BACKGROUND: Acquired thymic disease (malignant thymoma or thymic hyperplasia) is associated with various autoimmune diseases, such as myasthenia gravis (MG), pure red-cell aplasia (PRCA), pemphigus vulgaris or systemic lupus erythematosus (SLE). Renal disease has rarely been observed in association with thymoma. METHODS: This retrospective, multicentric study collected data on patients with thymic disease and biopsy-proven renal involvement. RESULTS: Twenty-one patients were studied (age: 49+/-14 years; male/female ratio: 8/13). Thymic pathology revealed mostly high-grade malignant thymoma (B2 and AB type); two cases were associated with non-malignant thymic hyperplasia. MG was found in nine out of 21 cases, SLE in three, PRCA in three and pemphigus in two. In 47% of these cases, nephropathy occurred after curative treatment of thymoma (108+/-83 months; range: 8-180 months), mainly based on surgical thymectomy associated with radiotherapy. Clinical and laboratory findings included nephrotic syndrome (75%), renal failure (50%), frequent presence of antinuclear antibodies and hypogammaglobulinaemia. Renal pathology showed minimal change disease in 14 patients and focal segmental glomerulosclerosis (FSGS) in one. Membranous nephropathy was observed in four cases, ANCA-associated glomerulonephritis in two and thrombotic microangiopathy in one. Most patients with minimal change disease or FSGS (11/13) were steroid-sensitive. Despite good response to steroids, 38% of patients died from thymoma and 17% developed end-stage renal failure. CONCLUSIONS: Glomerulopathy can be associated with thymoma or thymic hyperplasia. The present series shows that minimal change disease is the most frequent thymoma-associated glomerular lesion and that it may occur several years after thymectomy.