Summary

Characterised by the association of a thymoma, hypogammaglobulinaemia, and B-cell and T-cell dysfunction, Good's syndrome (GS) is a rare cause of adult immunodeficiency leading to recurrent infections, and autoimmune manifestations related to the thymoma. We describe a 70-year-old woman in whom the diagnosis of GS was made after 7 years follow-up of a monoclonal gammopathy of undetermined significance (MGUS). After thymectomy, she received monthly intravenous immunoglobulin perfusions in order to maintain a normal plasmatic IgG level. To our knowledge, this is the fifth described case of GS associated with an MGUS. This rare condition should not be misdiagnosed, as the prognosis is determined by infectious and autoimmune complications, which could be prevented.