Co-occurrence of Systemic ANCA-Associated Vasculitis and Leukocyte Chemotactic Factor-2 Amyloidosis: A Case Report

Le résumé fourni par la source

Leukocyte chemotactic factor-2 amyloidosis is an increasingly recognized cause of renal amyloidosis characterized by extracellular deposition of fibrils derived from the hepatocyte-produced protein leukocyte chemotactic factor-2. Anti-neutrophil cytoplasmic antibody-associated vasculitis is a systemic autoimmune disease characterized by pauci-immune inflammation of small to medium-sized blood vessels that commonly involves the kidneys. To our knowledge, the co-occurrence of systemic anti-neutrophil cytoplasmic antibody-associated vasculitis and leukocyte chemotactic factor-2 amyloidosis has not previously been described. We report a 75-year-old man with anti-proteinase 3 antibody-positive anti-neutrophil cytoplasmic antibody-associated vasculitis manifesting as scleritis without renal involvement, who presented with newly elevated serum creatinine and proteinuria. Laboratory investigations demonstrated elevated inflammatory markers, persistent anti-proteinase 3 antibody positivity, microscopic hematuria without casts, and significant proteinuria. Given concern for rapidly progressive glomerulonephritis, a renal biopsy was performed. Histopathology preliminarily revealed acute tubular injury and nodular glomerulopathy without necrotizing or crescentic glomerulonephritis. Congo red staining demonstrated widespread amyloid deposition involving glomeruli, interstitium, and blood vessels. Amyloid subtyping by mass spectrometry confirmed leukocyte chemotactic factor-2-type amyloid. Kidney function partially improved with supportive management, and treatment to control ongoing systemic inflammation with rituximab was initiated. This case highlights the importance of renal biopsy in patients with anti-neutrophil cytoplasmic antibody positivity and kidney dysfunction, as renal manifestations may not reflect vasculitic involvement. It also describes a previously unreported coexistence of these conditions, which may contribute to future insight into the incompletely understood nature of ALECT2 amyloidosis.

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