Large-vessel GCA or a late presentation of Takayasu's arteritis?

Giant cell arteritis (GCA) is a vasculitis that involves medium- and large-sized vessels. Typically presenting with localised headache, temporal artery tenderness, jaw claudication and ophthalmological complications, it can also affect large vessels, leading to limb claudication. We describe a patient presenting with acute coronary syndrome but who was also noted to have absent upper limb pulses, leading to a speculative diagnosis of GCA. According to the American College of Rheumatology, the patient met the criteria for both giant cell arteritis and Takayasu's arteritis. The gold standard investigation for diagnosing GCA is the temporal artery biopsy. Although contemplated, it was argued by the reviewing rheumatologist that this would not alter her management. She was thus commenced on prednisolone 60 mg daily, which led within 2 days to a rapid fall in erythrocyte sedimentation rate to 66 mm/h, and by day 11 this had dropped further to 4 mm/h.