Management of leukocytoclastic vasculitis.

Leukocytoclastic vasculitis (LcV) is the most common form of vasculitis of the skin and usually results from deposition of immune complexes at the vessel wall. It presents in different forms and in association with different diseases. When IgA is the dominant immunoglobulin in immune complexes, systemic involvement is likely in both children and adults (Henoch-Schönlein purpura--HSP). LcV due to IgG- or IgM-containing immune complexes has less systemic involvement and a better prognosis than HSP. Other forms of LcV include cryoglobulinaemic, urticarial and ANCA-associated LcV as well as LcV associated with vasculopathy and coagulopathy in SCLE/SLE or in bacteraemia/sepsis. The aim of diagnostic guidelines is to determine the specific type and systemic involvement of LcV and to identify an underlying cause. Basic work-up should encompass history of drug intake and of preceding infections, biopsy with immunofluorescence, differential blood count, urine analysis and throat swabs. Therapy of immune complex LcV often does not require aggressive therapy due to a usually favourable course. It includes avoidance or treatment of eliciting agents and use of compression stockings to reduce purpura. There are no large prospective randomized controlled studies. Corticosteroids are indicated when there are signs of incipient skin necrosis. In chronic or relapsing LcV we suggest colchicine as a first-line and dapsone as a second-line therapy. Corticosteroids may reduce the incidence of severe renal insufficiency in children according to some studies, but there is no study showing such an effect in adults. Severe systemic vasculitis requires immunosuppressive strategies.

NADPH oxidase is required for neutrophil-dependent autoantibody-induced tissue damage.

The contribution of phagocyte-derived reactive oxygen species to tissue injury in autoimmune inflammatory diseases is unclear. Here we report that granulocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase crucially contributes to tissue injury in experimental models of the antibody-mediated autoimmune disease epidermolysis bullosa acquisita. Neutrophil cytosolic factor 1-deficient mice lacking functional NADPH oxidase were resistant to skin blistering by the passive transfer of antibodies against type VII collagen. Pharmacological inhibition or deficiency of human NADPH oxidase abolished dermal-epidermal separation caused by autoantibodies and granulocytes ex vivo. In addition, recruitment of granulocytes into the skin was required for tissue injury, as demonstrated by the resistance to experimental blistering of wild-type mice depleted of neutrophils and of CD18-deficient mice. Transfer of neutrophil cytosolic factor 1-sufficient granulocytes into neutrophil cytosolic factor 1-deficient mice demonstrated that granulocytes provide the NADPH oxidase required for tissue damage. Our findings identify granulocyte-derived NADPH oxidase as a key molecular effector engaged by pathogenic autoantibodies and provide relevant targets for prevention of tissue damage in granulocyte-mediated autoimmune diseases.