Giant cell arteritis.

In many populations giant cell arteritis (GCA) is the most common form of vasculitis. Genetic markers, ethnic factors, and increasing age over 50 years appear to enhance susceptibility and an infection may trigger its onset. Recent investigations provide evidence that the vasculitic reaction is part of an immune response to an antigen residing in involved artery walls. These studies along with the description of an experimental model of the disease have significantly increased out understanding of GCA.