Systemic

Crohn’s disease, like many other chronic, inflammatory diseases, can cause a variety of systemic symptoms. Among children, growth failure is common. Many children are first diagnosed with Crohn’s disease based on inability to maintain growth. As it may manifest at the time of the growth spurt in puberty, up to 30% of children with Crohn’s disease may have retardation of growth.

Fever may also be present, though fevers greater than 38.5 ˚C (101.3 ˚F) are uncommon unless there is a complication such as an abscess. Among older individuals, Crohn’s disease may manifest as weight loss, usually related to decreased food intake, since individuals with intestinal symptoms from Crohn’s disease often feel better when they do not eat and might lose their appetite. People with extensive small intestine disease may also have malabsorption of carbohydrates or lipids, which can further exacerbate weight loss.

Extraintestinal

In addition to systemic and gastrointestinal involvement, Crohn’s disease can affect many other organ systems. Inflammation of the interior portion of the eye, known as Uveitis, can cause eye pain, especially when exposed to light. Inflammation may also involve the white part of the eye (sclera), a condition called Episcleritis. Both Episcleritis and Uveitis can lead to loss of vision if untreated.

Crohn’s disease is associated with a type of rheumatologic disease known as Seronegative Spondyloarthropathy. This group of diseases is characterized by inflammation of one or more joints (Arthritis) or muscle insertions (Enthesitis). The arthritis can affect larger joints, such as the knee or shoulder, or may exclusively involve the small joints of the hands and feet. The arthritis may also involve the spine, leading to Ankylosing Spondylitis if the entire spine is involved or simply Sacroiliitis if only the lower spine is involved. The symptoms of arthritis include painful, warm, swollen, stiff joints and loss of joint mobility or function.

Crohn’s disease may also involve the skin, blood, and endocrine system. One type of skin manifestation, Erythema nodosum, presents as red nodules usually appearing on the shins. Another skin lesion, Pyoderma gangrenosum, is typically a painful ulcerating nodule.

Crohn’s disease also increases the risk of blood clots; painful swelling of the lower legs can be a sign of deep venous thrombosis, while difficulty breathing may be a result of pulmonary embolism. Autoimmune hemolytic anemia, a condition in which the immune system attacks the red blood cells, is also more common in Crohn’s disease and may cause fatigue, pallor, and other symptoms common in anemia. Clubbing, a deformity of the ends of the fingers, may also be a result of Crohn’s disease. Crohn’s disease may cause Osteoporosis (thinning of the bones). Individuals with osteoporosis are at increased risk of bone fractures.

Crohn’s disease can also cause neurological complications (reportedly in up to 15% of patients). The most common of these are seizures, stroke, myopathy, peripheral neuropathy, headache and depression.

Crohn’s patients often also have issues with small bowel bacterial overgrowth syndrome, which has similar symptoms.

In the oral cavity crohn’s patients may suffer from Cheilitis granulomatosa and other forms of orofacial Granulomatosis, Pyostomatitis vegetans, recurrent Aphthous stomatitis, geographic tongue and migratory Stomatitis in higher prevalence than the general population.

Complications

Crohn’s disease can lead to several mechanical complications within the intestines, including obstruction, fistulae, and abscesses. Obstruction typically occurs from strictures or adhesions that narrow the lumen, blocking the passage of the intestinal contents. Fistulae can develop between two loops of bowel, between the bowel and bladder, between the bowel and vagina, and between the bowel and skin. Abscesses are walled off collections of infection, which can occur in the abdomen or in the perianal area in Crohn’s disease sufferers.

Crohn’s disease also increases the risk of cancer in the area of inflammation. Individuals with Crohn’s disease involving the small bowel are at higher risk for small intestinal cancer. Similarly, people with Crohn’s colitis have a relative risk of 5.6 for developing colon cancer.

Individuals with Crohn’s disease are at risk of malnutrition for many reasons, including decreased food intake and malabsorption. The risk increases following resection of the small bowel. Such individuals may require oral supplements to increase their caloric intake, or in severe cases, total parenteral nutrition (TPN).

Crohn’s disease can cause significant complications, including bowel obstruction, abscesses, free perforation and hemorrhage.

Crohn’s disease can be problematic during pregnancy, and some medications can cause adverse outcomes for the fetus or mother. In some cases, remission can occur during pregnancy. Certain medications can also impact sperm count or may otherwise adversely affect a man’s ability to conceive.

Cause

Crohn’s disease seems to be caused by a combination of environmental factors and genetic predisposition. Researchers believe that in Crohn’s disease the immune system attacks bacteria, foods, and other substances that are actually harmless or beneficial. During this process, white blood cells accumulate in the lining of the intestines, producing chronic inflammation, which leads to ulcers, or sores, and injury to the intestines.

Researchers have found that high levels of a protein produced by the immune system, called tumor necrosis factor (TNF), are present in people with Crohn’s disease. However, researchers do not know whether increased levels of TNF and abnormal functioning of the immune system are causes or results of Crohn’s disease. Research shows that the inflammation seen in the GI tract of people with Crohn’s disease involves several factors: the genes the person has inherited, the person’s immune system, and the environment.

The increased incidence of Crohn’s in the industrialized world indicates an environmental component. Crohn’s is associated with an increased intake of animal protein, milk protein and an increased ratio of omega-6 to omega-3 polyunsaturated fatty acids. Those who consume vegetable proteins appear to have a lower incidence of Crohn’s disease. Smoking increases the risk of the return of active disease (flares). The introduction of hormonal contraception in the United States in the 1960s is associated with a dramatic increase in incidence, and one hypothesis is that these drugs work on the digestive system in ways similar to smoking. Emotional stress is likely to exacerbate Crohn’s.