Subcutaneous Immunoglobulin for Antibody Deficiency in Antineutrophil Cytoplasmic Antibody (ANCA)-associated Vasculitis

Objectives Intravenous immunoglobulin G (IVIG) is used to treat antineutrophil cytoplasmic antibody (ANCA) patients with recurrent infections as a result of hypogammaglobulinemia (HG) induced by treatment regimens. We sought to characterize clinical features, treatment, and outcomes for patients treated with the novel subcutaneous IgG (SCIG) for the aforementioned purpose.  Methods We conducted a retrospective study of 136 patients in our ANCA database to identify patients with recurrent infections and HG subsequently treated with SCIG. Patient demographics, serologies, treatment, and immunological parameters were assessed.  Results Of 136 patients, four were treated with SCIG. All were Caucasian, proteinase-3 (PR3)-positive, and the majority (n = 3) were females. All patients had pulmonary involvement, and regimens of cyclophosphamide (CYC) and/or rituximab (RTX) were employed for induction and remission. Three patients each experienced recurrent bouts of respiratory tract infections and shingles. Ig levels (G, M, and A) were reduced in all patients, except for one patient who had normal IgA levels. CD19/20 cells were depleted and CD3/4/8/NK cells were preserved in all patients. Three patients had no discernible antibody response to the pneumococcal vaccine (specific pneumococcal serotypes measured pre- and post-vaccine). The mean duration elapsed between the first rituximab administration and commencement of SCIG was 7.2 years. The IgG level normalized and none of the patients had a recurrence of infection since the initiation of SCIG.  Conclusion This data, albeit preliminary, is the first series that demonstrates SCIG can be a reliable alternative to IVIG in ANCA patients with recurrent infections secondary to HG. Early identification of this subset of patients is likely to mitigate infectious risks, associated morbidity, and hospitalization.