Navigating coexisting autoimmunity and immunodeficiency in thymoma: a case report of TAMA, Good's syndrome, and myasthenic crisis.

The coexistence of thymoma-associated multiorgan autoimmunity (TAMA) and Good's syndrome creates a challenging clinical scenario in which autoimmunity and profound immunodeficiency occur simultaneously. Here, we report a 37-year-old female with invasive WHO Type B3 thymoma and myasthenia gravis (MG) who developed progressive erythroderma-like skin lesions with graft-versus-host disease-like interface dermatitis. Immunological evaluation revealed marked hypogammaglobulinemia, absent circulating B cells, reduced CD4+ T cells, and an inverted CD4+/CD8+ ratio. During a subsequent myasthenic crisis, severe immune dysfunction and active pulmonary infection were already present. Because conventional rapid immunomodulatory options were limited, efgartigimod and eculizumab were administered sequentially. The pulmonary infection continued to progress, and the patient ultimately died. This case highlights the importance of immune and infection risk assessment before potent immunomodulatory therapy.