Tubulointerstitial nephritis as an extraintestinal manifestation of Crohn's disease

Background: A 12-year-old boy presented to hospital with a 6-month history of crampy pre-defecation abdominal pain, non-bloody diarrhea, anorexia and weight loss. Investigations revealed hypochromic microcytic anemia, a low serum iron level, a low serum ferritin level and an elevated serum creatinine level. Histopathological examination of tissue specimens obtained at esophagogastroduodenoscopy and colonoscopy revealed features of Crohn's disease, and a renal biopsy demonstrated tubulointerstitial nephritis. A second case of tubulointerstitial nephritis in a patient with Crohn's disease, is also presented. Investigations: Physical examination, laboratory tests including full blood count, electrolytes, renal function, serum albumin, urinalysis and 24 h urinary protein, esophagogastroduodenoscopy, colonoscopy, abdominal ultrasonography, dimercaptosuccinic acid scan, renal diethylene triamine pentaacetic acid clearance study and renal biopsy. Diagnosis: Tubulointerstitial nephritis secondary to Crohn's disease. Management: Prednisone therapy (60 mg/day) for 1 month followed by a tapering schedule over 3 months.