Crohn's disease (CD)

Crohn's disease (CD) is a chronic inflammatory bowel disease. It can affect any part of the GI tract from the oral cavity to the perianal area. The cause is so far unclear. If untreated, it can reduce life quality and leads to significant organ damage. Modern strategies aim to:

* Alter disease progression early.
* Prevent bowel damage.
* Not just alleviate symptoms.
* 

The disease is characterized by relapsing episodes (1, 2, 3, 4).

Crohn's Disease (CD) involves segmental transmural inflammation of the intestinal mucosa. This inflammation can occur anywhere in the gastrointestinal tract. The ileum is most frequently affected (5). The ypical clinical scenario is:

• Abdominal pain,


• Chronic diarrhea,


• weight loss, and


• fatigue (6).

CD284 (Toll-Like Receptor 4 (TLR-4)) and Toll-like receptor 9 (TLR-9) are highly expressed in Crohn’s disease and ulcerative colitis compared to healthy controls. These receptors are found in DCs (Dendritic Cells) (7). And CD was previously linked with chronic Th1 immunity (8). Moreover, IL-23 and CD4+ Th17 cells are involved. Mouse studies showed significant participation of these cells in intestinal inflammation (9, 10, 11).

Genome-wide association studies (GWAS) have identified genetic susceptibility loci linked to CD, including card15/nod2 gene, card9 gene, atg16l1 gene, irgm gene, and fut2 gene. These genes are linked to the abundance of specific bacteria (12). Mutation in the card15/nod2 gene has been associated with a higher risk of Crohn's disease (CD) (13).

References

(1) Rubin et al. 2025 Inflammatory Bowel Diseases 31(8): 2269-2285
(2) Dell’Avalle et al. 2022 Expert Opin. Investig. Drugs 31: 145-161
(3) Olaisen et al. 2021
(4) Wu & Shen 2020 Front. Immunol. 11: 554880
(5) Baumgart & Sandborn 2007 Lancet 18: 379-87
(6) Torres et al. 2017 Lancet North Am Ed 389(10080): 1741-55
(7) Ghavami et al. 2020
(8) Abraham & Cho 2009a N. Engl. J. Med. 361: 2066-2078
(9) Cua et al. 2003 Nature 421(6924): 744-8
(10) Langrish et al. 2005 J Exp Med 201(2): 233-40
(11) Maloy & Kullberg 2008 Mucosal Immunol 1(5): 339-49
(12) Gong et al. 2026 Front Microbiol 17: 1856205
(13) Hugot et al. 2001 Nature 411: 599-603

see also:
Inflammatory Bowel Disease (IBD)
Pediatric Inflammatory Bowel Disease (IBD)