Pathophysiology
Th17/Th1 driven granulomatous inflammation with multinucleated giant cells in the media of large arteries. Overlaps with polymyalgia rheumatica (~50%). Peak age 70-80 y; strong female predominance.
Sources: ACR/VF 2021 GCA Guideline (Arthritis Rheumatol 2021;73:1349); EULAR 2018 LVV Recommendations (Ann Rheum Dis 2020;79:19); NEJM Tocilizumab GiACTA (2017;377:317)
Clinical presentation
New unilateral temporal headache, jaw claudication, scalp tenderness, visual loss (amaurosis fugax or sudden painless loss), constitutional symptoms, and PMR (shoulder/hip stiffness). Aortic involvement: aneurysm, dissection.
Diagnosis
ESR typically >50 mm/h and CRP elevated. Confirm with temporal artery biopsy (1.5-2 cm segment, look for granulomatous inflammation) or high-resolution vascular ultrasound (halo sign) - do not delay steroids for biopsy.
Management
Start high-dose glucocorticoids immediately on clinical suspicion: prednisone 40-60 mg/day (or IV methylprednisolone 500-1000 mg/day for 3 days if visual symptoms). Add tocilizumab (weekly SC) as steroid-sparing per GiACTA. Low-dose aspirin considered for ischaemic complications. Taper steroids over 12-24 months monitoring for relapse.
Complications & follow-up
Permanent vision loss (~15%), aortic aneurysm/dissection (screen with imaging), steroid-induced diabetes/osteoporosis (calcium/vitamin D + bisphosphonate).
