29th January 2024

Background

Epidemiology 

Giant cell arteritis (GCA) or temporal arteritis is the most common form of vasculitis in adults. Almost all patients with GCA are over the age of 50, with a peak incidence of 70-90 years of age. There is a female predominance. Although it can occur in all racial groups, it is most common in people of Scandinavian descent. Around 22 people per 100,000 aged over the age of 50 will develop GCA.

Aetiology

The exact cause of the condition is unknown. Possible contributing factors include genetic predisposition (e.g. human leukocyte antigen HLA-DR4) and viral infections (e.g. parvovirus B19). Up to 50% of patients with giant cell arteritis also have polymyalgia rheumatica (PMR).

Pathophysiology

The activation of dendritic cells in the blood vessel walls leads to the recruitment of lymphocytes and monocytes. The differentiation of monocytes into macrophages and giant cells augments the inflammatory process by producing cytokines. This process leads to the destruction of vessel wall structures and concentric intimal hyperplasia. There is resultant reduction in blood flow and ischaemia. GCA commonly involves external carotid artery branches (especially temporal artery), as well as the aorta and vertebral arteries.