[Microscopic polyarteritis].

Microscopic polyarteritis is an idiopathic necrotising vascularitis of the small vessels. Manifestations include diffuse alveolar haemorrhage, segmentary necrotising glomerulonephritis, and a cutaneous, articular, neurological or digestive vascularitis. The absence of a histological granulomas and medium calibre vessel involvement distinguishes Wegener's syndrome from polyarteritis nodulosa. The diagnosis is facilitated when anti-neutrophil cytoplasm antibodies are found in the serum. These auto-antibodies are suspected to be the cause based on clinical and experimental data, although this aetiology has not been confirmed. Corticosteroids, immunosuppressors and plasmapheresis can improve the prognosis of this severe and evolving affection which may be fatal.