Crohn’s Disease

What is Crohn’s Disease?

Crohn’s disease is a chronic condition that causes inflammation of the digestive tract in which we see alternating periods of remissions and flares. It is a type of inflammatory bowel disease (IBD). IBD is a broad term currently encompassing the two similar gastrointestinal diseases, Crohn’s disease and ulcerative colitis (UC). Rarely, a diagnosis of indeterminate colitis (IC) will be given if a distinction between the two diseases cannot be made. Crohn’s is distinct from UC for a few important reasons: it is able to affect anywhere in the gastrointestinal (GI) tract, is transmural, and is characterized by discontinuous inflammation. While Crohn’s is able to affect anywhere in the GI tract, it most commonly occurs at the end of the small intestine and in the colon.

Figure 1: Anatomy of the lower portion of the gastrointestinal tract starting from the stomach. Ingested food is passed from the stomach to the small intestine and then through the large intestine.

As of 2011, it was estimated that there were about 780,000 Americans living with Crohn’s disease with approximately 33,000 new cases each year. There is no major difference in the number of men and women affected by Crohn’s. It is generally diagnosed in teenagers and young adults but can occur at any age.


The symptoms of Crohn’s and degree to which they are experienced varies based on the individual. It is also possible for symptoms to change over time. The most common are diarrhea, abdominal pain, rectal bleeding, loss of appetite, and weight loss. Some patients may experience fevers, fatigue, joint pain, mouth sores, and rashes.

Presenting with these symptoms for the first time will often prompt a gastroenterologist to suspect IBD and investigate further. An endoscopy is scheduled and performed to look for inflammation indicative of Crohn’s within the GI tract. Biopsies are taken to confirm the disease but the diagnosis is typically known from visual indications.


Unfortunately, the exact cause is not definitively known. There is known to be a genetic component. The disease runs in families but there is no guarantee siblings or children will develop it. Various mutations of genes, a common one being NOD2, have been identified but are not consistent throughout patients.

Environmental factors are believed to play a role in Crohn’s disease. Active smokers are more likely to develop Crohn’s and diet is also potentially involved. Some patients see aggravated symptoms from certain foods while others can eat anything. Antibiotics is a consideration for increased risk. It has been known for some time that patients with Crohn’s have an altered microbiota and, in many cases, dysbiosis. Newer research is starting to look more closely at the bacteria within the gut.


There is no cure and so the goal is to control inflammation and induce remission. Effectiveness of medications varies widely among patients and must be designed on an individual basis. Surgery is a last resort when treatment is ineffective but is by no means a cure. Nonetheless, a few categories of treatments are utilized for the disease. These categories are:

Aminosalicylates: This group of medication contains 5-aminosalicylic acid within the chemical structure of the drug. The medication is designed in such a way so that it releases within the intestines. Thus, it is effective at decreasing inflammation in the intestinal walls. These are usually not sufficient to maintain remission alone and require combination with another form of treatment.

Corticosteroids: These medications are powerful short term treatments for Crohn’s and many other conditions. They reduce inflammation by affecting the ability to start and maintain inflammatory processes. This class of medications is effective at controlling a flare-up and inducing remission in patients. However, the many side effects discourage prolonged use. Short term side effects include weight gain, infection, insomnia, and intense mood swings. Long-term use can lead to osteoporosis and cataracts later in life.

Immunomodulators: The medications within this group alter the immune system’s ability to function. They suppress the immune system and limit its ability to cause chronic inflammation. This means that it inhibits a patient’s ability to fight off pathogens and can result in certain infections leading to hospitalization. However, the immune system remains mostly intact so common infections can still be combatted, especially in younger patients who have a strong immune response. Immunomodulators are a common treatment to maintain remission and are often used on top of aminosalicylates.

Biological Therapies: This form of treatment is the most recently developed and is effective at managing patients with more severe Crohn’s disease. They are typically utilized when other methods proved ineffective due to being much stronger. They have an immunosuppressant effect like the immunomodulators but may be rejected by the body, leading to adverse reactions. The common treatments function by targeting tumor necrosis factor (TNF), an inflammatory protein, or by blocking certain white blood cells from entering the inflamed tissue.

A short timeline of important events pertaining to Crohn’s disease research.
Created in Adobe Spark.

Additional Information

The Crohn’s & Colitis Foundation of America covers the same information and a few more topics. Click here for the link to that document.

If you are interested in the finer details of the history, the molecular basis behind the disease, and an extensive list of references, visit the pages on my website by clicking here.

6 thoughts on “Crohn’s Disease

  1. So does this mean that since they understand the structure of the rabbit NOD2 protein that they are closer to finding a cure for this disease or a vaccine. Thanks for the information on Crohn’s.

    1. Thanks for the question! I believe it is definitely a big leap forward because this will allow us to better understand its function and the interactions that it makes. The hope is that researchers will be able to build off this recent work and at the very least improve treatments. It is difficult to say exactly how much closer to a cure we are because there is still so much unknown about the condition. Numerous specific mutations within NOD2 have been identified and no single change can be fully attributed to causing the condition as not every individual with Crohn’s disease has them. Based on research, there appear to be other factors at play that have yet to be identified. This provides a challenge when trying to find a cure for the disease. Some new research is starting to focus more on the bacteria within the intestines, so hopefully that will provide useful information regarding Crohn’s disease!

  2. Is there any data on how often Crohn’s disease is misdiagnosed due to it’s symptoms being similar to other gastrointestinal issues and diseases?

    1. Thank you for the great question! I was able to find a study, linked below if you’re interested, performed in the UK that looked at the chance of being diagnosed with irritable bowel syndrome (IBS) before inflammatory bowel disease (IBD). Although difficult to say whether it is a misdiagnosis, it could be seen as one especially if it delays an IBD diagnosis. These researchers found that patients were three times as likely to be diagnosed with or have therapy for IBS. It was also more likely in patients with Crohn’s disease compared to those with ulcerative colitis. As this study shows, gastrointestinal issues can certainly be challenging to diagnose and there is a real possibility of misdiagnosing patients.

  3. I read that diarrhea is one of the first symptoms of Crohn’s disease. If so, is it hard for doctors to diagnose the disease properly with a symptom like diarrhea being such a common symptom for a variety of sicknesses?

    1. Thank you for the question, Karen! Proper diagnosis of Crohn’s disease can be a difficulty faced by both patients and physicians. Anecdotally, I know of a few situations where the patient was initially diagnosed with ulcerative colitis and then later had that diagnosis changed to Crohn’s. This can be an issue because ulcerative colitis can be cured through surgery since it only affects the colon whereas Crohn’s disease has no cure. One of the reasons these misdiagnoses happen is because the conditions present with similar symptoms. Diarrhea, as you mention, can be caused by just about anything such as infections, medications, and of course gastrointestinal diseases. This means that misdiagnoses would occur if you rely on only a couple symptoms. This is why it usually takes more concerning symptoms like bleeding and weight loss combined with persistent diarrhea to indicate Crohn’s disease. On top of that, physicians will look inside the GI tract via an endoscopy to see inflammation and take samples that are sent to a lab. The lab will run tests to rule out other causes such as a bacterial infection and look for microscopic signs that are seen with Crohn’s disease.

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