Unexpected fibrous mediastinitis in a patient with myasthenia gravis - a case report

BACKGROUND: Fibrous mediastinitis (FM) is a rare mediastinal lesion characterized by proliferation of fibrous tissue within the mediastinum. Previous reports have shown that this lesion can be caused by histoplasmosis and tuberculosis. In extremely rare cases, FM can also be caused by autoimmune diseases such as antineutrophil cytoplasmic antibody-associated vasculitis and large-vessel arteritis. CASE PRESENTATION: In our case, we report unexpected fibrous mediastinitis found after robotic thymectomy in a patient with myasthenia gravis (MG). The preoperative imaging indicated no obvious lesion in the mediastinum and the patient denied histories of both histoplasmosis and tuberculosis. After the operation, both proliferation of fibrous tissue and ectopic germinal centres (GCs) could be found in the thymus. CONCLUSION: This rare case might enrich our knowledge of the relationship between FM and autoimmune diseases.