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What exactly is Peyer's Patch?

Peyer's patch are just part of the normal structure of the small intestine. It's part of the lymphoid system. What specifically does the pathology report say about them.

The clogging or inflammation of the lymph ducts/peyer's patches is gaining some interest again as a possible etiology of Crohn's disease. You can Google granulatomous lymphangitis, or search this site, to read about it.
Kiny is a member here that can give you some great info on peyer's patches and their involvement in CD.

It's a common find in scopes that peyer's patches are inflamed with CD in the terminal ileum.

Hopefully by me tagging Kiny they will be by to comment.


Well-known member
San Diego
The lymphoid system a major part of the immune system that is a sort of diffuse and extensive system of several different types of white blood cells. The white blood cells (WBCs) constantly circulate in the blood and lymphatics, but they also congregate in certain structures whose function is to filter out and trap foreign invaders and provide a point of focus for the WBCs to come in contact with the foreign cells, become activated, proliferate, and attack them.

The major organs of the body that comprise the lymphoid system are primarily the spleen, liver (especially in fetuses), and the thymus. But in addition there are many smaller outposts of the lymphoid system scattered throughout the body: the tonsils, the lymph nodes, and in the gut Peyer's patches, and others. So like other lymphoid organs Peyer's patches serve as a physical and functional focal point for the immune response. So it makes sense that for a disease like Crohn's that is characterized by an over-activity of the immune response in the gut, Peyer's patches are likely to be involved in some way.
I believe it is a histology term for a CD finding.

Histology is the science of tissue analysis and pathology.

In contrast, UC (ulcerative colitis) features things like crypt architecture, changes in goblet cells, etc.

They are just science terms for what the tissue lab sees in the biopsies. Each disease has its own features which are repeatedly seen in people who have these particular diseases.
The terminal ileum is the section of bowel where the large and small bowel meet. Terminal ileum problems are a feature of CD.

Terminal ileitis usually doesn't show up in a condition such as UC, unless it is 'backwash ileitis' (often part of Pancolitis).

A healthy terminal ileum (TI) is important because vitamins such as B12, etc are absorbed there. An impaired TI is not doing that job.

This is why CD folks may need to get Vitamin B12 shots, etc.


Well-known member
Haven't been on a lot, saw tag late.

Peyer's patches are normal to begin with, it's just a feature of the small intestine, it is the inflammation of them that is a sign of an issue.

Peyer's patches are tissue with immune cells. They're only found in the small intestine, you can see them with the naked eye through an endoscope, they look like little domes. The little dome bump is caused by the immune cells, the follicle. They're right on the surface of the intestinal wall, covered by M cells. I posted pictures of inflamed peyer's patches before. Peyer is from the person who discovered them, patches is because they're spread out like a patch. They're like mini lymph nodes in a way. Most people learn about lymph nodes long before they hear about peyer's patches so it's common to compare them to a lymph node.

Peyer's patches are like sensors, they're like the guards of the small intestine checking if everyone who is present in the small intestine is allowed to be there. If peyer's patches is the police station of the small intestine, then M cells are the gate that opens and closes. M cells are right on the surface, they actually aren't covered with mucus, and the guards at the M cells call in thousands of particles and antigens in to check for questioning in the peyer's patch.

The peyer's patch is filled with lymphocytes and dendritic cells. The immune system consists of the innate immune system and adaptive immune system. Dendritic cells awaken the adaptive immune cells if something has gone wrong (such as a salmonella infection), it's the alarm bell that will awaken those lymphocytes (B and T cells). They're often called antigen presenting cells, APC, since they present antigen to immune cells from the adaptive immune system as evidence that something is going horribly wrong in the body and they need new recruits to help, they're the alarm bell. Not only that, since those peyer's patches are conected to the lymphatic system, it will start recruiting more and more immune cells until the threat is over.

Anyway, why the peyer's patches are interesting in crohn's disease. Is because they are specific to the small intestine, if inflamed they are the first signs with an endoscope of crohn's disease, they are most active during teen years (crohn's is most diagnosed during those years) and we know AIEC invades peyer's patches through those M cells (AIEC is associated with crohn's disease).
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