Development of serum sickness-like symptoms after rituximab infusion in two patients with severe hypergammaglobulinemia.

Rituximab is a monoclonal antibody that depletes B cells and is commonly used for the treatment of autoimmune diseases. In this report, we describe 2 patients with autoimmune diseases and marked hypergammaglobulinemia attending at a tertiary care hospital, who, following treatment with rituximab, developed a severe serum-sickness-like reactions. Both patients were treated with intravenous corticosteroids, recovered well, and on follow-up, were negative for the development of human antichimeric antibodies. Based on these and other similar cases in the literature, we propose that severe hypergammaglobulinemia due to autoimmune conditions may be a predisposing factor for the development of a serum sickness-like reaction after treatment with Rituximab, which can sometimes occur without prior exposure to this antibody. Rheumatologists should be aware of this possible association when prescribing this medication.