Diffuse tubulointerstitial nephritis associated with ANCA-negative pauci-immune glomerulonephritis.

Tubulointerstitial nephritis (TIN) is histopathologically characterized by the infiltration of leukocytes, edema, and fibrosis of the renal interstitium with or without tubulitis and vasculitis. TIN is not usually accompanied by specific glomerular lesions. We herein report the case of a 65-year-old male with a diagnosis of non-small cell lung carcinoma that showed acute renal failure, together with proteinuria and microscopic hematuria. The renal biopsy findings showed severe and diffuse TIN, despite the fact that glomerulonephritis (GN) with cellular crescents was only focally identified. In this case, the GN was of the pauci-immune type, but the serum tests for anti-neutrophil cytoplasmic antibodies were negative. No disorders known to be associated with TIN were detected. The pathogenesis involved in this unusual presentation of a concomitant occurrence of TIN and pauci-immune GN is currently unclear.