Improved outcomes on subcutaneous IgG in patients with humoral immunodeficiency and co-morbid bowel disease.

Immunoglobulin replacement can be life-saving for certain individuals with immunodeficiencies. Subcutaneous IgG (SCIG) is an increasingly used method of replacement over intravenous IgG (IVIG), with potential advantages including fewer systemic side effects, no need for IV access, patient-reported improved quality of life, and decreased cost. However, while patients with certain associated co-morbidities, such as protein-losing enteropathy, may demonstrate more stable IgG levels when on SCIG compared to IVIG, the clinical significance of these experiences is not well described. Using retrospective chart review, we examined three cases in which SCIG and IVIG was administered to patients with either common variable immunodeficiency (CVID) or secondary humoral immunodeficiency and protein-losing gastrointestinal co-morbid disease. Both outpatient and inpatient records were reviewed for data regarding treatment with IVIG versus SCIG, reported frequency and severity of infections, hospitalizations, and IgG levels. All three patients demonstrated improvement in infection rate, stability of IgG levels, and co-morbid disease when on SCIG as compared to IVIG. These findings suggest that the pharmacokinetics of SCIG may translate into more consistent serum IgG levels, contributing to clinical improvement in immunodeficient patients with protein-losing comorbidities when compared to IVIG. Limitations to this study are small patient numbers, retrospective design, and potential therapeutic bias. Further characterization of the effects of co-morbid conditions on immunoglobulin replacement is critical to providing improved and informed patient care.