Olanzapine-induced leukopenia with human leukocyte antigen profiling

Olanzapine is an atypical antipsychotic medication frequently used in the m anagement of psychotic states. While it has proved to be safe compared to c lozapine with regard to haematotoxicity, because it has only been available for a few years, full documentation of its haematological side-effects rem ains incomplete. We report a case of olanzapine-induced leukopenia with ass ociated neutropenia. Since clozapine-induced haematotoxicity has been assoc iated with characteristic human leukocyte antigen (HLA) groups, HLA typing was determined in this patient. Following failure with typical antipsychoti c medication, the patient received 10 mg/day of olanzapine. Three weeks lat er, he developed fever and a significant decrease in leukocyte count. Olanz apine was immediately discontinued. HLA typing was determined. The white ce ll count returned to normal and the fever, most probably secondary to the l ow white cell count, subsided with antibiotic treatment. HLA typing results were: A1 24, B7, B35, DRB1*15, DRB1*11, DRB3*01-03, DRB5*01-02. Olanzapine may induce serious leukopenia and neutropenia. HLA typing in this single p atient demonstrated a distinct haplotype compared to that previously observ ed in clozapine-induced haematoxicity. Int. clin. Psychopharmacol 16:55-57 (C) 2001 Lippincott Williams & Wilkins.