A case of multiple myeloma misdiagnosed as seronegative rheumatoid arthritis: a rare case report.

Introduction: Multiple myeloma (MM) is a malignant plasma cell proliferation producing large numbers of monoclonal immunoglobulins. Typical MM symptoms include anemia, bone pain, hypercalcemia, and renal failure. Atypical presentations like joint involvement were rarely reported in the literature and may cause significant delays in treatment and adverse outcomes.

Case Presentation: The authors report a case of a 54-year-old female who presented with symmetrical polyarthritis and was misdiagnosed with rheumatoid arthritis. The diagnosis of MM was made after failing many treatments of rheumatoid arthritis and with further laboratory tests and procedures.

Conclusion: This rare manifestation of MM carries a diagnostic challenge and causes a significant delay in treating such patients. Here, the authors report this unusual initial presentation with a review of several cases in the literature describing similar presentations.