P35 | Adverse reaction to rituximab: an unusual case of drug- induced trombocytopenia

R. Capecchi¹, S. Barsotti¹, G. Bini¹, F. Finizola², C. Cois³, E. Citi¹, F. Masi³, G. Linsalata¹, C. Giani¹, J. Rosada¹ | ¹Azienda USL Toscana Nordovest, Pisa, (Livorno), ²Azienda USL Toscana Nordovest, Pisa, (Fivizzano), ³University of Pisa, Italy

Premises: Chemotherapy-induced thrombocytopenia is a common complication. Rituximab, an anti-CD20 monoclonal antibody, induces lysis of B cells only. We describe an acute thrombocytopenia induced by rituximab associated with anaphylaxis and acute kidney failure.
Description of the Case report: A 68-year-old woman affected by splenic marginal lymphoma underwent therapy with rituximab plus standard premedication. During the first infusion, patient showed bilateral low back pain followed by widespread pricking pain, dyspnea and hypotension. She was treated with steroid, O2, ephedrine and sent to the ED. Emergency blood tests revealed severe thrombocytopenia (15,000/mm3), confirmed in citrate, and acute renal failure (creatinine: 1.78 mg/dL). The platelets at baseline were 130,000. Admitted to our department, on therapy with prednisone 50 mg daily a slow recovery of platelet values (25,000->35,000->43,000->60,000/mm3) and a return to basal creatinine were observed. Concomitant infections were excluded. Complement C3 was slightly reduced (85 mg/dL) 3 days after the event, with C4 within limits. The patient was discharged to continue hematological follow-up.
Conclusions: Rituximab-induced thrombocytopenia is a condition of rapid onset with unclear pathogenesis. In this case, the association with an infusion reaction, with a clinical pattern similar to what happens in IV immunoglobulins adverse reaction, suggests immunological mechanisms (complement- or lysis-mediated) responsible for the adverse event.