A systemic disease mimicking a rheumatoid arthritis

Introduction. - Rare systemic diseases such as amyloidosis can mimic inflammatory rheumatic diseases. Because of their poor prognosis, physicians should rule them out at the onset of inflammatory rheumatism. We report a case of AL amyloidosis misdiagnosed as rheumatoid arthritis. Case report. - A 71-year-old woman was referred for seronegative rheumatoid arthritis, resistant to three biologic therapies. She had an IgA - lambda monoclonal gammopathy of undetermined significance (MGUS). The patient subsequently developed glomerular proteinuria. Abdominal fat and accessory salivary glands biopsies revealed amyloid light-chain (AL) amyloidosis. Treatment with bortezomib-cyclophosphamide-dexamethasone, led to complete hematologic, renal and rheumatologic remission. Ten months after treatment interruption, the patient had an articular and hematologic relapse. Conclusion. - Amyloid light-chain amyloidosis arthropathy is probably underdiagnosed. A review of amyloid arthropathy associated with multiple myeloma found that 33% of patients had been misdiagnosed with rheumatoid arthritis. (C) 2019 Societe Nationale Francaise de Medecine Interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.