Olanzapine-induced neutropenia in a patient with systemiclupus erythematosus: a role of FcγRIIIb polymorphism?

In this study, we report the case of a Chinese patient with systemic lupus erythematosus (SLE) who developed neutropenia after treatment by olanzapine for the SLE-related psychiatric symptoms. The relationship between agranulocytosis, SLE and olanzapine is still unknown. Fcγ receptor IIIb (FcγRIIIb) is a low-affinity receptor, constitutively expressed only by neutrophils; NA1 and NA2 have been identified as representing polymorphisms of FcγRIIIb. NA1 is associated with the incidence of autoimmune neutropenia and is particularly frequent in Asiatic ethnic groups. The Chinese patient resulted to be homozygous for NA1. We suggest that the presence of NA1 allele may be a predisposing factor to olanzapine-induced agranulocytosis in patients with SLE. Hence, the analysis of FcγRIIIb polymorphism should be investigated in other cases of antipsychotic-induced agranulocytosis.