TY - JOUR T1 - Lumpers and Splitters: Ongoing Issues in the Classification of Large Vessel Vasculitis JF - The Journal of Rheumatology JO - J Rheumatol SP - 149 LP - 151 DO - 10.3899/jrheum.141376 VL - 42 IS - 2 AU - PETER C. GRAYSON Y1 - 2015/02/01 UR - http://www.jrheum.org/content/42/2/149.abstract N2 - Large vessel vasculitis (LVV) is defined as inflammation that affects the aorta and its major branches. Takayasu arteritis (TAK) and giant cell arteritis (GCA) are the 2 main forms of LVV1. Historically, GCA is considered a disease of the elderly that targets the extracranial arteries (e.g., carotid and temporal arteries). In contrast, TAK typically affects younger patients and targets the aorta and its primary branches (e.g., subclavian and renal arteries). However, increasing evidence, primarily based on radiographic studies, demonstrates that vasculitic involvement of the aorta and primary branches can occur in GCA in addition to the more widely recognized cranial features of the disease2. Current estimates about the prevalence of involvement of the aorta and primary branches in GCA vary widely across different cohorts, but large vessel pathology is apparent by angiography in about 20%–30% of patients with GCA3,4. There are no existing guidelines regarding screening for large artery involvement in GCA, so the incidence of large vessel disease in GCA may be underestimated. An older necropsy study of 4 patients with GCA and known temporal arteritis, in which there was no clinical suspicion for vasculitis in the aorta and branch vessels, demonstrated widespread vasculitic lesions throughout the large arteries in every patient5. Cumulative incidence rates of large vessel involvement in GCA have increased dramatically over the last 2 decades in parallel with increased awareness about this feature of GCA6.Recognition of involvement of vessels beyond the extracranial arteries as a feature of GCA has created new challenges in the disease classification of LVV. The 1990 American College of Rheumatology (ACR) Classification Criteria for GCA were developed in a time when involvement of the aorta and primary branches was not a well-recognized feature of GCA and are focused … Address correspondence to Dr. P.C. Grayson, National Institutes of Health, 10 Center Drive, Building 10, 6N Rm 216G, Bethesda, Maryland 20892, USA. E-mail: peter.grayson{at}nih.gov ER -