Rituximab-associated hypogammaglobulinemia: incidence, predictors and outcomes in patients with multi-system autoimmune disease

Rituximab is a B cell depleting monoclonal antibody used to treat lymphoma and autoimmune disease. Hypogammaglobulinemia has occurred after rituximab for lymphoma and rheumatoid arthritis but dataare scarce for other autoimmune indications. This study describes the incidence and severity of hypogammaglobulinemia in patients receiving rituximab for small vessel vasculitis and other multi-system autoimmune diseases. Predictors for and clinical outcomes of hypogammaglobulinemia were explored. We conducted a retrospective study in a tertiary referral specialist clinic. The severity of hypogammaglobulinemia was categorized by the nadir serum IgG concentration measured during clinical care. We identified 288 patients who received rituximab; 243 were eligible for inclusion with median follow up of 42 months. 26% were IgG hypogammaglobulinemic at the time that rituximab was initiated and 56% had IgG hypogammaglobulinemia during follow-up (5-6.9g/L in 30%, 3-4.9g/L in 22% an