[Etiopathogenesis of necrotizing arteritis (leukocytoclastic vasculitis)]

The small vessel's necrotizing angiitis (necrotizing microangiitis (NMA), leucocytoclastic angiitis) form a continuous spectrum from the exclusively cutaneous forms of Gougreot, to those which seriously affect the viscera, as the very acute and fatal cases of Zeek, passing through a series of intermediate phases, in which Schönlein-Henoch's purpura is found. In all of these clinical forms, the existence of an allergic mechanism has been suggested from their origin itself and in 1964 Alarcón-Segovia and Brown grouped them under the common denominator of allergic angiitis. Later investigations are far from completely confirming this hypothesis. In isolated cases, the clinical sequence corroborates the hypothesis of a bacterian aetiology (local septic focus), but in the Schónlein-Henoch purpura it has not been proven that there is a greater streptococcus beta-haemolytic frequency is the throat nor a greater number of antibodies in the serum than in normal children or those affected by illnesses not related to rheumatic fever. The aetiologic role of drugs and food is very difficult to prove. The anatomopathologic similarity between the Arthus reaction, the serum sickness and the spontaneous human NMA have led to the hypothesis that the NMA are immunocomplex (IC) diseases. In order to try to prove this, basically three techniques have been used: Direct immunofluorescence to show the IC tissue deposits, and mixed cryoglobulinemia and the serum's anti-complementary activity for the circulating IC. Direct immunofluorescence shows, in approximately 50% of the cases, the presence of IgG and C3 in the damaged vessels (also IgM with frequency). But, are these found combined as complexes? Parish, in some cases of presumably post-bacterial angiitis, has shown the simultaneous presence of the bacterian antigen and the Ig. The direct immunofluorescence negativity can be due to: (1) The IC being rapidly eliminated by the neutrophils; (2) the fact that these are nonimmunologic pathologic cases. On the other hand, the IC deposit could be a passive phenomenon in a previously damaged vessel. With great frequency, mixed cryoglobulinemia is associated with systemic conditions of the auto-immune type (collagenosis, etc) or of the malignant lymphoid haemopathy type, and with NMA. With what frequency is mixed cryoglobulinemia found in the NMA? 33% of the 47 cream's cases. What is the pathogenic relationship between processes? Often the cryoglobulin components are found deposited in angiitis lesions, but its presence and intensity does not guard any relationship with the cryoglobulinemia rate. Besides the 33% of the cases with mixed cryoglobulinemia, 13% serum's anti-complementary activity, and the remaining 54% had no indications of circulating IC with the usual techniques. Of 104 cases of Schónlein-Henoch purpura, 75 of which had nephritis, only 10% had hypocomplementemia. In summary, in about 50% of the patients with NMA, no reasonable indication of IC disease was found...