Giant Cell Arteritis

Giant cell arteritis (GCA), a primary angiitis of large and medium-sized arteries, occurs almost exclusively during the sixth to eighth decades of life. Pathogenic events are initiated by organ-specific dendritic cells (DC) close to the vasa vasorum network of three-layered arteries. Such DC participate in immunosurveillance and recognize pathogen-associated and danger-associated molecular patterns. Early inflammation is mediated by Th17 cells; chronic vasculitis relies on IFN-γ-producing Th1 cells suggesting two separable pathogenic pathways. Temporal artery biopsy remains the diagnostic approach of choice. Imaging of the vascular lumen and vessel wall by magnetic resonance imaging or computed tomography are instrumental to capture large vessel involvement. GCA is treated with corticosteroids; convincing data that other immunosuppressants have significant steroid-sparing action or can treat steroid-resistant disease is currently lacking. Whether GCA enters remission is unknown and whether continuous immunosuppression prevents sequel of smoldering vasculitis is not established. Avoiding corticosteroid overuse is critical in patient care. Skillful management requires accurate distinction between aggressive inflammation (high dose therapy necessary), stable disease (watchful monitoring) and progressive vascular damage (low dose, long-term treatment may be warranted).