Risperidone-induced marked elevation of serum creatine kinase in adolescence. A case report.

We report on a 17-year-old boy who developed a marked increase in serum creatine kinase (CK) (9743 U/l) during treatment with risperidone for catatonic psychosis. Known causes of elevated CK such as delirium, malignant neuroleptic syndrome, infection, cocaine overdose, trauma, and intramuscular injections were ruled out. Vital signs remained always within the normal range. On discontinuation of risperidone, serum CK concentrations returned to 105 U/l within 1 week and remained within normal limits. While a transient moderate increase in CK activity at admission may be related to acute psychosis, risperidone seems to be the causative agent for the later marked elevation. To our knowledge, this is the first reported case of risperidone-associated elevation of serum CK in an adolescent. While discontinuation of risperidone does not seem necessary in patients with a moderate increase of serum CK, withdrawal of neuroleptics is warranted in more severe cases.