Crohn’s Disease Identified as Granulomatous Tubulointerstitial Nephritis

Crohn’s disease is usually diagnosed according to intestinal symptoms, but extra-intestinal manifestations are important in approximately one-third of cases. Although several extra-intestinal symptoms associated with various organs have been reported, renal involvement is uncommon in patients with Crohn’s disease. Tubulointerstitial nephritis in a patient with Crohn’s disease is usually caused by infection, sarcoidosis, or medications. However, primary tubulointerstitial nephritis caused by Crohn’s disease alone is extremely rare. A 19-year-old male patient was referred to our hospital because of an increase in serum creatinine level. He underwent a kidney biopsy with renal insufficiency. Renal histological findings revealed granulomatous tubulointerstitial nephritis. Thereafter, a colonoscopy was performed with suspicion of Crohn’s disease. Ultimately, he was diagnosed with granulomatous tubulointerstitial nephritis based on Crohn’s disease. The patient had improved gastrointestinal symptoms after the last treatment. This case report presents a rare case of primary tubulointerstitial nephritis caused by Crohn’s disease.