The Set up and the Triggers: An Update on the Risk Factors for Giant Cell Arteritis.

PURPOSE OF REVIEW: To describe recent research relevant to factors which predispose to giant cell arteritis (GCA) and those which trigger its manifestation, with particular emphasis on the more recent and controversial associations (COVID-19, vaccination, novel medications) which have changed the medical landscape and perhaps GCA prevalence.

RECENT FINDINGS: GCA remains more prevalent in Caucasians but nevertheless affects other racial groups. Certain HLA haplotypes (i.e. DRB1*04) incurs risk of GCA. Polymyalgia rheumatica remains a strong association, and recent evidence also associates GCA with hematologic malignancy. COVID-19 infection may trigger GCA, in addition to vaccination (particularly the COVID-19 vaccine) and reactivated VZV infection, though the latter may be related to a common trigger. PD1-inhibitors may be associated with GCA. Previously establish patterns in geography and latitude are supported. A seasonal pattern of GCA in the summer/spring months is suggested but not proven. Controversy regarding GCA risk factors exists, as well as to whether the overall prevalence of GCA is rising. Given the growing aging population, the total number of cases of GCA will certainly increase, a challenge to which that our healthcare system must continue to rise to meet.