Successful treatment with humanized anti-interleukin-6 receptor antibody (tocilizumab) in a case of AA amyloidosis complicated by familial Mediterranean fever

Familial Mediterranean fever (FMF) is a well-known cause of secondary AA amyloidosis. Colchicine is generally considered to be the most effective treatment for FMF and FMF-associated amyloidosis, but the management of patients who are refractory to colchicine remains controversial. We encountered a 51-year-old Japanese man with suspected FMF, who had periodic fever with abdominal pain, polyarthritis, and nephropathy (serum creatinine of 1.9 mg/dL and 24-h protein excretion of 3.8 g). FMF was diagnosed by mutation analysis of the Mediterranean fever (MEFV) gene, which revealed that the patient was compound heterozygous for the marenostrin/pyrin variant E148Q/M694I. AA amyloidosis was diagnosed by renal and gastric biopsy. Colchicine was administered, but his arthritis persisted, and serum creatinine increased to 2.4 mg/dL. Therefore, a humanized anti-interleukin-6 receptor antibody (tocilizumab) was administered at a dose of 8 mg/kg on a monthly basis. Both arthritis and abdominal pain subsided rapidly, and C-reactive protein (CRP) decreased from 2.5 to 0.0 mg/dL. After 2 years, his serum creatinine was decreased to 1.5 mg/dL and proteinuria was improved to 0.3 g daily. In addition, repeat gastric biopsy showed a marked decrease of AA amyloidosis. This case suggests that tocilizumab could be a new therapeutic option for patients with FMF-associated AA amyloidosis if colchicine is not effective.