Crohn’s disease

Crohn’s disease is a chronic, or long-lasting, condition in which the immune system causes inflammation in the digestive tract. It most often affects the small intestine and the start of the large intestine, but it can affect any part from the mouth to the anus. It is one type of inflammatory bowel disease, or IBD.

Symptoms often come and go. A time with symptoms is called a flare, and a calmer time is called remission, which can last for weeks or years. Doctors diagnose Crohn’s disease with blood and stool tests, scans and endoscopy, which uses a thin tube with a camera to look inside the gut and take small tissue samples.

Doctors do not know exactly what causes Crohn’s disease. One likely cause is an immune system that reacts wrongly to bacteria that normally live in the gut. Genes, a person’s surroundings and the mix of microbes in the gut, called the microbiome, all seem to play a part.

Crohn’s disease sometimes runs in families. Having a parent, brother or sister with it raises the chance of getting it, and smoking may about double the chance. It can start at any age, but the US National Institutes of Health says people aged 20 to 29 are more likely to develop it.

The most common symptoms are diarrhea, cramping and belly pain, and weight loss. Some people also feel very tired or have fever, nausea or anemia, which means too few red blood cells. Inflammation can also affect the joints, eyes, skin or liver.

Over time, inflammation can cause serious problems. These include a blocked bowel, fistulas (tunnels that form between the gut and another organ or the skin), abscesses (pockets of infection) and tears or sores around the anus. Children may grow more slowly or start puberty late.

Long-standing Crohn’s disease in the large intestine raises the risk of colorectal cancer. For that reason, doctors often recommend regular colonoscopy checks, most often starting 8 to 10 years after diagnosis.

Crohn’s disease is usually lifelong, with flares and calmer times. Regular visits help the care team adjust treatment and watch for problems such as anemia, poor nutrition and bone thinning, which can come from the disease or from steroids. Many people with Crohn’s disease also report stress, depression or anxiety, and stress may make symptoms worse.

European bowel disease and transplant experts (ECCO and EBMT) say a transplant should be done only at experienced centers with both transplant and bowel specialists. Where possible, it should be part of a clinical trial. The process includes collecting stem cells, a hospital stay for high-dose treatment and a recovery period with a high risk of infection.

Transplant is not a reset that ends Crohn’s disease for most people. In a registry study of 82 people treated at 19 centers in seven European countries, reported in 2018, about two-thirds improved a lot or went into remission, but most needed Crohn’s medicines again at some point. Some of them then responded to medicines that had stopped working before.

Crohn’s disease is not usually treated with a donor transplant. When a stem cell transplant is used, it is autologous, which means it uses the person’s own stem cells, collected before treatment. No registry donor is involved, and no donor search is needed.

In their 2025 recommendations, European transplant experts (EBMT) said an own-cell transplant can be considered for carefully selected people after careful weighing of risks and benefits. For adults, they listed donor transplants for Crohn’s disease as developmental, meaning more research is needed.

A separate and very rare situation affects some babies and young children. Severe bowel inflammation caused by a single inherited immune gene change, such as interleukin-10 receptor deficiency, can look like Crohn’s disease. These are inherited immune disorders, and European experts say a donor stem cell transplant is appropriate for them. For most people living with Crohn’s disease, though, joining a donor registry is a way to help other patients rather than a need of their own.