Significance of serum myosin light chain-1 level in neuroleptic malignant syndrome].

In Parkinson disease, the interruption of medication often results in neuroleptic malignant syndrome, which is caused by acute inhibition of the dopaminergic system. It is a serious question in the management of Parkinson disease, whether episode of pyrexia is derived from neuroleptic malignant syndrome or other origins. In this syndrome, muscle damage enhances serum titers of myogenic enzymes and proteins. Myosin light chain-1 (MLC-1), which is a small fragment of myosin, has been reported to show long lasting elevation compared with CK in neuromuscular diseases and cardiac infarction. Then, we evaluated the clinical significance of serum MLC-1 in six patients with neuroleptic malignant syndrome, i.e., four cases of Parkinson disease, one multiple system atrophy and one schizophrenia with acute administration of haloperidol. Muscle breakdown was observed by the elevation of serum MLC-1 titer, which sustained several days after normalization of serum CK titer. In two cases of Parkinson disease, high level of serum MLC-1 was observed in spite of normal body temperature, which suggested pre-clinical stage of neuroleptic malignant syndrome. Thus, we concluded that the estimation of serum MLC-1 is useful in those patients with high risk of neuroleptic malignant syndrome.