A 31-year-old man presented to the emergency department with a 2-week history of left ear swelling. He had similar episodes over the past 2 years, and a 6-month history of weight loss, fatigue, and generalized aches.
Physical exam revealed a swollen and tender ear, costochondral joints, and left knee. Lab tests showed an elevated erythrocyte sedimentation rate.
What is the likely diagnosis?