We report the case of a patient with tardive dystonia and a history of psychiatric illness who showed signs of neuroleptic malignant syndrome (NMS) after chronic treatment with tetrabenazine. The first symptom was a mental status change 'consisting of confusion, disorganized thinking, paranoid delusions, and hallucinations. The patient was initially diagnosed with a psychiatric illness until other clinical features of NMS developed, including low-grade fever, autonomic instability, elevated creatine phosphokinase (CPK) level, and rigidity. After initiating treatment for NMS, motor and autonomic signs resolved, and mental status returned to normal. NMS may appear with initial signs of psychosis; in patients with psychiatric illness this fact may cause a delay in the early recognition of NMS and the initiation of appropriate treatment. In addition, though tetrabenazine is generally considered a safe drug, tetrabenazine-induced NMS may appea after long-term treatment.
Neuroleptic malignant syndrome is a rare, but potentially fatal complication of neuroleptic treatment. It usually occurs within 4 weeks of starting medication, but it can develop at any time during treatment (1). The four major characteristic features of NMS include rigidity, hyperpyrexia, autonomic dysfunction, and mental status changes. Mental status changes, such as mutism or stupor, and psychomotor agitation may be the initial manifestations of this toxic condition (2). Prominent early mental status and behavioral changes in NMS present a diagnostic challenge in patients with chronic psychiatric disorders.
Three previous reports have attributed NMS to tetrabenazine, a catecholamine-depleting agent and dopamine receptor blocker used to treat hyperkinetic movements (3). All three cases have been reported in Huntington's disease patients (4-6). We now report a case of NMS in a patient with tardive dystonia, who showed signs of this disorder after receiving long-term and stable treatment with tetrabenazine. This case illustrates two additional points: insidious mental and behavioral changes may be the first signs of NMS, and during the course of illness, there may be clinical features that resemble those typical of the serotonin syndrome.