Response to: ' Biases in Large Vessel Vasculitis ' by Mukhtyar

We thank Mukhtyar for his interest in our report showing the differences of giant cell arteritis (GCA) based on the presence of large vessel involvement (LVI) [1] and for providing some meaningful comments to deepen the discussion [2]. First, Mukhtyar wonders the accuracy of the term of large vessel GCA (LV-GCA). Certainly, it is anatomically correct to use the term ‘cranial or extracranial GCA’ because the Chapel Hill Consensus defines the arteries outside an organ as large vessels, including the superficial temporal artery and the ophthalmic artery distributed in the cranial region [3]. However, ‘LV-GCA’ is also a commonly used term to refer to GCA involving the aorta and/or its branches [4, 5]. Currently, it is still chaotic about the terminology, and the unification is awaited. Second, distinction between GCA and Takayasu arteritis (TAK) is an important and challenging problem. In our cohort, we don’t have any patients that meet the 1990 American College of Rheumatology (ACR) classification for TAK [6], nor the 2022 ACR/EULAR classification criteria for TAK [7]. However, the differentiation of GCA and TAK can be problematic, especially in patients around the age threshold with stenoses of the aortic branches. The 2022 ACR/EULAR classification for TAK and GCA [7, 8] focused on clinical information such as the distribution of affected arteries, and this will help us differentiate GCA and TAK. Also, some recent studies focus on GCA or TAK using genetic or molecular approaches [9]. That kind of research from the perspective of basic medicine can contribute to distinguishing GCA and TAK, and further research is anticipated.