Immuno-deficient features of thymoma-associated myasthenia gravis patients with hypogammaglobulinemia: A condition comparable to Good's syndrome.

Good's syndrome (GS) is a rare immunodeficiency disorder associated with thymoma, characterized by hypogammaglobulinemia and recurrent infections; however, its clinical significance in thymoma-associated myasthenia gravis (TAMG) remains unclear. We retrospectively reviewed 30 patients with TAMG admitted to our center between January 2010 and March 2022. We defined GS-like immunodeficiency as serum IgG below the institutional cutoff of 861 mg/dL and a history of two or more infections requiring antimicrobial treatment; 11 patients (36.7%) met this definition. Compared with the remaining patients, the GS-like group had higher incidences of malignancy (45.5% vs. 5.3%, p = 0.016) and autoimmune diseases other than MG (36.4% vs. 5.3%, p = 0.047), lower peripheral lymphocyte counts (median 1100/μL vs. 2200/μL, p = 0.0051), and more frequent airflow obstruction defined by one second to forced vital capacity ratio of less than 70% (60.0% vs. 5.3%, p = 0.0026). Five deaths occurred in the GS-like group, and none in the other; median survival from the first antimicrobial-treated infection was 5.0 years. These findings imply that TAMG patients with GS-like immunodeficiency have a worse prognosis, underscoring the need for close monitoring and timely adjustments of MG management. (189 words).