Mean serum creatine kinase activity in patients with functional psychoses.

Increased serum creatine kinase (CPK) activity has been reported to be present during acute exacerbations of psychosis in the majority of patients with the major "functional" psychoses. It has also been demonstrated that mean serum CPK activity, ie, average daily serum CPK activity, is under genetic control. In this report, we present evidence for an association between the presence of a transient elevation of serum CPK activity beyond the upper limit of normal during psychotic episodes and relatively high mean serum CPK levels during the rest of hospitalization. The magnitude of the transient serum CPK elevation was correlated with mean serum CPK activity in psychotic patients. The mean serum CPK level was also correlated with the terminal innervation ratio, an indication of alpha motor neuron dysfunction. The incidence of serum CPK elevations in first-degree relatives of psychotic patients was significantly greater in patients with high mean serum CPK activity than in those with low mean serum CPK activity. High mean serum CPK activity may be an indication of an increase in permeability of the muscle cell membrane, which in turn may be due to some defect in the neurotrophic regulation of muscle physiology or an independent expression of muscle abnormalities.