Giant cell arteritis versus Takayasu's Arteritis: Two sides of the same coin?

There are multiple vasculitides which are distinguished based on multiple criteria, including size of affected vessels, distribution of vessels affected, histopathologic differences, genetic factors, and age at presentation. Takayasu's arteritis (TkA) and giant cell arteritis (GCA) are the two main medium to large vessel vasculitides. These vasculitides are associated with different racial predilections, vascular distributions, age groups, diagnostic criteria, and treatments. Nevertheless, the many shared histopathologic features, genetic factors, and overlap in presentation of these two diseases suggest that they may actually be variable presentations of the same disease process, i.e., large vessel vasculitis. This article will review the genetics, histopathology, disease mechanisms, and diagnostic criteria for both TkA and GCA. Overall, despite major advances our understanding of these two diseases, it is still debated whether these two large vessel vasculitides represent two distinct diseases processes or simply variations of the same disease.