Coeliac disease

Coeliac disease is a condition in which the inner lining of the small intestine is damaged leading to a defect in the absorption of nutrients. The normal structure of the inner surface of the small intestine lining, is composed of undulating wavy projections that are called villi. These help increasing the surface area of the intestine for effective absorption of nutrients.

In coeliac disease the patients are intolerant to a protein in gluten, which is found in wheat, rye, barley and oats. In such patients, when gluten is ingested the immune system overreacts and responds by attacking the cells lining the small intestine leading to a destruction of the villi. As a result nutrients are unable to be absorbed and malnutrition ensues regardless of the quality or quantity of food consumed.

Coeliac disease is also known as coeliac sprue, non-tropical sprue and gluten-sensitive enteropathy. It was originally believed to be a disease of the gastrointestinal system, but in recent years has been classed as an autoimmune disease.

Immunity refers to the ability of the body to defend itself against harmful microbes, pathogens and foreign bodies. When a harmful agent enters the bloodstream, the immune system recognises it and initiates a cascade of reactions which leads to the production of many components to neutralise the infection. This process is known as sensitisation and directs the immune system specifically against the infective agent. In an autoimmune disease there is sensitisation of the immune system to an otherwise harmless substance, which in the case of coeliac disease, is the protein found in gluten.

Coeliac disease may present in children or adults. It is sometimes triggered or becomes active after surgery, pregnancy, childbirth, viral infection or severe emotional stress.

In most people coeliac disease is asymptomatic. Some people experience the typical gastrointestinal symptoms while in others the disease is non-specific, which means the small intestine is able to absorb enough nutrients to prevent symptoms. In coeliac disease there is no typical presentation.

Symptoms

Common gastrointestinal symptoms include chronic diarrhoea, abdominal discomfort, bloating and distension. Symptoms may or may not occur in the digestive system. For example, one patient might have diarrhoea and abdominal pain, while another may complain of irritability or depression. In fact, irritability is one of the most common symptoms in children. Many symptoms (e.g. fatigue, anaemia, weight loss, bone pain, delayed growth and failure to thrive in infants) are secondary to malnutrition. Other possible symptoms include behavioural changes, muscle cramps, tingling numbness in the limbs, mouth ulcers, dermatitis, tooth discolouration and missed menstrual periods. Many coeliac patients are diagnosed through an abnormality on the blood test. This is usually in the form of iron deficiency or even anaemia.

Diagnosis

Coeliac disease can be difficult to diagnose because symptoms are similar to those of other diseases including irritable bowel syndrome, Crohn’s disease, ulcerative colitis, diverticulosis, intestinal infections, chronic fatigue syndrome and depression. Diagnosis is suspected on the basis of the symptoms and signs enhanced by laboratory and x-ray studies. Diagnosis is by the gastroenterologist through endoscopy. Endoscopy is done by introducing an endoscope, a flexible tube carrying a tiny camera and fibre optics through the mouth and stomach into the small intestine. This allows the gastroenterologist to see the lining of the small intestine and look for abnormalities. It also allows for a sample of intestinal tissue (a biopsy) to be obtained for examination by the pathologist under a microscope and checked for damage to the intestinal lining and villi. Biopsy of the small intestine is required to diagnose coeliac disease. The lining has to show atrophy or shrinking of the villi together with inflammation in the underlying mucosal tissue. The diagnosis can then be confirmed by clinical and microscopic improvement when the patient is placed on a strict gluten-free diet.

Antibodies are complexes produced by the immune system in response to substances that the body perceives to be threatening. Coeliac disease may be strongly suggested through the presence of particular antibodies in the blood. Such blood tests are used to screen for coeliac disease especially in at-risk patients for example, those with family members who have coeliac disease. A blood test does not definitively diagnose the presence of coeliac disease and positive blood tests should be followed up with an endoscopy, small bowel biopsy and histological analysis.

Treatment

The standard treatment for coeliac disease is the removal of all gluten-containing food from the diet. For many patients, this is all that is needed to control symptoms, heal existing intestinal damage and prevent further damage to allow the villi to regrow and regain function. Improvements can begin within days of starting a gluten-free diet and the small intestine is often completely healed within 3 to 6 months in those on a strict diet.

The gluten-free diet is a lifetime requirement. Eating any gluten, no matter how small an amount, can damage the intestine. This is true for anyone with the disease, including patients without noticeable symptoms.

Diet and therapy

A proportion of patients with coeliac disease do not improve on the gluten-free diet and need to receive nutritional supplements. Supplementary vitamins and minerals (especially iron), are given according to the deficiency. While mild cases of coeliac disease may not require any supplementation, severe cases require comprehensive intravenous replacement. Drug treatments are being evaluated for unresponsive coeliac disease. These patients may need to be monitored for signs of complications relating to the disease including lymphoma, osteoporosis and seizures among others.