[Intractable vasculitis: general consideration-concept and classification: pathological aspects].

Vasculitis may be defined as an inflammatory process, primarily affecting the vascular wall which possesses an architecture, such as organ or tissue, and accordingly may not include the capillary. Since the walls are destroyed, secondary circulatory disturbances may be associated and produce vasculitic symptoms, which are nonspecific in most instances. Although the pathogenesis of most vasculitides is well understood, the lack of knowledge of the etiology makes it difficult to establish a satisfactory classification of vasculitis. The inflammatory lesions tend to be distributed along the course of the vessels throughout the body in most systemic vasculitic syndromes but long segments are frequently affected in the arteritides of large arteries. In recent years, a classification, useful for understanding the clinical manifestations of these vasculitic disorders, is based on the predominant size of the involved vessels, which may be categorized into large arteries (aorta and its primary branches), medium-sized to small muscular arteries and small vessels (arterioles and venules). Certain vasculitides may occur as a primary disease process, whereas others may be associated with other primary disorders. In general, idiopathic primary vasculitides have an extremely poor prognosis and are intractable. However, recent advances of drug therapies in the early stage of the systemic necrotizing vasculitides, such as Wegener's granulomatosis, has bettered prognosis. In the patients with Takayasu's arteritis, life has been prolonged over more than ten years. As a result, additional problems, such as luminal stenosis or dilatation of the involved vessels, have occurred.