Rituximab Induced Late Onset Neutropenia

Rituximab is a monoclonal antibody against CD20 a leucocyte cell marker expressed on normal and neoplastic B lymphocytes .Although first used for treatment of CD20 positive non-hodgkin’s lymphoma it’s use has expanded to include a varied spectrum of diseases mostly autoimmune disorders. Thus it is used in the treatment of autoimmune haemolytic anaemia, immune thrombocytopenia, rheumatoid arthritis, pemphigus vulgaris, vasculitis and many more autoimmune conditions.

Rituximab is generally a well tolerated drug although many acute and delayed adverse effects are noted. Rituximab induced late onset neutropenia [LON] is a rare and life threatening adverse effect which needs to be suspected in patients presenting with neutropenia after four weeks of completing Rituximab therapy.

We report a case of a 73year old man who presented with severe grade 4 neutropenia of 0.04x109/L and life threatening sepsis 19 weeks after treatment of autoimmune haemolytic anaemia with four doses of Rituximab. He recovered with prompt initiation of G-CSF and made a complete recovery.

LON is a delayed drug-induced reaction, which appears several months (usually 1 to 5 months) after cessation of rituximab treatment. With widespread use of Rituximab for autoimmune diseases in different medical disciplines it is important that these physicians are aware of and monitor patient’s post-Rituximab therapy for this delayed reaction.