Mr. B is а 50-yeаr-оld mаn presenting with a 6-mоnth histоry of progressively worsening joint pain, stiffness, and swelling. He reports morning stiffness lasting more than an hour, affecting both hands, wrists, and knees. He also complains of fatigue and low-grade fevers occasionally. There is no significant family history of autoimmune diseases. Mr. B works as a computer programmer and has noticed difficulty with typing due to joint pain in his fingers. Clinical Examination: On examination, Mr. B appears fatigued but is alert and oriented. There is bilateral tenderness, warmth, and swelling of the proximal interphalangeal joints, metacarpophalangeal joints, and wrists. He has limited range of motion in these joints due to pain. Cardiovascular and respiratory examinations are unremarkable. Laboratory Findings: Complete blood count: Normal. Erythrocyte sedimentation rate (ESR): Elevated. C-reactive protein (CRP): Elevated. Rheumatoid factor (RF): Positive. Anti-cyclic citrullinated peptide (anti-CCP) antibodies: Positive. Joint aspiration: Synovial fluid analysis shows inflammatory changes. What is the most likely diagnosis based on Mr. B's clinical presentation and laboratory findings?