[Pubmed] Severe Hypogammaglobulinemia (IgG) During Efgartigimod Therapy in Neurological Practice: A Real-World Case Seri

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Cureus. 2026 Apr 7;18(4):e106599. doi: 10.7759/cureus.106599. eCollection 2026 Apr.

ABSTRACT

Background Efgartigimod is a neonatal Fc receptor (FcRn) antagonist approved for adults with generalized myasthenia gravis (gMG) who are anti-acetylcholine receptor antibody-positive, and for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). By blocking FcRn-mediated IgG recycling, efgartigimod lowers circulating IgG and reduces pathogenic autoantibodies. Clinical trials have demonstrated efficacy and an overall acceptable safety profile, but patients with low baseline IgG were generally not well represented. Objective The main objective of this study is to describe severe reductions in serum IgG observed in routine neurologic practice during efgartigimod therapy, and to explore their potential clinical implications, including infection risk and management considerations. Methods We performed a retrospective case series of 10 patients treated with efgartigimod in our practice between 2025 and 2026 for CIDP and MG. Available clinical data were reviewed, including diagnosis, prior immunotherapy exposure, baseline IgG (when available), serial IgG measurements, nadir IgG, and any documented infectious complications. Results Several patients developed marked hypogammaglobulinemia during treatment, including profound reductions to levels below 100 mg/dL in selected cases. Several patients reached IgG levels within ranges associated with increased susceptibility to infection (

Source: https://pubmed.ncbi.nlm.nih.gov/4211010 ... 0&v=2.20.0