Neuroleptic malignant syndrome with slight elevation of creatine kinase in serum: a brief review.

Neuroleptic malignant syndrome (NMS) is the most severe adverse effect that can be caused by antipsychotics. It is an acute potentially fetal and idiosyncratic reaction that may be produced with any medication affecting the central dopaminergic system with an estimated frequency of 0.51% of the neuroleptic-treated patients.1 Its four main clinical manifestations are hyperthermia, severe muscle rigidity, autonomic nervous system dysfunction and altered level of consciousness.2 Laboratory findings consist in elevation of the creatine kinase (CK) plasma levels and leukocytosis. Specifically, elevation of CK in plasma has been described in more than 90% of the cases.3,4 NMS more frequently occurs with first generation neuroleptics. However, it is believed that it can be caused by any antipsychotic drug.5 The physiopathological mechanism causing it is still unknown. It has been suggested that a marked reduction in central dopamine activity resulting from D2 receptor blockage in the nigrostriatal pathway, in hypothalamus, in the mesolimbic and mesocortical pathway can explain some of the symptoms (as the rigidity, hyperthermia and mental status dysfunction).6,7 The diagnosis is clinical, and when a patient under treatment with antipsychotics has fever and muscle rigidity, CK plasma levels should be determined since they are a useful marker for the early detection of NMS.8 The cases that do not occur with elevation of CK in plasma are rare, and as far as we know, only three cases have been reported in which this elevation has not occurred.9-11