You are answering a USMLE-style medical question. Question: A 72-year-old woman comes to the physician because of a 1-month history of frequent headaches, double vision, fatigue, and myalgias. Physical examination shows pallor, tenderness to palpation over the temples, and inward deviation of the left eye. Laboratory studies show an erythrocyte sedimentation rate of 65 mm/h. Temporal artery biopsy shows transmural granulomatous inflammation and fragmentation of the internal elastic lamina. Treatment with high-dose intravenous corticosteroids is begun. The patient's condition puts her at greatest risk of developing which of the following complications? Options: A) Pulmonary hypertension B) Lower extremity gangrene C) Palpable purpura D) Thoracic aortic aneurysm Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.