Takayasu arteritis and giant cell arteritis: are they a spectrum of the same disease?

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are forms of large-vessel vasculitides that affect the aorta and its branches. There is ongoing debate about whether they are within a spectrum of the same disease or different diseases. Shared commonalities include clinical features, evidence of systemic inflammation, granulomatous inflammation on biopsy, role of T-helper (Th)-1 and Th17 in the pathogenesis, and, abnormalities of the aorta and its branches on imaging. However, there are also several differences in the geographic distribution, genetics, inflammatory cells and responses to treatment. This review highlights the similarities and differences in the epidemiology, pathogenesis, clinical manifestations, imaging findings and treatment responses in these conditions. Current data supports that they are two distinct conditions despite the numerous similarities.