Clozapine-induced agranulocytosis in a native American: HLA typing and further support for an immune-mediated mechanism

Background: Approximately 30% of schizophrenic patients defined as treatment refractory significantly improve with clozapine. However, clozapine produces agranulocytosis in approximately 1% to 2% of patients in the United States. The mechanism of clozapine-induced agranulocytosis has not been established, but evidence suggests an immune-mediated mechanism. Method: Human leukocyte antigen (HLA) typing was performed in a native American with clozapine-induced agranulocytosis. Results: Our findings support previous observations of a role of the HLA-B16, DR4, DQw3 haplotype in predicting susceptibility to agranulocytosis in clozapine-treated patients. Conclusion: We suggest that HLA typing of clozapine candidates may be useful for predicting the risk for clozapine-induced agranulocytosis.