[Hypersensitivity angiitis or microscopic polyarteritis nodosa. Recent findings. II. Clinical aspects].

Hypersensitivity angiitis is one of the commonest necrotising vasculitides. Given the ubiquitous distribution of the small blood vessels almost any part of the body may be affected. However benign forms predominantly involving the skin are the most common. Forms predominantly involving the viscera and that may prove fatal are rare. Among the polymorphous skin lesions encountered "palpable purpura" is the most common and its palpability is a vital element in differential diagnosis. Among non-cutaneous sites the kidneys are the most frequent and glomerular involvement is the commonest cause of death. Though laboratory tests provide no specific data they may indicate the severity of visceral involvement.