A 35-year-old woman presents with a 2-week history of tender nodules on her lower legs, fatigue, and low-grade fever. She has no recent infections or medication changes but reports chronic cough and shortness of breath for the past month. Examination reveals tender erythematous nodules on the anterior shins. A chest X-ray shows bilateral hilar lymphadenopathy. What is the most likely underlying cause of this patient’s condition?
