Case Report: Elderly anti-GBM antibody disease with diffuse non-hereditary glomerular basement membrane thinning of uncertain etiology.

Anti-glomerular basement membrane (GBM) antibody disease is an autoimmune-mediated rapidly progressive renal injury. The coexistence of diffuse non-hereditary glomerular basement membrane thinning of uncertain etiology in elderly patients is clinically rare and poses substantial challenges in differential diagnosis and clinical management. We herein report a 70-year-old female patient admitted for elevated serum creatinine for more than 20 days. After a prodromal infection, she rapidly progressed to anuria and acute kidney injury (AKI), with markedly elevated serum anti-GBM antibody levels. Renal biopsy revealed crescentic glomerulonephritis, and electron microscopy demonstrated diffuse thinning of the glomerular basement membrane; genetic testing excluded hereditary thin basement membrane nephropathy. The patient received methylprednisolone pulse therapy, cyclophosphamide immunosuppression, plasma exchange, and maintenance hemodialysis. Long-term dynamic monitoring of antibody levels and imaging indicators was performed after discharge. During hospitalization and follow-up, anti-GBM antibody levels declined continuously, subsequent infection was gradually controlled by antimicrobial therapy, and the patient remained hemodialysis-dependent with stable overall condition. Renal biopsy combined with genetic testing is the core method to distinguish lesions of diffuse non-hereditary glomerular basement membrane thinning of uncertain etiology, from hereditary basement membrane lesions. This case represents an elderly patient with oligoimmune atypical anti-GBM antibody disease and diffuse non-hereditary glomerular basement membrane thinning of uncertain etiology, and this long-term follow-up record provides valuable clinicopathological reference for individualized treatment and prognostic evaluation of similar rare cases.