This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Pathology
[{'content': "Total colonic aganglionosis is a variant of? \nSelect and explain. \nA. Crohn's disease, B. Ulcerative colitis, C. Hirschsprung's disease, D. Tropical sprue", 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Hirschsprung's disease * Hirschprung disease (Congenital aganglonic megacolon) is caused by defective migration of neural crest into the mesodermal layer of gut. There is aganglionosis (absence of ganglions) in a portion of intestinal tract. Intestinal segment lacks both Meissner submucosal and Auerbach myenteric plexuses.* Total colonic aganglionosis (Zuelzer Wilson syndrome) is particular variant of Hirschsprung's disease (5-8% cases) in which aganglionic portion extends to entire length of colon. In rare cases aganglionosis may extent from duodenum to rectum.", 'role': 'assistant'}]