Abstract: FR-PO0685
A Case Report of NELL-1-Positive Membranous Nephropathy Associated with Thymoma
Session Information
- Glomerular Diseases: Membranous Nephropathy, FSGS, and Podocytopathies
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics
Authors
- Suzuki, Haruka, Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Sugioka, Sayaka, Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Yamamoto, Shinya, Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Yanagita, Motoko, Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan
Introduction
It is widely recognized that malignant neoplasms can induce paraneoplastic glomerulonephritis, including membranous nephropathy (MN). While thymoma-associated nephopathy is relatively uncommon, type B1 and B2 thymomas are mainly linked with minimal change nephrotic syndrome, whereas type B3 thymoma is associated with MN. New antigens associated with MN such as neural epidermal growth factor-like 1 (NELL-1) have been discovered in the past few years. However, the relationship between NELL-1 and thymoma-associated MN has not been reported. Here, we present the first report of NELL-1 positive MN associated with thymoma.
Case Description
A 73-year-old male was noted to have proteinuria during a routine health examination, but received no treatment. Five months later, CT scan revealed a thymoma, and thymectomy was performed. Pathological diagnosis demonstrated type B2 thymoma with a component of type B3 thymoma. Three months post-surgery, pleural effusion persisted, alongside the development of severe proteinuria (10.0 g/gCr) and hypoalbuminemia (1.5 g/dL). The kidney biopsy indicated thickening and duplication of the glomerular basement membrane (GBM). Immunofluorescence staining revealed a granular staining in the capillary walls for IgG (predominant deposition of IgG1 and IgG2), C3, κ and λ. In electron microscopy, widespread subepithelial electron-dense deposits was observed. Staining for PLA2R and THSD7A was negative, whereas NELL1 staining exhibited segmental positivity along GBM. These findings led to a diagnosis of thymoma-associated membranous nephropathy. Consequently, prednisolone treatment was initiated 3 months after thymectomy. His proteinuria improved to 0.3 g/gCr within six months following the treatment.
Discussion
In this case, nephrotic syndrome preceded thymoma by several months and persisted for 3 months after thymectomy, but responded to prednisolone. The pathogenesis of thymoma-associated MN remains unclear; however, the type B3 component may have contributed. Failure of thymectomy alone to induce remission may reflect ongoing autoantibody production. Review of 9 reported thymoma-associated MN cases showed heterogeneous clinical courses and treatment responses, highlighting the need for further case accumulation to clarify pathogenesis.