Antineutrophil cytoplasmic antibody-positive giant cell arteritis: Small-vessel vasculitis mimicking large-vessel vasculitis.

Giant cell arteritis is the most common vasculitis in those over 50 years old with a peak incidence between 70 and 80. Symptoms include a new-onset headache, scalp tenderness, jaw/tongue claudication, and visual symptoms, which can be sight-threatening. We report a case of an 82-year-old lady who presented with typical symptoms of giant cell arteritis and bilateral halo sign on an ultrasound scan. Despite initial steroid treatment she deteriorated and developed neurological symptoms including mononeuritis multiplex. Following further investigations, it was found that she was suffering from granulomatosis with polyangiitis and treatment was adjusted accordingly with additional immunomodulating treatment preventing further progression of symptoms. This case highlights how granulomatosis with polyangiitis can mimic giant cell arteritis and should be considered in refractory cases.