Steroid-responsive renal insufficiency due to idiopathic granulomatous tubulointerstitial nephritis

A 26-year-old male was admitted to our hospital having suffered from subfever, sterile pyuria and renal insufficiency for 1 year. There had been no apparent hematuria/proteinuria, and evidence of infection, allergy or intoxication was not demonstrated. Open renal biopsy revealed severe tubulointerstitial changes with granuloma accompanied by neither caseous necrosis nor giant cells. Infiltrating cells mostly consisted of CD4 and CD8 T cells, and some proximal tubular cells presented MHC class II antigen. Following the negative culture of biopsied specimen for acid-fast bacilli, diagnosis of idiopathic granulomatous tubulointerstitial nephritis was made, and steroid therapy was started. Two months later, pyuria disappeared and renal function improved significantly, proving the effectiveness of steroid on idiopathic granulomatous tubulointerstitial nephritis.