[Epidemiology and natural history of giant cell arteritis]

Knowledge of the natural history and epidemiology of giant cell arteritis (GCA) is growing. With the recent conceptual change, GCA is no longer considered a disease with mandatory cranial symptoms but, rather, a larger disease spectrum also including idiopathic aortitis in people older than 50 and polymyalgia rheumatica with large-vessel involvement. The incidence peak between age 70 and 80 years, greater frequency in females and greater occurrence in Nordic countries are well-established epidemiological characteristics. Conversely, the notion that the incidence of GCA is increasing is challenged by several recent population-based studies suggesting a trend reversal for about 15 to 20 years. The known link with the allele HLA-DRB1*04 was confirmed by a genome-wide association study that also found associations with two other genetic polymorphisms. Recent studies indicating a link with varicella zoster virus infection have invigorated the hypothesis of an infectious cause for GCA. Smoking is the most solidly recognized environmental risk factor, but other traditional cardiovascular risk factors do not seem to predispose to GCA. Evidence is mounting that overall mortality in GCA patients is at best slightly higher than expected in relation to general population mortality data, but GCA is associated with an increase in morbidity and mortality specifically related to aortic aneurysm or other cardiovascular causes. Further studies are needed to integrate the current knowledge into a single etiological model.