Background: Renal disease in sarcoidosis may occur due to granulomatous interstitial nephritis. However, granulomatous interstitial nephritis in the absence of features of extrarenal sarcoid, or other causes, has been reported very rarely. In this report we describe seven such patients.
Methods: Since 1995, we have identified a number of patients with biopsy-proven granulomatous interstitial nephritis. Patients were excluded if they had (i) evidence of extrarenal sarcoid, (ii) infections that may have contributed to pathogenesis or (iii) an obvious drug-related aetiology.
Results: Seven patients were identified, of whom five were male and two female, with a median age of 69. Median calculated creatinine clearance at presentation was 14 ml/min. Two had raised serum calcium at presentation and three had a raised serum angiotensin-converting enzyme. All patients were treated with steroids and five out of seven had an improvement in their renal function. Two patients progressed to end-stage renal failure despite treatment with steroids.
Conclusions: Idiopathic granulomatous interstitial nephritis may represent a renal-limited form of sarcoid. It may be associated with hypercalcaemia and a raised serum angiotensin-converting enzyme and usually responds to treatment with corticosteroids.