What is coeliac disease?
Coeliac disease (CD) or gluten sensitive enteropathy is a condition that is characterised by inflammation and erosion to the lining of the small intestine – the section of the digestive system that connects the stomach to the large intestine or colon. The small intestine helps to digest and absorb food and nutrients.
This damage is caused by the consumption of gluten. Gluten is a mix of proteins found in wheat, barley and rye, and therefore is present in many foods, such as bread, biscuits, cakes and pasta, that contain them.
Coeliac disease is not a food allergy, and it is more than just food intolerance. It is an autoimmune disease. Autoimmune diseases are those in which the body’s immune system attacks its own tissues. In coeliac disease these tissues are those of the small intestine – although other organs may be affected.
Once it has developed the disease is permanent and presently incurable, but symptoms can be resolved and damage reversed in virtually all cases when gluten is removed from the diet.
(Coeliac is pronounced see-lee-ack and is spelled celiac in North America.)
The condition has several other names, including: cœliac disease (with œ ligature), c(o)eliac sprue, non-tropical sprue, endemic sprue, gluten enteropathy or gluten-sensitive enteropathy, and gluten intolerance. The term coeliac derived from the Greek κοιλιακός (koiliakós, "abdominal"), and was introduced in the 19th century in a translation of what is generally regarded as an ancient Greek description of the disease by Aretaeus of Cappadocia.
Coeliac disease can affect many organs and systems in the body, producing any number of a wide range of non-specific symptoms that vary in severity between individuals. Some people have few or no obvious symptoms.
Symptoms in adults
The possible symptoms are:
Diarrhoea, fatty stools, bloating, wind, abdominal pain, constipation, nausea, indigestion, sickness, loss of appetite, heartburn, weight loss.
Deficiency of iron (leading to anaemia), vitamin B12, folic acid and other vitamins and minerals. This is caused by the poor absorption of nutrients due to the damaged lining of the small intestine.
Skin and hair
Dermatitis herpetiformis (an itchy and blistering skin rash), hair loss, mouth ulcers.
Muscle wasting, muscle spasms, muscle or joint pain, osteopenia or osteoporosis (thinning or brittle bones), defective dental enamel.
Delayed puberty, lowered fertility, recurrent miscarriage and early menopause.
Numbness, tingling in the hands or feet (neuropathy), seizures or epilepsy, unsteadiness (ataxia) or shaking.
Palpitations, irregular heartbeat, shortness of breath.
Tiredness, lethargy, pallor or poor growth.
Anxiety, depression and mood swings.
Presentation of symptoms in adults
In the past the typical adult with coeliac disease would present to a doctor with severe digestive symptoms and significant, developed signs of malnutrition. Doctors do still occasionally see such patients, but they are no longer the common presentation. Nowadays, people consult their doctor earlier in the course of the disease with milder, vague symptoms.
So doctors tend to see patients with symptoms such as mild tummy upsets, diarrhoea, feelings of tiredness, unresolved irritable bowel syndrome (IBS) or a general case of vague ill health.
The most common symptom is still diarrhoea, but it affects only about half of new patients, and it may be intermittent.
Other commonly reported symptoms are lethargy or tiredness (possibly due to anaemia), weight loss, abdominal discomfort or pain and bloating.
The symptoms can develop so gradually that patients may not recognise that their health is slowly deteriorating. Often, when they do realise it, they may only have a vague sense of when the decline began.
Symptoms in babies and children
Infants and children can present with some of the symptoms common to adults with coeliac disease, but typical symptoms generally include:
Diarrhoea or abnormal or pale stools, swollen abdomen, poor appetite or refusal to feed, vomiting, constipation.
Behavioural problems, tearfulness, irritability.
Tiredness, signs of malnourishment, weak or wasted muscles, stunted growth or poor weight gain.
Presentation of symptoms in children
Typical childhood coeliac disease is characterized by the onset of obvious symptoms at between six months and two years (i.e. soon after the usual introduction of grains), including pale diarrhoea, vomiting, swollen abdomen, muscle wasting, failure to gain weight, and general physical and emotional ill health.
Older children are more likely to have less severe digestive troubles, which may be intermittent. There may be delayed growth or puberty. There may be defects in tooth enamel, nutritional deficiencies and behavioural problems as well.
Teenagers are more likely than other age groups (adults included) to show no symptoms at all, but any of the typical symptoms may be present.
Screening studies suggest that around 1 per cent of Western populations have coeliac disease. However, only around 10–15 per cent of those with the disease are diagnosed – meaning that at least 85 per cent of those with coeliac disease are unaware and remain undetected. In the UK, this is estimated to represent about 500,000 people.
Onset and diagnosis
Coeliac disease can present at any point in life, from six months onwards and even well into old age. Until recently it was believed that the detection of the disease in later life implied a long-standing undiagnosed case of coeliac disease, but new research has shown that this is not necessarily true.
The disease can be triggered at any age, even after many years of gluten tolerance.
The peak age for diagnosis is among children under ten and in adults in their 40s – but increasing numbers are being diagnosed in older age.
The average time for diagnosis in UK patients is a staggering 13 years following the initial reporting of symptoms. Increased awareness among the medical profession and the general public is likely to mean that this figure reduces sharply in years to come.
Susceptibility and risk factors
In recent years, thanks to ever more cutting-edge research, we have come to learn more about who is susceptible to coeliac disease and which factors determine whether you may develop it.
However, the full picture is not yet clear.
Undoubtedly, there is a genetic component to coeliac disease. If you have an identical twin with coeliac disease, there is at least a 70 per cent chance you already will have it or develop it later. If a first-degree relative (parent, sibling, and child) has the disease, you are ten times as likely as the general population to have it (a 10 per cent chance). If a second-degree relative (grandparent, aunt, uncle, nephew, and niece) has coeliac disease, you are twice as likely as the general population to have it (a 2 per cent chance).
In recent years scientists have unlocked more genetic secrets of coeliac disease, and we now know that virtually all people who develop the disease have one of two genetic tissue types, called HLA-DQ2 and HLA-DQ8.
However, this is also true of around a third of the non-coeliac population, so clearly these genes are required, but not sufficient, for the development of coeliac disease.
Other genes that determine immunity, autoimmunity and possibly the functioning of the gastrointestinal system are also likely to be involved, but it is not known yet know what these are and how many may be required.
Gluten and diet
Obviously, gluten must be present in the diet for coeliac disease to be expressed. Generally, the more gluten consumed, the more severe any symptoms, and possibly the greater the number of types of symptoms experienced. It is also possible in some cases that the quantity – and, indeed, type – of gluten consumed could be involved in triggering the disease in some individuals.
Modern breeds of wheat could be more problematic than ancient and traditional gluten grains, and the form in which they are consumed – typically, as highly processed white flour in bread, pastas, cakes and biscuits – may contribute too.
The age of introduction of gluten into the diet may be a factor as well. ‘Leaky gut’ Studies from the USA suggest that patients with coeliac disease are more likely to have a so-called leaky gut – that is, an intestinal lining that is more permeable than normal, and that allows incompletely digested food fragments, which are normally excluded from being absorbed, instead to pass through and potentially trigger an immune response in the body.
For most people, there appears to be no clear reason or cause for the onset of symptoms of coeliac disease, but in others, it seems connected to an obvious trigger event. It is possible that these events are involved in either triggering the disease itself or in inciting more obvious signs in existing coeliac disease that has been previously symptom-free.
- A bout of severe stress
- Pregnancy or childbirth
- Food poisoning or gastroenteritis – often associated with overseas travel and perhaps with the use of antibiotics
- Gastrointestinal surgery – again perhaps with antibiotics being taken.
Disturbance of the gut bacteria population, which helps to maintain gut health, appears to be a common denominator in the obvious triggers. This disturbance could make the gut leakier and increase the likelihood of an immune response.
Other, unknown and subtler trigger events may also be involved. It may be the case that a trigger event is required in all cases – perhaps with the exception of infants who develop coeliac disease soon after gluten introduction.
More women than men are diagnosed with coeliac disease, and while it is probable that this goes for undiagnosed cases too (for other autoimmune conditions tend to affect more women than men), it is possible that women are more likely to be diagnosed because they make more visits to their doctors.
It may also be related to pregnancy, when immune function is altered.
Patients with other autoimmune conditions are more likely to have coeliac disease. Around 3 per cent of the population have an autoimmune disease, and around 30 per cent of coeliac disease patients have at least one other auto-immune disease.
Type 1 diabetes (insulin-dependent diabetes)
Around 4 per cent of those with type 1 diabetes have coeliac disease – that is four times the figure for the normal population.
Autoimmune liver disease
At least 5 per cent of those with one of the several types of autoimmune liver disease will have coeliac disease.
Autoimmune thyroid disease
Up to 7 per cent of those with thyroid disease may have coeliac disease.
Other autoimmune disease
There appear to be associations with other autoimmune conditions such as Sjögren’s syndrome, inflammatory bowel diseases (Crohn’s disease and ulcerative colitis), psoriasis, Addison’s disease and rheumatoid arthritis.
People with Turner’s syndrome, Williams’ syndrome or Down’s syndrome have an increased risk of coeliac disease – as do their first-degree relatives.
The coeliac spectrum
Although previously thought of as a ‘black or white’ disease – you either had coeliac disease or you didn’t – this is no longer considered an accurate reflection of the case. We now know that there is a ‘spectrum’ of manifestations and that it is not clear cut.
Typical coeliac disease
This is the classical version – characterized by diarrhoea, weight loss, malnutrition and, in children, failure to thrive. There is usually quite severe damage to the small intestine.
Atypical coeliac disease
In this form, digestive symptoms may be mild or lacking, and instead there may be symptoms of poor nutrient absorption, such as tiredness, anaemia, irregular heartbeat (suggesting iron deficiency), bone problems (suggesting calcium deficiency) and skin or neurological problems.
This is the type more commonly encountered nowadays and these symptoms are often seen.
Silent coeliac disease
This is coeliac disease without symptoms, but with underlying damage to the intestinal lining. Silent coeliac disease can develop into typical or atypical over time.
Potential coeliac disease
This term is used to describe those patients with a normal gut lining but positive blood (and perhaps other) tests typical of gluten sensitive enteropathy.
Latent coeliac disease
A patient, typically a child, who has been previously found (while on a normal diet) to have coeliac-related damage to the intestinal lining that at a later date recovered, and who has since resumed or remained on a normal diet without any relapse, may be said to have latent coeliac disease. Regular monitoring is advised.
Dermatitis herpetiformis (DH) is an intensely itchy skin condition, closely linked to coeliac disease, and characterized by blistery, reddened patches, usually on the elbows, knees, buttocks or scalp. It typically affects adults. Like gluten sensitive enteropathy, it is caused by gluten, and may be regarded as the skin manifestation of coeliac disease – although some consider it a separate condition.
Patients may have symptoms of coeliac disease too, but most will not. Of this latter group, many are found to have underlying damage to the gut lining or abnormal blood test results for coeliac disease when investigated.
Gluten ataxia and gluten neuropathy
These are neurological forms of gluten sensitivity, again closely linked to coeliac disease, which have come to light in recent years. Ataxia is unsteadiness or impaired co-ordination. A neuropathy causes feelings of tingling and numbness in the hands and feet. Symptoms of gluten sensitive enteropathy may be absent.
Other gluten-related conditions
Other gluten-related conditions may be discovered. A link between gluten and schizophrenia, for instance, is being explored.
The biology of coeliac disease
Gluten sensitive enteropathy mainly affects the top section of the small intestine, a key part of the digestive system. In order to understand what happens in coeliac disease, we first need to understand how digestion works.
Most food is of no use to the body in the form in which we consume it. In order for it to be of value, it must be broken down into smaller constituents that the body can absorb and reassemble – for instance, to build new cells or to nourish and fuel existing ones. The process of breaking down food is called digestion.
Digestion occurs in the digestive tract (or alimentary canal): the muscular tube that starts at your mouth, takes in the oesophagus (gullet or food pipe), stomach, small and large intestines, and ends – nine or ten metres later – at your bottom.
The agents that help to break down the food into simpler molecules are called digestive enzymes. Many of the enzymes and chemicals needed for digestion are produced in the salivary glands, the liver, the gall bladder and the pancreas – vital organs, which together with the digestive tract make up the digestive system.
Other enzymes are secreted by the cells lining the wall of the small intestine.
At around six or seven coiled metres, the small intestine consists of three connected parts – the duodenum, the jejunum and the ileum – and it is here that most digestion and absorption of food takes place.
The upper sections of the small intestine – the duodenum and the jejunum – are the regions typically affected by coeliac disease.
What goes wrong in coeliac disease?
The inside of the small intestine is not smooth. The innermost layer that lines it is called the mucosa – the gut lining – and this is characterized by a dense array of small finger-like projections called villi. These provide a large surface area available for the efficient absorption of nutrients through the mucosa.
Gluten is quite resistant to breakdown. In people without coeliac disease, digested gluten fragments are absorbed and dealt with normally, while undigested gluten fragments pass uneventfully through and out of the body. Any gluten fragments that are absorbed do not appear to pose a problem. But those with gluten sensitive enteropathy aren’t so lucky. It seems the lining of the coeliac gut is more ‘leaky’, allowing gluten fragments through more easily.
As people with coeliac disease are genetically predisposed to a greater immune sensitivity to gluten, this triggers a response. The reaction is complex, but it is essentially inflammatory and defensive – an attempt by the body to attack the gluten, which it perceives as an invader. The end-result is damage to the villi. Over time the villi can become eroded and flattened, sometimes severely, occasionally totally. This is called villous atrophy.
Untreated, this can cause two key problems.
First, the ability to produce digestive enzymes is hampered, meaning undigested foods pass through the system, to get fermented in the large intestine by bacteria, causing diarrhoea, gastric pain and bloating.
Second, damaged villi are less efficient at absorbing nutrients, meaning an increased risk of malnutrition and its complications, such as anaemia, infertility and bone disease. And, as we know, these are the typical signs of undiagnosed coeliac disease.
The changing worldwide picture
While the overall prevalence of coeliac disease is thought to be around 1 per cent in the West, there are variations among nations – for example, 2 per cent in Finland and 2.5 per cent in Mexico. Several studies show that the prevalence of coeliac disease has increased five-fold, from 0.2 per cent, in the past 35 years, and that it continues to rise, especially among the elderly.
The reasons must be environmental, as the genetic status of the population cannot have changed significantly in such a short period.
The problem of coeliac disease in the developing nations is serious.
It is a common, often undiagnosed and little-known problem in northern India, where wheat is widely consumed (the traditional southern Indian diet is gluten-free), and may be the cause of malnutrition in many children. Some North African rates can be high, though this problem is a little offset by the availability of other traditional grains, such as corn, millet and sorghum, which probably results in a lower expression of the disease. The Saharawi people of southern Algeria demonstrate a coeliac disease prevalence of a staggering 7 per cent and are among those most in need of better medical support.
A case-finding strategy is considered the best way to tackle the so-called coeliac disease ‘iceberg’, by screening all patients with any symptoms possibly indicative of coeliac disease – such as anaemia or osteopenia – or with a family history of coeliac disease, or who have been diagnosed with IBS (often misdiagnosed instead of coeliac disease).
One US study showed that the incidence could be increased up to 30 or 40 times with intensive case-finding. Nevertheless, this is not enough. Several Italian studies have shown that no matter how intensive the case-finding, you can never reach the expected 1 per cent prevalence, and usually attain only 0.5 per cent. This has been proposed by some as a strong argument for mass screening, although this has ethical ramifications.
There are few parts of the world where gluten is not consumed – some south Saharan nations, some parts of the Far East, and New Guinea. Thanks to the general Westernization of the global diet, gluten consumption is likely to continue to rise, and with it the incidence of coeliac disease. Undetected cases will cost economies and health services dearly, and this is likely to remain a huge international challenge in the coming decade.