Rapidly progressive glomerulonephritis (RPGN): is there still an "idiopathic" subgroup?

In order to clarify if "idiopathic" RPGN still exists as a distinct entity we reviewed 41 patients with histological picture of diffuse crescentic GN (60% of crescents) and no clinical evidence of systemic disease. According to the presence or absence of intraglomerular necrotizing lesions we subdivided the patients into two different morphological groups: Group I (25 pts) with necrotizing GN and massive periglomerular infiltrates; Group II (16 pts) with intra-extracapillary proliferation and no interstitial infiltrates. Our data suggest that "idiopathic" RPGN does not exist as a distinct entity, but is an expression either of renal limited vasculitis or crescentic GN complicating primary proliferative GN.