**Core Concept**
Crohn's disease is a type of inflammatory bowel disease (IBD) characterized by chronic inflammation of the gastrointestinal tract, leading to symptoms such as abdominal pain, diarrhea, weight loss, and fatigue. The exact cause of Crohn's disease is unknown, but it is believed to result from a combination of genetic, environmental, and immune system factors.

**Why the Correct Answer is Right**
Crohn's disease is a transmural disease, meaning it affects all layers of the gastrointestinal tract, from the mucosa to the serosa. The inflammation in Crohn's disease can lead to complications such as narrowing of the intestine (stricture), fistula formation, and abscesses. The disease is often associated with an abnormal immune response to certain bacteria, such as Escherichia coli, and an imbalance of gut microbiota.

**Why Each Wrong Option is Incorrect**
**Option A:** Crohn's disease is a type of irritable bowel syndrome (IBS). _Incorrect because IBS is a functional disorder, whereas Crohn's disease is a chronic inflammatory condition._
**Option B:** Crohn's disease is caused by a viral infection. _Incorrect because the etiology of Crohn's disease is multifactorial, involving genetic, environmental, and immune system factors._
**Option C:** Crohn's disease is characterized by a predominantly eosinophilic infiltrate. _Incorrect because Crohn's disease is characterized by a predominantly neutrophilic infiltrate, with lymphocytes and macrophages also present._

**Clinical Pearl / High-Yield Fact**
It's essential to distinguish Crohn's disease from ulcerative colitis, another type of IBD, as the treatment and prognosis differ between the two conditions. Crohn's disease often requires a multidisciplinary approach, involving gastroenterologists, surgeons, and other specialists.

**Correct Answer:** D.