Case Report: Renal amyloid A amyloidosis with crescent formation and elevated serum anti-glomerular basement membrane antibody titers in a patient with chronic systemic inflammation

We report a case of a 65-year-old Chinese man with chronic systemic inflammation, who presented with nephrotic syndrome and renal insufficiency, along with elevated serum anti-glomerular basement membrane (GBM) antibody titers, yet lacked the typical clinical features of rapidly progressive glomerulonephritis (GN). Renal biopsy demonstrated AA amyloid deposition in the glomerular mesangium, crescent formation in 33% of glomeruli, and patchy immunoglobulin G (IgG) staining. Persistent inflammation, mediated by pathways involving interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), is considered to be associated with the expression of serum amyloid A (SAA) and subsequent AA amyloidogenesis. Furthermore, we hypothesize that persistent inflammatory activity may be a contributory factor in the exposure of cryptic GBM antigens, thereby triggering the production of anti-GBM antibodies. In summary, we report a rare case of renal AA amyloidosis with crescent formation and elevated serum anti-GBM antibody titers in a patient with chronic systemic inflammation. However, the pathogenesis of crescent formation in this patient remains unclear and requires further investigation.