Autoimmune Paraneoplastic Diseases Associated With Thymoma and Thymic Carcinomas

Autoimmune paraneoplastic diseases are associated with thymoma but rarely with thymic carcinomas.[6-9]

The occurrence of autoimmune paraneoplastic diseases in patients with thymoma is related to defective negative selection of autoreactive T cells. Decreased expression of AIRE, the autoimmune regulator gene, contributes to this process.[10] Thymoma-associated autoimmune paraneoplastic disease also involves an alteration in circulating T-cell subsets.[11,12] The primary T-cell abnormality may be related to the acquisition of the CD45RA+ phenotype on naive CD4+ T cells during terminal intratumorous thymopoiesis, followed by the export of these activated CD4+ T cells into the circulation.[13]

In addition to T-cell defects, B-cell lymphopenia and the presence of anticytokine antibodies have been observed in patients with thymoma-related immunodeficiency, resulting in an increased risk of developing opportunistic infection.[6,14,15]

The most common autoimmune paraneoplastic diseases associated with thymoma are myasthenia gravis, hypogammaglobulinemia, and autoimmune pure red cell aplasia.

A variety of other autoimmune paraneoplastic diseases can be associated with TETs and include virtually any organ system.[7,9]

Thymoma patients with myasthenia gravis or other autoimmune paraneoplastic diseases are typically diagnosed with early-stage disease and are more likely to undergo complete surgical resection than those who do not have autoimmune paraneoplastic diseases.[9,20] Thymectomy may not significantly improve the course of thymoma-associated autoimmune paraneoplastic disease in all cases.[21,22] The presence of autoimmune paraneoplastic disease also does not appear to be an independent prognostic factor in patients with TETs.[9]