Severe T- and B-cell immune deficiency associated with malignant thymoma

Immunodeficiency with thymoma syndrome is a rare disorder that generally occurs after the fourth decade of life. Typically, thymic tumors are benign, and gradually developing immunodeficiency consists of hypogammaglobulinemia with low B-cell counts and an inverted CD4+/CD8+ T-cell ratio due to excessive CD8+ T cells.

To report the case of a 32-year-old, white man with an invasive malignant thymoma and profound combined T- and B-cell immunodeficiency associated with a normal CD4+/CD8+ T-cell ratio, absence of circulating B cells, and infection with an unusual organism.

The patient presented with a superior vena cava syndrome caused by a malignant thymoma. During chemotherapy and radiotherapy, he experienced recurrent episodes of pulmonary infections due to Haemophilus influenza and Serratia marcescens and persistent oral thrush. He was diagnosed as having thymoma and underwent immunological evaluation.

Sixteen months after the diagnosis of thymoma, the immunological evaluation revealed profound lymphopenia, eosinopenia, very low counts of both CD4+ T cells and CD8+ T cells, and a normal CD4+/CD8+ ratio with negative delayed-type hypersensitivity skin test results. Hypogammaglobulinemia and absent specific antibody responses were associated with a lack of peripheral blood CD19+ B cells. Despite treatment with intravenous immunoglobulin, the patient died of respiratory insufficiency and sepsis secondary to a chronic pulmonary infection.

Malignant thymoma may be associated with severe combined immunodeficiency. A normal CD4+/CD8+ ratio and the absence of peripheral B cells suggest a bone marrow defect that affects both T and B cells in the pathogenesis of this syndrome. Comprehensive immunological evaluation should be performed when thymoma is diagnosed to initiate an early and effective treatment to prevent life-threatening complications.