MRCP UK EXAMINATIONS

A 43-year-old woman presents to her physician with pain and immobility of the bones in metacarpal phalangeal and feet joints. Similar complains in symmetric pattern were about ulnar and knee joints, though not so severe. Physical examination revealed pastous skin over the joints, a partial ankylosis of metacarpal phalangeal and feet joints, and also ulnar deviation of the hands and flexion-hypertension (’swan neck"or"walrus flipper") deformities of the fingers. In addition, movable firm, rubbery and tender 1cm hypodermic nodules were found in the phalangeal joints area. An aspirate of joint fluid showed increased turbidity and presence of white “grains” ("rice bodies"). Immunofluorescence also revealed the rhematoid factor. What is the most likely diagnosis?