Rare renal pathologic manifestation of antineutrophil cytoplasmic antibodies associated vasculitis as suppurative interstitial nephritis: A case report and review of the literature.

A 69-year old male patient attended our clinic with fatigue, fever, anuria, nephritic syndrome and severe renal failure. Kidney biopsy showed pauci-immune crescentic glomerulonephritis with an unusual association of suppurative interstitial nephritis. Though most patients with renal involvement linked to antineutrophil cytoplasmic antibodies associated vasculitis (AAV) have pauci-immune glomerulonephritis, only a few patients were identified to have atypical renal pathology. In most cases, mononuclear tubulointerstitial infiltrate may be a feature of AAV, suppurative interstitial nephritis is very rare. In the literature, we found only one case reported associated with suppurative interstitial nephritis without glomerulonephritis who later developed classic pauci-immune necrotizing glomerulonephritis. Here, we report a case diagnosed as AAV, presenting with pauci-immune crescentic glomerulonephritis and suppurative interstitial nephritis. It is not clear whether suppurative interstitial nephritis is a severe disease variant in AAV-associated renal disease. As described in the first case the lack of improvement in renal functions in spite of intense immunosuppressive treatment leads to the conclusion that suppurative interstitial nephritis is a marker of poor prognosis.