Celiac disease is an autoimmune condition where eating gluten triggers an immune response that damages the lining of the small intestine. It affects roughly 1 to 1.5% of the population, though at least half of people with celiac disease don’t know they have it. The condition is lifelong, and the only effective treatment is a strict gluten-free diet.
What Happens Inside Your Body
Gluten is a protein found in wheat, barley, and rye. In people with celiac disease, fragments of gluten slip through the intestinal lining and set off an immune reaction. Normally, the cells lining your small intestine are sealed together by tight junctions that control what passes through. Gluten disrupts those junctions, making the gut more permeable than it should be.
Once gluten fragments cross the intestinal barrier, immune cells in the gut wall treat them as threats. This triggers inflammation that gradually destroys the villi, the tiny finger-like projections that line the small intestine and absorb nutrients from food. As villi flatten and shrink, your body loses its ability to absorb iron, calcium, vitamins, and other essential nutrients. That malabsorption is what drives most of celiac disease’s wide-ranging symptoms.
Symptoms in Adults
Celiac disease is often thought of as a digestive problem, and many people do experience bloating, diarrhea, constipation, or abdominal pain. But a large number of adults have symptoms that seem unrelated to the gut, which is one reason the condition goes undiagnosed so often.
The most common symptoms in adults include:
- Iron-deficiency anemia that doesn’t respond to supplements
- Fatigue and brain fog
- An itchy, blistering skin rash called dermatitis herpetiformis
- Bone or joint pain
- Tingling or numbness in the hands and feet (peripheral neuropathy)
- Unexplained weight loss
- Cognitive impairment
Some people have no obvious symptoms at all, a form sometimes called “silent” celiac disease. The intestinal damage is still happening, though, which means complications can develop over years without warning signs.
Symptoms in Children
Children with celiac disease often look different from adults with the condition. The hallmark signs in young children are failure to thrive, a distended belly, and pale, foul-smelling stools. Because their bodies are still growing, the inability to absorb nutrients can cause short stature, delayed puberty, and damage to tooth enamel.
Neurological symptoms show up more often than many parents expect. Children with undiagnosed celiac disease may develop ADHD-like behavior, learning disabilities, headaches, seizures, or problems with muscle coordination. Irritability that seems out of proportion can also be an early clue, especially in toddlers.
The Genetic Connection
Celiac disease requires a genetic predisposition. About 90% of people with celiac disease carry a specific gene variant called HLA-DQ2, and most of the remaining carry HLA-DQ8. Together, these two markers are present in roughly 98% of celiac patients. However, carrying these genes doesn’t mean you’ll develop the disease. More than half the general population carries one of these variants, and most of them never get celiac disease. Something else, likely an environmental trigger such as an infection or stress, activates the condition in genetically susceptible people.
This is why genetic testing is useful mainly for ruling celiac disease out. If you don’t carry HLA-DQ2 or HLA-DQ8, it’s extremely unlikely you have celiac disease. But if you do carry them, further testing is needed.
How Celiac Disease Is Diagnosed
Diagnosis typically starts with a blood test that measures antibodies your immune system produces in response to gluten. The most widely used test looks for antibodies against tissue transglutaminase (called tTG-IgA). If this test comes back positive, a doctor will usually confirm the diagnosis with an upper endoscopy, where a small tissue sample is taken from the small intestine and examined for villous damage.
In some cases, the endoscopy can be skipped. When the tTG-IgA result is very strongly positive (greater than 10 times the upper limit of normal) and a second blood test for a different antibody also comes back positive, that combination is considered reliable enough for diagnosis on its own.
One important detail: you need to be eating gluten for these tests to work. If you’ve already switched to a gluten-free diet before being tested, your antibody levels may have dropped and your intestinal lining may have started healing, which can produce a false negative.
Linked Autoimmune Conditions
Celiac disease tends to cluster with other autoimmune conditions. The later you’re diagnosed, the higher your risk. People diagnosed after age 20 have about a 34% chance of developing a second autoimmune disorder, compared to roughly 10% for those diagnosed between ages 2 and 4.
Type 1 diabetes has one of the strongest associations, with about 6% overlap between the two patient populations. Hashimoto’s thyroiditis (an underactive thyroid caused by immune attack) affects roughly 3.5% of celiac patients. Other linked conditions include autoimmune liver disease, Sjögren’s syndrome, and Addison’s disease. There’s also a notable overlap with irritable bowel syndrome: as many as 10% of people diagnosed with IBS may actually have celiac disease.
What Happens If It Goes Untreated
When celiac disease goes undiagnosed or untreated for years, the ongoing intestinal damage and nutrient malabsorption lead to progressively serious problems. Bone loss is one of the most common complications, because the body can’t absorb calcium and vitamin D properly. In children, this can cause rickets or soft bones. In adults, it leads to osteoporosis.
Chronic malabsorption also contributes to infertility, nerve damage, and lactose intolerance. Some of these complications, particularly severe bone loss and infertility, may not be fully reversible even after starting a gluten-free diet. In rare cases, long-standing untreated celiac disease is associated with a type of intestinal lymphoma.
A small percentage of people develop refractory celiac disease, where symptoms and intestinal damage persist despite strict gluten avoidance for at least 6 to 12 months. One form of refractory disease responds to additional treatment and has a reasonable outlook. The other involves abnormal immune cells in the intestinal lining and carries a significantly worse prognosis, with 5-year survival rates between 40 and 58%.
Living Gluten-Free
A strict gluten-free diet is the only treatment for celiac disease. That means eliminating all wheat, barley, and rye, along with any foods, sauces, or products that contain them. For most people, the intestinal lining begins to heal within weeks to months of going gluten-free, though full recovery can take a year or longer in adults.
In the United States, any food labeled “gluten-free” must contain less than 20 parts per million of gluten, a threshold consistent with international standards. That trace amount is considered safe for people with celiac disease. Still, hidden gluten in processed foods, medications, and even cross-contamination during cooking can be a persistent challenge. Many people find it helpful to work with a dietitian during the transition to identify safe foods and spot less obvious sources of gluten, such as soy sauce, malt flavoring, and some salad dressings.
The good news is that for most people, symptoms improve noticeably within the first few weeks of eliminating gluten, and blood antibody levels typically normalize within 6 to 12 months. Periodic follow-up blood tests can confirm that the diet is working and the immune response has quieted down.