Clinical case: idelalisib-induced immunoglobulin flare.

IgM flare is a transient, treatment-induced, increase of monoclonal IgM levels in lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) patients. Until recently this phenomenon was observed in patients treated with Cladribine and Rituximab. Here we report a case of a heavily pretreated chronic lymphocytic leukemia patient with an atypically high immunoglobulin production who developed clinically significant immunoglobulin flare following Idelalisib treatment.