A 69-year-old woman with a 27-year history of rheumatoid arthritis presented to the rheumatology clinic with polyarthralgia of both hands and on her right hand painless subcutaneous nodules that had slowly grown over a year. Physical examination revealed arthritis mutilans with ulnar deviation and yellow masses on the metacarpophalangeal joints of the fingers of the right hand.
The concentrations of C-reactive protein and rheumatoid factor were 1,78 mg/dL (normal range <0,15 mg/dL) and 1096 IU/mL (<15 IU/mL), respectively. Hyperlipidaemia, cryoglobulinemia, hypocomplementemia, and monoclonal paraproteins were not detected.
What is the most likely diagnosis?
