[Angiitis caused by hypersensitivity or microscopic polyarteritis nodosa. Recent findings. I. Nosographic aspects].

Hypersensitivity angiitis or microscopic polyarteritis nodosa is one of the necrotising angiitis and was not distinguished from classic polyarteritis nodosa until the Fifties. The present study examines the nosographic aspects of necrotising angiitides with reference to the anatomohistological, aetiopathogenic and clinical criteria proposed by various Authors for their identification and with emphasis on the fact that all these factors must be borne in mind for the purpose of diagnosis. The factors that make it possible to distinguish hypersensitivity angiitis from other necrotising angiitides are, at clinical level, the presence of skin lesions, and in anatomohistological terms the involvement of the small blood vessels and leucocytoclasia.