Two inflammatory vascular diseases often show multinucleated macrophages: Takayasu's disease and Horton's disease. Takayasu's disease is a segmentary panarteritis most prominent in the adventitia. Lesions show an inflammatory infiltrate close to the external elastic lamina. Progressive stenosis of the artery, sometimes complicated by calcifying atheroma is the typical course. Horton's disease or temporal arteritis is another segmentary arteritis. Lesions show a mixed inflammatory infiltrate partly localized in the adventitia where there are T CD4+ lymphocytes secreting II-2 and IFN-gamma and also macrophages expressing TGF beta 1, IL-6 and IL-1 beta, and partly situated in the interior part of the wall, around the internal elastic lamina, and mostly made of macrophages and giant cells which produce TNF, collagenase and nitric oxide that are responsible for destruction of the wall. The variety and subtleness of some lesions do not always make a precise diagnosis possible. But any inflammatory vascular lesion, even slight, can reveal a systemic vasculitis.