[Granulomatous interstitial nephritis: A retrospective study of 44 cases].

Purpose: Granulomatous interstitial nephritis (GIN) are identified in 0.5 to 1,3% of all renal biopsies. Renal outcome and treatment modalities are not clearly established in the literature.

Methods: We retrospectively analyzed a case series of 44 GIN identified among all renal biopsies performed between 1984 and 2005 in the Rhône-Alpes area.

Results: The study population included 25 men and 19 women with a mean age of 56 years, and mean diagnostic delay was 11 months. Renal function was severely impaired (mean creatinine clearance 24mL/min). Proteinuria was observed in 77% (mean value 0,9 g/24h) of the patients and associated with microscopic hematuria and leukocyturia in 30% and 25%, respectively. The most common diagnosis was sarcoidosis (25%, n = 11), followed by drug-induced GIN (9%, n = 4), tuberculosis (6,8%, n=3), hemopathy-related paraneoplastic GIN (6,8%, n = 3), HIV infection (n = 1) and chronic renal allograft rejection (n = 1). In other patients, no aetiology was found (48%, n = 21). Severity of renal failure justified hemodialysis in 34% (n = 15) of the patients. Three patients underwent renal transplantation. Nonetheless, renal outcome was generally favorable: renal function improved in 41% (n = 18) and stabilized in 34% (n = 15) of patients.

Conclusions: Sarcoidosis, drug-induced and infections represent the main causes of GIN. Histologic features are not specific enough to determine the aetiology. Corticosteroids is the gold standard in sarcoidosis, drug-induced, and idiopathic GIN. Treatment is etiologic in the other cases.