Continuation with clozapine after eosinophilia: a case report.

Background: Clozapine-induced eosinophilia had been reported in several studies about blood dyscrasias in clozapine-treated patient. The largest study with 2404 patients in Italy found the incidence of 2.2% by criteria of more than 0.4 × 109 /l. Associated cases of pancreatitis, hepatitis, colitis, nephritis, and myocarditis were reported. Interestingly, incidence of myocarditis is high in Australia, but low in the rest of the world. In the following, we will present a case of clozapine-induced eosinophilia which spontaneous resolution was noted under continuation of clozapine.

Case presentation: "Mr. L" was a 54-year-old single, jobless man. He had treatment-resistant chronic schizophrenia with onset at age 28. He had received electroconvulsive therapy twice prior to this admission. After admission, a trial of clozapine was started with an initial dose of 100 mg/day, and gradually titrated to 200 mg/day. He experienced notable improvement after 2 weeks with decreased auditory hallucinations and no more self-harm behaviors, but he also developed eosinophilia. A medical workup was performed and showed no signs of end-organ inflammation. We continued clozapine use and closely monitored complete blood count with a differential test to track his eosinophil count by the recommendation of the hematology service. His eosinophil count decreased then and remained within normal limits 3 weeks later. The dosage of clozapine was gradually raised as high as 400 mg/day. His psychotic symptoms got partial remission and continued to show no signs of end-organ inflammation at the time of discharge.

Conclusions: The pathophysiology of clozapine-induced eosinophilia is still unknown, but resolution of eosinophilia despite ongoing clozapine treatment suggests the possibility of an acute allergic reaction. Signs or symptoms of organ inflammation are important for management of eosinophilia. In this case report, we demonstrated that if eosinophilia occurred without signs or symptoms of organ inflammation, it may be justified to continue clozapine use under careful monitoring.