MSFinals-2735

A 26-year-old man visits his GP with complaints of joint stiffness that has been bothering him for the past month. The stiffness is at its worst in the early morning and improves with use. He has no medical history, but his family has a history of psoriasis and vitiligo. The patient smokes about ten cigarettes per day and recently recovered from a viral throat infection two days ago.

During the examination, the doctor notices swelling in the patient’s left knee and 1st and 2nd metatarsophalangeal joints of his right foot. The swelling is accompanied by tenderness and reduced range of active and passive movement. What is the most probable diagnosis?