Practice question

A 52-year-old woman presents with a 4-month history of pain and swelling affecting the small joints of her hands (MCPs, PIPs) and wrists bilaterally. She experiences significant stiffness in the mornings, lasting for over an hour. She feels generally fatigued. Examination confirms symmetrical synovitis of the affected joints. Blood tests show a raised ESR (55 mm/hr) and CRP (40 mg/L). Rheumatoid Factor (RF) is positive. What is the most likely diagnosis?