D1.348 - Retrospective Evaluation of Laboratory and Clinical Characteristics of Pediatric Patients Diagnosed with IgG Subclass Deficiency and Receiving Intravenous Immunoglobulin Replacement Therapy

Immunoglobulin G subclass deficiency (IgGSD) is a heterogeneous antibody deficiency characterized by recurrent infections despite normal total IgG levels. In selected pediatric patients with significant infection burden and inadequate vaccine responses, intravenous immunoglobulin replacement therapy (IGRT) may be required. However, data regarding the clinical, immunological, and genetic characteristics of these patients remain limited. Retrospectively evaluate the clinical features, immunological phenotypes, allergic comorbidities, and molecular genetic findings in pediatric patients diagnosed with IGSD who received IGRT.

A total of 113 pediatric patients (aged 2–18 years) diagnosed with IgGSD and treated with intravenous immunoglobulin (IVIG) between January 2021 and August 2025 were included. Demographic data, infection patterns, IgG subclass profiles, lymphocyte subsets, atopic status, vaccine responses, and next-generation sequencing (NGS) results were retrospectively analyzed.

The most common immunological phenotype was isolated IgG3 deficiency (23.9%), followed by IgG3 deficiency accompanied by IgA deficiency (22.1%). Recurrent upper respiratory tract infections were the leading indication for IGRT (44.2%). Atopy was detected in 21.2% of patients, most frequently associated with house dust mite sensitization. Flow cytometric analysis revealed decreased NK cell levels in 15.8% of evaluated patients. NGS analysis identified primary immunodeficiency–associated variants in 46.3% of tested patients, with NFKB1 and TNFRSF13B being the most frequently affected genes.

Pediatric patients with IGSD requiring IGRT exhibit a broad clinical and immunological spectrum, frequently accompanied by cellular immune abnormalities and monogenic primary immunodeficiency–associated variants. These findings highlight the importance of comprehensive immunological evaluation and early genetic screening to optimize diagnosis, prognosis, and long-term management.