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
Total colonic aganglionosis is a variant of? 
Select and explain. 
A. Crohn's disease, B. Ulcerative colitis, C. Hirschsprung's disease, D. Tropical sprue
C: Hirschsprung's disease
Answer: C: Hirschsprung's disease 
Explanation: 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.