Clozapine is an atypical antipsychotic approved by the Food and Drug Administration for treatment-resistant schizophrenia and also indicated for the reduction in risk of recurrent suicidal behavior in patients with schizophrenia or schizoaffective disorder. The most serious side effect of clozapine treatment is agranulocytosis, which is defined as an absolute neutrophil count (ANC) < 0.50 × 109 per L. Benign ethnic neutropenia (BEN) is a condition found in members of African or Middle Eastern descent that is characterized by ANC < 1.50 × 109 per L in the absence of other causes. Filgrastim is a granulocyte colony-stimulating factor (G-CSF) that has shown efficacy in reducing the duration of agranulocytosis in some patients who develop clozapine-induced agranulocytosis. It is currently unknown whether filgrastim is beneficial in the treatment of neutropenia due to BEN. We here, for first the time report a case of a patient with BEN who developed agranulocytosis both during the first clozapine trial for schizophrenia and during the rechallenge, despite early stabilization with filgrastim treatment, which highlights the failure of filgrastim in treating BEN.

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