A case of idiopathic granulomatous interstitial nephritis with an unusually large granuloma.

Granulomatous interstitial nephritis (GIN) is a rare disease. Contributing factors such as drugs, sarcoidosis, infections, and paraproteinemia have been reported, and when no obvious contributing factors can be identified, the disease is classified as idiopathic GIN. We managed a patient with idiopathic GIN with an unusually large granuloma. Usually, granulomas are smaller or slightly larger than glomeruli. However, our patient had an atypical granuloma, and such a large granuloma has never been reported. GIN can be treated with steroids, and our patient improved after high-dose steroid treatment.