Which part of the gastrointestinal tract is primarily affected in Crohn's disease, leading to potential pernicious anemia?

In Crohn's disease, the ileum, which is the last part of the small intestine, is primarily affected. This condition is characterized by chronic inflammation that can lead to various complications, including nutritional deficiencies.

Pernicious anemia specifically arises when there is an impaired absorption of vitamin B12, which is crucial for the production of red blood cells and is predominantly absorbed in the ileum. The inflammation and damage to the ileal mucosa in Crohn's disease can disrupt the absorption of vitamin B12, leading to a deficiency that results in pernicious anemia.

The other parts of the gastrointestinal tract—such as the stomach, colon, and duodenum—may have some involvement in Crohn's disease, but they do not play the same critical role in vitamin B12 absorption as the ileum does.