Giant cell arteritis and Takayasu aortitis: morphologic, pathogenetic and etiologic factors.

Overlapping features among aortitides are relatively common although the underlining etiologies may differ. Thus, the clinical classification of aortitides is rather difficult and often misleading. Furthermore, morphologic characterizations of these vascular disorders are frequently overlapping and therefore additional clinical and radiologic information is usually required. The greater challenge is aortitides is whether the initiation is due to an exogenous stimulus or due to an autoantigen.