<prompt> Which of the following is NOT associated with Crohns disease:Skip lesionsFistulaToxic megacolonTransmural involvement  <response>: Ans. c Toxic megacolonRef. Harrisons 17th ed. Ch. 289 Crohns disease is a chronic, recurrent disease characterized by patchy transmural inflammation involving any segment of the gastrointestinal tract from the mouth to the anus but most common site is Ileum. Crohns disease is one of the two main forms of Inflammatory bowel disease and is also known as Granulomatous colitis. Earliest manifestation is Apthous ulcers. Skip lesions, stricture formation, string sign of kantor is also seen. Hallmark feature of crohns is fistula formation. Cobble stone appearance is seen on X-Ray. NOTE: Toxic mega colon is seen in Crohns disease but most commonly toxic megacolon is seen in Ulcerative colitis. 