Rituximab associated late-onset neutropenia-a rheumatology case series and review of the literature.

Recently in the rheumatology literature, Rituximab (RTX) has been associated with late-onset neutropenia (LON), defined as an absolute neutrophil count (ANC) <1.5 × 10(9)/L at least 4 weeks after the last infusion. We determined the incidence of LON in patients with rheumatic disease at a single tertiary medical center, ascertained patient characteristics including results of bone marrow biopsies performed on four neutropenic patients, and performed a literature review. The incidence at our institution was 6.5 %, similar to that reported in the literature. Bone marrow biopsies from four neutropenic patients had the predominant cell line as lymphocytes, comprising an average of 41 % (range 24-50 %) of the cellular aspirate suggesting that there is a selective reduction in granulopoiesis and maturation arrest at the promyelocyte stage. Sixty percent of patients presented without serious infections, and all survived without adverse sequelae. Treatment with granulocyte colony-stimulating factor shortened time to recover of ANC but did not change overall outcomes. Among 25 patients re-challenged with RTX after resolution of LON, only two developed recurrence of LON. Among patients at our institution and identified from a review of the literature, LON is not usually associated with serious infections that lead to significant adverse outcomes, G-CSF therapy does not appear to be necessary as it does not change outcomes, and RTX re-treatment after recovery from LON appears safe.