The following information may help to address your question:
How many people in the United States have Crohn's disease?
Crohn's disease may affect as many as 700,000 people in the U.S. Men and women are affected in equal numbers. While the condition can occur at any age, it is more common among adolescents and young adults between the ages of 15 and 35.
Last updated: 3/15/2016
How is Crohn's disease diagnosed?
A variety of tests are used to diagnose and monitor Crohn’s disease. A combination of tests is often needed because some symptoms of the condition are similar to other intestinal disorders such as irritable bowel syndrome
and to another type of inflammatory bowel disease
(IBD) called ulcerative colitis
Tests used to narrow down the diagnosis may include blood tests, tissue tests, ultrasound, x-rays, CT scan, and/or endoscopy. A proper diagnosis also involves identifying the extent and severity of disease as well as any related complications.
Last updated: 10/15/2012
What is Crohn's disease?
is a type of inflammatory bowel disease (IBD)
, the general name for conditions that cause inflammation in the gastrointestinal (GI) tract. Common signs and symptoms include abdominal pain and cramping, diarrhea, and weight loss. Other general symptoms include feeling tired, nausea and loss of appetite, fever, and anemia
. Complications of Crohn's disease may include intestinal blockage, fistulas
, anal fissures
, ulcers, malnutrition, and inflammation in other areas of the body. Crohn's disease can occur in people of all age groups but is most often diagnosed in young adults. The exact cause is unknown, but is thought to involve both genetic and environmental factors. It appears to run in some families. Treatment is aimed at relieving symptoms and reducing inflammation, but some people require surgery.
Last updated: 3/15/2016
What are the signs and symptoms of Crohn's disease?
Crohn's disease causes inflammation of the digestive or gastrointestinal (GI) tract. It usually occurs in the lower part of the small intestine
, called the ileum, but it can affect any part of the digestive tract, from the mouth to the anus. The inflammation extends deep into the lining of the affected organ, which can cause abdominal pain and diarrhea.
Affected individuals may also have loss of appetite, weight loss, and fever.
About one-third of individuals with Crohn's disease have symptoms outside of the intestines, which may include arthritis, uveitis (inflammation of the covering of the eye), skin lesions, and sacroilitis (inflammation of the large joints of the tail bone and pelvis).
Symptoms of Crohn's disease may range from mild to severe. Most people will go through periods in which the disease flares up and causes symptoms, alternating with periods when symptoms disappear or decrease. People with Crohn’s disease who smoke tend to have more severe symptoms and more complications. In general, people with Crohn's disease lead active and productive lives.
Last updated: 11/15/2012
What causes Crohn's disease?
The exact cause of Crohn's disease is not known, but it appears to be a multifactorial condition. This means that both genetic and environmental factors likely interact to predispose an individual to being affected. Studies suggest that Crohn's disease may result from a combination of certain genetic variations, changes in the immune system, and the presence of bacteria in the digestive tract.
Recent studies have found that variations in specific genes, including the ATG16L1
, and NOD2
genes, influence the risk of developing Crohn's disease. These genes provide instructions for making proteins that are involved in immune system function. Variations in any of these genes may disrupt the ability of intestinal cells to respond to bacteria, leading to chronic inflammation and thus the signs and symptoms of the condition. There may also be genetic variations in regions of chromosome 5
and chromosome 10
that contribute to an increased risk to develop Crohn's disease.
Last updated: 10/15/2012
Is Crohn's disease inherited?
Crohn's disease, like most other autoimmune diseases
, is thought to be a multifactorial condition
. This means it is likely associated with the effects of multiple genes, in combination with lifestyle and environmental factors.
Once an autoimmune disease is present in a family, other relatives may be at risk to develop the same autoimmune disease, or a different autoimmune disease. However, if an autoimmune diseases such as Crohn's disease occurs in a family, it does not necessarily mean that relatives will develop an autoimmune disease.
Having an affected family member means that there may be a genetic predisposition
in the family that could increase an individual's chance of developing an autoimmune disease. Thus, having an affected family member is considered a risk factor for Crohn's disease.
Last updated: 10/15/2012
What is the chance of a child developing Crohn's disease if a parent is affected by this condition?
Studies have shown that if one parent has this disease, each of his/her children has up to a 10% chance of developing the disease; if both parents have the disease, each of their children has up to a 50% chance of developing the disease. 
Last updated: 2/8/2012
What genes are currently known to be associated with Crohn's disease?
More than 30 distinct genes
, or presumed locations of genes (loci
), have been suggested to be related to CD, including those related to susceptibility, age of onset, disease location, diagnosis, and prognosis.
So far, the strongest associations with CD have been found with the NOD2
(also called CARD15
The search for specific susceptibility genes (genes in which variations may increase a person's risk) has been difficult due to complex genetics, including factors such as the lack of simple inheritance patterns and involvement of several genes. Studies have already led to the identification of a number of susceptibility genes: NOD2, DLG5, OCTN1
(also called SLC22A4
), NOD1, IL23R, PTGER4, ATG16L1
. The NOD2
gene is currently the most replicated and understood.
With respect to age of CD onset and more specifically to childhood or early-onset Crohn’s disease, the following genes/loci have been implicated: TNFRSF6B, CXCL9, IL23R, NOD2
, ATG16L1 rs2241880, CNR1, IL-10
, and MDR1
(also called ABCB1
In terms of genes related to CD location, studies have suggested that upper GI Crohn’s disease has been related to NOD2
variants. Ileal CD has been related to the IL-10
, NOD2, ZNF365
genes. Genes/loci associated with ileocolonic CD are 3p21, ATG16L1
Variations in a number of genes have also been found to be associated with other aspects of CD, such as disease behavior, risk for cancer, and presence of extraintestinal manifestations.
To view a free, full-text journal article published in 2012 about the role of genetics in CD, click here
. To view only a table from this article listing the genes that appear to be associated with Crohn's disease, click here
Because the information provided here is complex, individuals seeking to better understand this information may benefit from meeting with a genetics professional or other qualified health care provider.
Last updated: 10/16/2012
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