Clozapine and Thrombocytopenia: Case Report & Literature Review

BACKGROUND: Clozapine, an atypical antipsychotic has the strongest evidence for efficacy in treating refractory schizophrenia. Total and differential leukocyte counts are monitored in clinical practice to prevent agranulocytosis. Thrombocytopenia is less common with incidence of 3-8% over one year of initiation but at times prove fatal. CASE REPORT: A 35-year-old married lady, with family history of mental illness in first degree relatives presented with 10 years history of psychotic illness. She was a known case of bronchial asthma and dyslipidaemia. She had failed adequate trials of multiple antipsychotics medication including monotherapies of risperidone, olanzapine, quetiapine, haloperidol and aripiprazole in the past. Clozapine was started and titrated to dose of 400 mg over few weeks considering diagnosis of Treatment Refractory Schizophrenia. Leukocyte counts - TC and DC were monitored regularly. She responded to Clozapine therapy however when complete blood counts were checked after 9 weeks of initiation of Clozapine due to an exacerbation of asthma, significant thrombocytopenia (26000/mcl) was found. Clozapine was abruptly stopped. Platelet count increased to baseline levels after 2 weeks. By then psychotic symptoms had re-emerged. Clozapine was restarted and counts were monitored. There were no haematological problems in follow up. DISCUSSION: Clozapine-induced thrombocytopenia is a less well-known, but potentially serious adverse effect. The case highlights the fact that besides monitoring the leucocyte count, platelet count could also be monitored for patients on Clozapine, especially in those with comorbidities. It also shows that one can try to rechallenge Clozapine with close monitoring despite an episode of thrombocytopenia.