Large and Medium Vessel Vasculitides

It is noted that vasculitides are infrequent yet clinically challenging diseases because they threaten blood supply to vital organs. Damage to large and medium-sized arteries immediately puts the host at risk for severe clinical consequences, as compensatory mechanisms for losing the function of the aorta and its major branches are very limited. In contrast to non-inflammatory vasculopathies, arteritides are characterized by a combination of ischemic tissue damage and a syndrome of generalized inflammation. Pathogenic mechanisms relevant for these two dimensions of disease may be distinct and respond differentially to therapy. Systemic inflammation is caused by the excessive production of cytokines. In the cases of giant cell arteritis (GCA) and Takayasu's arteritis (TA), induction of an abrupt and massive acute phase response is typical. As part of the acute phase response, patients produce hepatic acute phase proteins that give rise to diagnostically important laboratory abnormalities, such as increases in ESR and C-reactive protein (CRP). Furthermore, the ultimate challenge in understanding GCA and TA remains the identification of the initial triggers of the disease processes.