Parvovirus B19 reactivation presenting as neutropenia after rituximab treatment.

A patient with primary biliary cirrhosis and associated refractory immune thrombocytopenic purpura was treated with 4 weekly courses of rituximab, a monoclonal antibody targeting B-cell surface antigen CD20. Her thrombocyte count and even cholestatic liver function tests improved. However, 17 weeks after rituximab treatment, she developed severe neutropenia (absolute neutrophil count 0.23x10(3)/mul) and recurrent thrombocytopenia with abnormal bone marrow of all three lineages. Although delayed-onset neutropenia has been reported after rituximab, reactivated viral infections have also been encountered. Parvovirus B19 was suspected and confirmed as the cause of neutropenia in our patient. The patient was supported by GCSF treatment and recovered uneventfully after several weeks. Neutropenia after rituximab can also be the predominant manifestation of reactivated parvovirus B19 infection and have a favorable prognosis.