Risk of Infection Following Clearance of Immunoglobulin G by Plasma Exchange in Myasthenia Gravis

Management of myasthenia gravis (MG) includes reduction of pathogenic IgG autoantibodies by intravenous immunoglobulin (IVIg), B-cell depletion, therapeutic plasma exchange (TPE), and neonatal Fc receptor (FcRn) blockers. Concerns exist that chronic IgG reduction could lead to more frequent infections. We assessed the frequency and severity of infection with associated serum IgG levels during infections in MG patients treated with chronic TPE in both inpatient and outpatient settings.

MG patients treated with chronic TPE at a single center from April 2014 through December 2022 were included. All serum IgG levels from this cohort were recorded. Reported infections were limited to those who had clinically reported symptoms, supportive laboratory findings, necessitated inpatient admission for infection, or were treated with antibiotics/antivirals.

Twenty-three patients were included. Ninety-seven infections were identified, with the majority of these being respiratory (36%) or urinary (22%). There were no differences in median serum IgG levels found during active infection versus periods of non-infection (657.3 [IQR: 459.5-823.1] and 518 [IQR: 472.9-672.5] mg/dL, respectively, Wilcoxon's p = 0.47). Infections necessitating inpatient admission did not have reduced median serum IgG compared with less severe infections or periods of non-infection (515.75 [IQR: 457.0-799.1], 660.5 [IQR: 472.9-808.4], and 518 [IQR: 467.8-672.5] mg/dL, respectively, pairwise Wilcoxon's p = 0.84). No correlation was identified between the number of reported infections per patient and their median serum IgG levels throughout the study period (Spearman's p = 0.26, p = 0.23).

In this small retrospective study, there was no association between IgG levels and infections in patients with MG treated with chronic TPE.