gms | German Medical Science

Introduction: Immunosuppressive treatment may lead to the development of secondary hypogammaglobulinemia, which may facilitate the occurrence of recurrent and potentially severe infections. Secondary hypogammaglobulinemia is especially common with B-cell-targeted therapy [1], but which other factors may increase the risk for hypogammaglobulinemia remains uncertain. Development of secondary hypogammaglobulinemia over time so far has not been studied in detail.

Methods: Retrospective monocentric cohort study of 939 patients with ANCA-associated vasculitis (AAV), giant cell arteritis (GCA) or spondyloarthritis (SpA) recruited from a rheumatology outpatient clinic of a German university hospital.

Results: A cohort of 939 patients with AAV, GCA or SpA was screened. Of these, initial immunoglobulin values were available from 681 patients (189 GCA, 212 AAV, 280 SpA). Mean baseline IgG levels were 11.3 g/l for AAV patients, 9.52 g/l in GCA patients, respectively 11.7 g/l for SpA patients (normal range 7–16 g/l). After 1 year of treatment, IgG levels of AAV patients had decreased on average by 2.56 g/l (SD 3.85, p<0.0001), GCA by 1.58 g/l (SD 5.18, p=0.0005) compared to 0.68 g/l in SpA patients (SD 1.97, p<0.0001). 54.7% of GCA patients had developed at least mild hypogammaglobulinemia (IgG<7 g/l) after 1 year of treatment, compared to 27.8% of AAV patients and 2.9% of SpA patients.

At 2–3 years after initial diagnosis, immunoglobulin levels in GCA patients had increased again by on average 0.75 g/l (p=0.0006), whereas IgG levels in AAV patients had slightly further decreased by on average 0.37 g/l (SD), though not statistically significant. In SpA patients IgG levels had remained stable (-0.08 g/l, p=0.5586). At >5 years after diagnosis IgG levels remained largely stable.

In a logistic regression model, diagnosis of GCA (OR 13.22, p<0.001) and AAV (OR 10.22, p<0.001), initial IgG level (OR 0.78, p<0.001) and age (OR 1.04, p<0.001) significantly predicted hypogammaglobulinemia at 1 year of treatment.

Conclusion: Secondary hypogammaglobulinemia is common especially in patients with vasculitides, but may be transient. A significant decrease of immunoglobulin levels is observed particularly within the first year after treatment initiation. Immunoglobulins should be monitored on a regular basis and patients should be assessed for occurrence of infections, which should trigger further work-up.

Disclosures: No conflicts of interest.

Table 1 [Tab. 1]