Celiac Disease — Causes, Symptoms, Diagnosis & Gluten-Free Diet Guide — Symptoms, Causes & Treatment | MyMedicPlus

Celiac disease (also spelled coeliac disease) is a chronic autoimmune disorder in which ingestion of gluten — a protein found in wheat, barley, and rye — triggers an immune response that damages the mucosa of the small intestine. The immune attack destroys intestinal villi (finger-like projections that absorb nutrients), causing villous atrophy and subsequent malabsorption of iron, calcium, vitamins B12, D, and folate. Celiac disease affects approximately 1% of the global population, but up to 80% remain undiagnosed. It is strongly associated with HLA-DQ2 (90-95% of patients) and HLA-DQ8 genetic variants. The global prevalence of celiac disease has doubled over the past 50 years, attributed to changes in wheat gluten content and processing, gut microbiome alterations, and changing infant feeding practices. Although celiac disease requires lifelong strict dietary adherence, the gluten-free diet market has grown substantially — enabling most patients to maintain normal nutritional status and quality of life. Non-responsive celiac disease (persistent symptoms or abnormal serology despite strict GFD adherence) occurs in 7-30% and requires systematic evaluation for dietary transgressions and alternative diagnoses.

Celiac disease requires three factors: genetic susceptibility (HLA-DQ2 or DQ8 genes), gluten exposure, and an environmental trigger that initiates the immune response. Risk factors include first-degree relatives of a celiac patient (10-15% risk — much higher than the general population's 1%), other autoimmune conditions (Type 1 diabetes — 5-10% celiac prevalence; Hashimoto's thyroiditis — 5-8%; autoimmune liver disease), Down syndrome (5%), Turner syndrome (3-5%), and Williams syndrome. Infant feeding practices, gut microbiome composition, gastrointestinal infections, and timing of gluten introduction in infancy may modulate risk. Gut microbiome composition modulates risk — early antibiotic exposure, caesarean birth, formula feeding, and reduced childhood infection exposure alter microbial diversity in ways associated with increased celiac risk. Viral infections (rotavirus in particular) may act as environmental triggers initiating the autoimmune cascade in genetically susceptible individuals. The timing of gluten introduction in infancy does not affect celiac disease risk — the previously recommended delayed introduction has been shown not to be protective.

Classical presentation: diarrhoea (often steatorrhoea — fatty, pale, malodorous stools that float), abdominal bloating and cramps, flatulence, weight loss, and signs of nutritional deficiency (anaemia from iron/B12 deficiency, fatigue, mouth ulcers, bone pain from osteoporosis). Atypical presentation (increasingly recognised): iron deficiency anaemia not responding to oral supplementation, osteoporosis, short stature in children, unexplained infertility, recurrent miscarriages, peripheral neuropathy, ataxia, dermatitis herpetiformis (itchy blistering rash on elbows, knees, and buttocks — pathognomonic of celiac disease). Up to 30% of patients are asymptomatic or have minimal symptoms, diagnosed on screening. Dermatitis herpetiformis — intensely itchy, blistering vesicular rash on extensor surfaces (elbows, knees, buttocks, scalp) — is the cutaneous manifestation of celiac disease and is pathognomonic: skin biopsy shows IgA deposits at dermal papillae. It responds to a strict gluten-free diet and dapsone for rash control. Hepatitis in celiac disease (elevated transaminases in 15-55% at diagnosis, normalising on GFD) is another atypical presentation that prompts testing for celiac disease before more extensive liver workup in unexplained hepatitis.

Diagnosis requires gluten-containing diet at the time of testing. Serology: anti-tissue transglutaminase IgA (anti-tTG IgA) is the first-line test with sensitivity 93% and specificity 97%; total serum IgA must also be measured (IgA deficiency occurs in 2-3% of celiac patients, giving false-negative results — use IgG-based tests if IgA-deficient). Endomysial antibody (EMA) and deamidated gliadin peptide (DGP) IgG are alternative tests. Duodenal biopsy via gastroscopy is required for definitive diagnosis (Marsh classification 3a-3c shows partial to total villous atrophy). HLA typing rules out celiac disease if HLA-DQ2 and DQ8 are both absent (high negative predictive value). Genetic testing in first-degree relatives.

The only currently approved treatment is strict lifelong gluten-free diet (GFD). Gluten must be eliminated from wheat (including spelt, kamut, durum, semolina, farro), barley, and rye. Oats are controversial — uncontaminated pure oats are tolerated by most celiac patients but not all; introduce cautiously after mucosal healing. Safe grains: rice, maize (corn), millet, quinoa, amaranth, buckwheat, sorghum, teff. Even small amounts of gluten (below 20 ppm causes mucosal damage in sensitive individuals). Dietitian support is essential — gluten is hidden in sauces, soups, processed foods, medications, and even communion wafers. Nutritional deficiency correction: iron, folate, vitamin D, vitamin B12, and calcium supplementation as needed. Bone density assessment (DEXA scan) at diagnosis. Dermatitis herpetiformis: GFD plus dapsone (for rash control). Annual monitoring: anti-tTG IgA (should fall on GFD), full blood count, ferritin, B12, folate, vitamin D.

Undiagnosed or untreated celiac disease causes: iron deficiency anaemia, osteoporosis (from calcium malabsorption — increased fracture risk), infertility and recurrent miscarriage, peripheral neuropathy, cerebellar ataxia, and growth retardation in children. Long-term untreated celiac disease increases the risk of enteropathy-associated T-cell lymphoma (EATL) — a rare but aggressive small bowel lymphoma (lifetime risk 0.3-0.5% in diagnosed celiacs on a strict GFD; higher in undiagnosed). Other GI malignancies (small bowel adenocarcinoma, squamous cell carcinoma of oropharynx/oesophagus) are also increased. Refractory celiac disease (RCD) — non-response to GFD despite dietary adherence — is rare but can progress to EATL.

There is no way to prevent celiac disease, but early diagnosis through testing reduces long-term complications. Screen first-degree relatives (parents, siblings, children) of diagnosed celiac patients, and patients with associated autoimmune conditions (Type 1 diabetes, thyroid disease). Maintain strict gluten-free diet: read all food labels; use separate cooking utensils, toaster, and cutting boards (cross-contamination risk); communicate dietary needs when eating out; choose certified gluten-free products. Carry a 'Celiac disease' card for restaurants and travel. Join support groups (e.g., Coeliac UK). Celiac UK's food labelling standard requires under 20 ppm gluten for 'gluten-free' labelling. On strict GFD, antibody titres normalise within 6-12 months and gut mucosa heals within 1-2 years.

See your GP for testing if you have persistent unexplained GI symptoms (bloating, diarrhoea, abdominal pain lasting more than 4 weeks), unexplained iron deficiency anaemia, osteoporosis at a young age, unexplained subfertility or recurrent miscarriage, peripheral neuropathy, or if a first-degree relative has been diagnosed with celiac disease. Testing requires you to be eating a normal gluten-containing diet — do not start a gluten-free diet before testing, as it will cause false-negative results. Request dermatology assessment for any persistent itchy blistering rash on elbows, knees, or buttocks (dermatitis herpetiformis — pathognomonic of celiac disease). If already diagnosed with celiac disease and symptoms are not improving after 6-12 months of strict gluten-free diet, request a dietitian review and repeat anti-tTG IgA testing — persisting positive antibodies indicates continued inadvertent gluten exposure. See your gastroenterologist urgently for new unintentional weight loss, which may indicate refractory celiac disease or rare enteropathy-associated T-cell lymphoma.