The pathophysiology of this condition is based on immunopathological processes that are classified into 3 types: glomerulonephritis mediated by antibodies against the glomerular basement membrane (Goodpasture disease); glomerulonephritis mediated by immunocomplexes (systemic lupus erythematosus, post-streptococcal, Henoch-Schonlein purpura) and Pauci-immune glomerulonephritis (ANCA-positive vasculitis with specificity for proteinase 3 - PR3 or myeloperoxidase - MPO). The gene discussed is MPO; the disease is Henoch-Schoenlein purpura.