Neuroleptic Malignant Syndrome Induced by Olanzapine in a Patient with Huntington's Disease.

Olanzapine is an atypical antipsychotic that binds to a large number of neurotransmitter receptors, including the dopamine D1, D2, and D4, serotonin and histamine receptors. Its antipsychotic effects are likely the result of potent antagonism at dopamine and serotonin receptors [1]. It is frequently used in Huntington’s disease (HD) since it reduces chorea, is a mood stabilizer, augments antidepressants and also encourages weight gain [2]. Olanzapine has probably a better evidence base than the other atypical antipsychotic drugs [3] (with the exception of clozapine) including beneficial effects on the gait disorder and the psychiatric disturbance of HD. Its side effects should always be balanced before starting treatment and include excessive sedation, parkinsonism, tardive dyskinesia and negative metabolic side effects. Neuroleptic malignant syndrome (NMS) has been reported with the use of dopamine depleting agents and other dopamine blockers in HD [4] but to our knowledge, it has never been reported with olanzapine use in patients with HD.