Multicentric Castleman disease (MCD) is a rare systemic lymphoproliferative disorder and is infrequently associated with renal complications that include amyloid A (AA) amyloidosis. Although it has been reported that patients with MCD and amyloidosis usually have a poor prognosis, recently, tocilizumab, a humanized anti-interleukin-6 receptor antibody, has emerged as an effective and specific treatment for AA amyloidosis secondary to chronic inflammatory disorders. Here we report a case of an MCD patient with secondary AA renal amyloidosis who was successfully treated with tocilizumab. The patient was initially referred to nephrology specialists because of a decline in renal function and proteinuria. Percutaneous renal biopsy revealed the presence of Congo red-positive amorphous depositions and AA protein-positive areas in glomeruli, vessel walls, and interstitium, confirming a diagnosis of renal AA amyloidosis secondary to MCD. At 1 year after starting tocilizumab treatment, a second renal biopsy showed the clearance of amyloid deposits in the interstitium. These observations suggest that tocilizumab may be an effective therapy for AA amyloidosis secondary to MCD.
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