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Coeliac disease
Also known as Celiac disease · Coeliac
This common condition affects around 1 in 100 people in the UK. When someone with coeliac disease consumes gluten - a protein found in wheat, barley and rye - their immune system responds abnormally, damaging the gut lining and preventing proper nutrient absorption.
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Overview
Coeliac disease is a lifelong autoimmune disorder characterised by an abnormal immune response to gluten, a protein present in wheat, barley and rye. When individuals with coeliac disease consume gluten, their immune system mistakenly attacks the small intestine lining, specifically damaging tiny finger-like projections called villi that normally absorb nutrients. Over time, this immune-mediated damage flattens the villi, reducing the surface area available for nutrient absorption and leading to malabsorption.
The condition affects approximately 1% of the UK population, though many cases remain undiagnosed because symptoms vary widely in severity. Some people experience debilitating gastrointestinal problems, whilst others have mild or atypical symptoms that may not immediately suggest a gut disorder. Coeliac disease can develop at any age, from early childhood through to late adulthood, and currently the only effective treatment involves strict lifelong avoidance of all gluten-containing foods.
Symptoms & clinical features
The presentation of coeliac disease varies considerably between individuals. Classic gastrointestinal symptoms include persistent diarrhoea, abdominal pain, bloating and excessive wind. Some people experience constipation rather than diarrhoea. Weight loss and failure to thrive in children are common consequences of malabsorption. Many individuals report fatigue and general unwellness that can significantly affect daily life.
Atypical presentations are increasingly recognised and may include iron-deficiency anaemia that does not respond to supplementation, unexplained osteoporosis or recurrent mouth ulcers. Some people develop a characteristic itchy, blistering skin rash called dermatitis herpetiformis. Neurological symptoms such as peripheral neuropathy, balance problems or headaches occur in a minority of cases. Children may present with delayed puberty, short stature or dental enamel defects. Because symptoms can be non-specific or absent altogether, diagnosis often requires a high index of clinical suspicion.
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Affected organs
The primary target of immune damage in coeliac disease is the small intestine, particularly the duodenum and jejunum where nutrient absorption normally occurs. Destruction of intestinal villi impairs the absorption of essential nutrients including iron, calcium, folate, vitamin B12 and fat-soluble vitamins. This malabsorption can have downstream effects on multiple organ systems.
Beyond the gut, untreated coeliac disease may affect bone health, leading to reduced bone density and increased fracture risk due to calcium and vitamin D malabsorption. The liver can be affected, with some individuals developing elevated liver enzymes that typically normalise on a gluten-free diet. The skin may be involved through dermatitis herpetiformis. Additionally, the nervous system can be affected in some cases, and there is evidence suggesting links between untreated coeliac disease and reduced fertility in both men and women, though mechanisms remain incompletely understood.
Risks & severity
Coeliac disease exists on a spectrum of severity. Some individuals are diagnosed only after screening due to a family history, with minimal or no symptoms at diagnosis. Others experience severe malabsorption leading to significant nutritional deficiencies, weight loss and profound fatigue. Left untreated, the condition carries long-term health risks including osteoporosis, iron-deficiency anaemia and, rarely, an increased risk of certain intestinal cancers, particularly enteropathy-associated T-cell lymphoma, though absolute risk remains low.
Age of onset varies widely. Symptoms may emerge in infancy after gluten-containing foods are introduced, during childhood, or not until adulthood. Some people remain asymptomatic for decades despite ongoing intestinal damage. First-degree relatives of affected individuals have approximately a 10% chance of developing coeliac disease themselves, substantially higher than the general population risk. Individuals with certain autoimmune conditions, particularly type 1 diabetes or autoimmune thyroid disease, face increased likelihood of also having coeliac disease.
Genetic causes
Coeliac disease has a complex genetic architecture involving multiple genes, though the strongest genetic association involves specific variants in the human leukocyte antigen (HLA) region, particularly HLA-DQ2 and HLA-DQ8. These HLA molecules present gluten-derived peptides to immune cells in a way that triggers an abnormal immune response. However, whilst these HLA variants are necessary for coeliac disease to develop, they are not sufficient - approximately 30-40% of the general UK population carries these variants, yet only around 1% develop the condition, indicating that additional genetic and environmental factors are required.
Amongst the non-HLA genes implicated in coeliac disease susceptibility, IL21 encodes interleukin 21, a signalling protein that plays an important role in regulating immune responses. Research suggests that variants in IL21 may influence the intensity of the immune reaction to gluten and affect how T cells and B cells coordinate the inflammatory response in the intestine. The protein typically helps modulate immune cell development and function, and alterations in IL21 signalling may contribute to the breakdown of oral tolerance to dietary gluten.
The polygenic nature of coeliac disease means that susceptibility arises from the combined effect of multiple genetic variants, each contributing a small amount to overall risk. This complex inheritance pattern explains why the condition tends to cluster in families but does not follow simple Mendelian inheritance rules.
Inheritance pattern
Coeliac disease follows a polygenic or complex inheritance pattern, meaning that multiple genes - each exerting a modest effect - collectively influence an individual's susceptibility. Unlike single-gene conditions that show predictable inheritance patterns, coeliac disease risk is determined by the combination of numerous genetic variants alongside environmental factors, particularly gluten exposure.
Because of this complex inheritance, relatives of someone with coeliac disease face increased risk compared to the general population, but predicting who will develop the condition remains difficult. First-degree relatives (parents, siblings, children) have roughly a 1 in 10 chance of developing coeliac disease during their lifetime. Screening of close family members is often recommended, particularly if they have suggestive symptoms or associated conditions such as type 1 diabetes.
Diagnosis & testing
Diagnosis of coeliac disease in the UK typically begins with serological blood tests measuring antibodies against tissue transglutaminase (anti-tTG) and, in some cases, endomysial antibodies (EMA). These tests are highly sensitive and specific when individuals are consuming a gluten-containing diet. It is essential that people continue eating gluten-containing foods in the weeks leading up to testing, as avoiding gluten can lead to false-negative results.
If blood tests suggest coeliac disease, referral to a gastroenterologist for upper gastrointestinal endoscopy with duodenal biopsies is usually recommended to confirm the diagnosis. Biopsy samples are examined microscopically for characteristic villous atrophy and increased intraepithelial lymphocytes. In children with very high anti-tTG antibody levels and positive EMA antibodies, European guidelines permit diagnosis without biopsy in selected cases, though UK practice often still includes endoscopy. Genetic testing for HLA-DQ2 and HLA-DQ8 can be useful in excluding coeliac disease when results are negative, as the condition is highly unlikely without these variants, but positive HLA testing alone cannot confirm diagnosis given how common these variants are in the general population.
Management & lifestyle
The cornerstone of coeliac disease management is strict, lifelong adherence to a gluten-free diet. This means eliminating all foods containing wheat, barley and rye, including obvious sources like bread, pasta and cereals, as well as hidden sources where gluten may be used as a thickener or additive. Oats are generally tolerated by most people with coeliac disease, though they must be certified gluten-free to avoid cross-contamination during processing. Dietetic support from a specialist familiar with coeliac disease is invaluable in ensuring nutritional adequacy whilst maintaining strict gluten avoidance.
Once a gluten-free diet is established, intestinal healing typically occurs over months, with symptoms often improving within weeks. Regular follow-up is recommended, usually through annual review, to monitor adherence, assess symptom resolution and check for nutritional deficiencies. Blood tests may be repeated to confirm antibody levels are falling. Bone density scanning may be considered in adults, particularly if diagnosis was delayed. People with coeliac disease should be offered pneumococcal vaccination due to potential hyposplenism, a condition where the spleen functions less effectively.
Patients in England can access gluten-free foods on NHS prescription, though availability varies by local commissioning arrangements. Coeliac UK, the national charity, provides extensive resources, recipe guidance and a regularly updated food and drink directory to help individuals identify safe products. Referral to a gastroenterologist with expertise in coeliac disease and access to a specialist dietitian represents the standard NHS care pathway for newly diagnosed individuals.
UK care pathway
In the UK, coeliac disease diagnosis and management typically occur through primary and secondary care pathways. GPs can initiate serological screening for individuals with suggestive symptoms or relevant risk factors, including first-degree relatives of affected individuals or those with associated autoimmune conditions. Positive serology usually prompts referral to gastroenterology for confirmatory duodenal biopsy.
Once diagnosed, patients should have access to specialist dietetic input to support the transition to a gluten-free diet. Annual review, often conducted in primary care, monitors symptom control, dietary adherence and nutritional status. For complex cases - such as non-responsive coeliac disease where symptoms persist despite apparent gluten avoidance, or concern about complications - ongoing specialist gastroenterology follow-up is appropriate. Coeliac disease does not typically require clinical genetics referral given its polygenic inheritance, though genetic counselling may be relevant for families with multiple affected members seeking information about recurrence risk.
Frequently asked questions
Will I always need to avoid gluten, or can coeliac disease go away?
Coeliac disease is a lifelong condition and does not go away. Even when symptoms resolve and the intestine heals on a gluten-free diet, reintroducing gluten will cause the immune response and intestinal damage to return. Lifelong gluten avoidance is essential to maintain health and prevent complications.
Can I eat oats if I have coeliac disease?
Most people with coeliac disease can safely eat oats, but they must be certified gluten-free oats. Standard oats are often cross-contaminated with wheat, barley or rye during growing, harvesting or processing. A small number of individuals react to oats themselves, so they are sometimes introduced cautiously under dietetic supervision.
Should my children or siblings be tested for coeliac disease?
First-degree relatives of someone with coeliac disease have around a 10% lifetime risk of developing the condition themselves. Testing is particularly recommended if they have relevant symptoms, but some specialists suggest screening even without symptoms, especially in children. Speak with your GP about whether testing would be appropriate for your family members.
What happens if I accidentally eat gluten?
Accidental gluten exposure typically causes a return of symptoms within hours to days, varying by individual sensitivity. The intestine may sustain temporary damage even from small amounts. Most people recover within days to weeks of resuming strict gluten avoidance. If accidental exposure happens frequently, it may prevent full intestinal healing and increase long-term complication risk.
References
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