Type B3 thymoma associated membranous nephropathy: A rare case and review of the literature

Thymoma can cause several autoimmune conditions in a number of patients. Nephrotic syndrome is considered to be a rare systemic manifestation from thymic lesions. The most common renal pathology associated with thymoma is minimal change disease (MCD). Herein, we reported a case of 58-year-old man with type B3 thymoma, who developed nephrotic syndrome after the tumor recurrence. The renal biopsy showed the morphologic features of membranous nephropathy (MN). Both immunofluorescent study and serum level for phospholipase A2 receptor (PLA2R) antibody were negative, suggesting a secondary type. Literature review suggests that there is a correlation between thymoma subtype and renal pathology, i.e. lymphocyte predominant thymoma (type B1, B2) is associated with MCD, while type B3 thymoma is associated with MN.