True statement regarding Hirschsprung’s disease-
**Core Concept**
Hirschsprung's disease is a congenital condition characterized by the absence of ganglion cells in the distal colon and rectum, leading to a functional obstruction. This absence of ganglion cells results in an accumulation of stool behind the affected segment, causing intestinal obstruction.
**Why the Correct Answer is Right**
In Hirschsprung's disease, the absence of ganglion cells is due to the failure of neural crest cells to migrate to the distal colon and rectum during embryonic development. This results in a segment of the colon that is non-peristaltic and unable to relax, leading to a functional obstruction. The affected segment is characterized by the presence of a thickened, fibrotic muscle layer and an increase in the number of submucosal nerve fibers, but the absence of enteric nervous system ganglion cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Hirschsprung's disease is not caused by a genetic mutation affecting the colon's muscular layer.
**Option B:** This option is incorrect because the condition is not related to a viral infection causing inflammation of the colon.
**Option C:** This option is incorrect because the disease is not characterized by an overactive enteric nervous system.
**Clinical Pearl / High-Yield Fact**
The "aganglionosis" seen in Hirschsprung's disease can be detected by rectal biopsy, which shows the absence of submucosal and myenteric ganglion cells.
**Correct Answer: . The disease is characterized by the absence of ganglion cells in the distal colon and rectum.**