Snapshot A 18-year-old boy presents to his primary care physician for abdominal pain, diarrhea, and chronic fatigue. He reports that he has nonbloody diarrhea for the past few weeks. He could not identify any “bad” foods, and nobody else around him has the same symptoms. His aunt has a history of inflammatory bowel disease, but he is unsure which specific disease. He is noted to be underweight on physical exam. Laboratory results show elevated erythrocyte sedimentation rate (ESR) and C-reactive protein. He is scheduled for a colonoscopy with biopsy to confirm the diagnosis. Introduction Overview Crohn disease is an inflammatory bowel disease that can affect any part of the gastrointestinal (GI) tract, including the mouth and the anus characterized by abdominal pain and nonbloody diarrhea classically associated with non-contiguous involvement, or “skip lesions”, along GI tract Epidemiology demographics onset 15-30 years of age or 60-70s years of age risk factors family history Pathogenesis mechanism chronic Th1-mediated inflammation starts as focal inflammatory infiltrates around crypts, evolves into transmural inflammation and noncaseating granulomas Prognosis unpredictable course of relapses and remissions Presentation Symptoms GI symptoms results from transmural involvement abdominal pain bloody or nonbloody diarrhea abscess fistulas strictures malnutrition extraintestinal manifestations arthralgias kidney stones calcium oxalate ankylosing spondylitis gallstones due to poor bile acid absorption at the ileum systemic symptoms chronic intermittent fever weight loss fatigue Physical exam skin and mucosal findings pyoderma gangrenosum erythema nodosum aphthous stomatitis perianal region skin tags scarring ocular finding episcleritis uveitis Imaging Abdominal radiograph indications assess for bowel obstruction CT of abdomen indications evaluation for obstruction, fistulas, or abscesses Studies Serum labs serology used when endoscopic studies and barium studies are inconclusive anti-saccharomyces cerevisiae positive anti-neutrophil cytoplasmic antibody negative complete blood cell count elevated inflammatory markers Invasive studies colonoscopy or esophagogastroduodenoscopy indication diagnostic findings cobblestone mucosa skip lesions bowel wall thickening ulcers fissures Histology noncaseating granulomas lymphoid aggregates Differential Ulcerative colitis key distinguishing factors bloody diarrhea disease affecting colon and always the rectum mucosal and submucosal inflammation only Treatment Medical 5-aminosalicylic acid agents indications mild disease initial therapy drugs mesalamine best initial therapy sulfasalazine corticosteroids indications for flares immunosuppressive agents drugs infliximab / adaliumumab good for those with fistula formation necessary for disease remission antibodies targeted against tumor necrosis factor alpha azathioprine recurrent symptoms off steroids antibiotics drugs metronidazole/ciprofloxacin perianal involvement anti-diarrheal medications drugs loperamide Surgical surgical resection of affected area indications not curative Complications Fistula formation Colorectal cancer Abscesses Strictures