Tocilizumab preserves renal function in rheumatoid arthritis with AA amyloidosis and end-stage kidney disease: Two case reports

Case 1: A 59-year-old Japanese woman with rheumatoid arthritis (RA) for 36 years was admitted for evaluation of deteriorating renal function. Her serum creatine was 4.2 mg/dL, and proteinuria was 6.5 g daily. Renal and duodenal biopsy revealed AA amyloidosis. After treatment with tocilizumab (a humanized anti-interleukin-6 receptor antibody), proteinuria decreased to 1.1 g daily. The patient’s renal function subsequently remained stable for 8 years. Case 2: A 71-year-old Japanese man with RA for 30 years was admitted due to deterioration of renal function. Serum creatine was 2.9 mg/dL, and urinary protein excretion was 0.06 g daily. Renal and duodenal biopsy identified AA amyloidosis. Tocilizumab was initiated, and his renal function remained stable for 6 years. The 2(nd) duodenal biopsy showed a marked decrease of AA amyloid deposits. Conclusion: These two cases suggest that tocilizumab may preserve renal function in the setting of end-stage kidney disease and shift the point of no return for RA patients with AA amyloidosis and renal dysfunction.