Coeliac disease: What is it?
Coeliac disease is an autoimmune disease that affects the small intestine in response to the ingestion of gluten, a protein found in several types of cereals, including wheat, barley and rye. Ingestion of gluten causes inflammation in the small intestine, resulting in damage to the intestinal villi, microprotrusions responsible for the absorption of nutrients.
Coeliac disease affects about 1% of the world’s population and, in Italy, it is estimated that there are about 600,000 people affected by this condition. Many coeliac patients are unaware that they have this condition and, by consuming gluten daily, they manifest the symptoms of the disease and risk complications. Early diagnosis and a gluten-free diet are essential in order to improve the quality of life and prevent long-term health problems.
What causes this?
Only 3% of coeliac patients have a genetic predisposition, but various environmental factors can contribute to the onset of coeliac disease. An important role in the onset of coeliac disease is played by infections of the digestive system. In addition, the presence of other autoimmune diseases, such as type 1 diabetes mellitus and autoimmune thyroiditis, increases the risk of developing coeliac disease up to 10 times compared to the general population.
What are the symptoms?
Gluten can cause several symptoms with varying severity. In the classic form, the most frequent are:
- diarrhoea;
- abdominal swelling;
- abdominal pain;
- weight loss;
- intestinal malabsorption;
- delayed growth in children.
There is an increase in the number of diagnosed cases of the atypical form of coeliac disease in adults. Symptoms of the atypical form include:
- tiredness and fatigue;
- alopecia;
- weight loss;
- recurrent aphthosis;
- hypoplasia;
- recurrent abdominal pain;
- vomiting;
- increased level of transaminases;
- menstrual cycle disorders;
- infertility and repeat miscarriages;
- osteopenia and osteoporosis.
In some patients, coeliac disease can cause dermatitis herpetiformis, also known as cutaneous coeliac disease, characterised by itchy blisters and boils mainly located in the lower back, elbows and knees.
Almost all coeliacs respond perfectly to a gluten-free diet.
Coeliac disease test: who is it for?
Currently, it is not justified to conduct screening tests for coeliac disease on sections of the population that do not show any complaints; on the contrary, it is recommended that those with the following symptoms be tested for coeliac disease:
- Coeliac disease symptoms
- First-degree family history of coeliac disease
- Autoimmune diseases
Diagnosis and tests for coeliac disease
The tests used to diagnose coeliac disease include:
- Antibody assay
- Intestinal biopsy.
Blood assay of antibodies and autoantibodies
Particularly important is the blood assay of antibodies and autoantibodies such as anti-tissue transglutaminase (tTGA, the most widely used for diagnostic purposes), anti-endomysium antibodies (EMA, directed against intestinal cell components) and anti-gliadin antibodies (AGA, directed against gluten components and less clinically important due to the high false positive rate). Patients with high anti-endomysium and anti-tissue transglutaminase antibody titres have a greater than 95 per cent probability of being coeliac.
Pre-analysis recommendations
In the period prior to performing blood tests, it is recommended not to limit gluten in the diet; otherwise, the results of the tests may be falsified. If the levels of these antibodies appear higher than normal, the patient is likely to have coeliac disease and further investigative tests, such as an intestinal biopsy and an examination to check whether the villi are damaged or atrophied, are necessary. Once coeliac disease has been diagnosed, it is necessary to perform periodic checks for autoantibodies, iron, folate and other substances in the blood, which vary according to the level of inflammation.
Osteoporosis and Coeliac disease: the importance of bone densitometry for adults
In adults at least 18 months after the diagnosis of the disease, bone densitometry is recommended to assess whether osteoporosis is present. A deficiency of nutrients and, in particular, calcium and vitamin D, caused by intestinal malabsorption can, in fact, make bones weak and fragile (osteoporosis).
HLA typing to assess the risk of coeliac disease
To assess an individual’s predisposition to develop coeliac disease, HLA typing is recommended, a susceptibility test that is based on the presence/absence of risk factors (HLA-DQ2.2, HLA-DQ2.5, HLA-DQ8 or HLA-DQB1*02). The presence of one of the HLA combinations increases the risk of coeliac disease, while the absence of them makes the development of the disease unlikely. It is a genetic test that can help resolve dubious cases and is mainly used for its negative predictive significance. Thus, in the diagnostic practice of coeliac disease, the main role of HLA typing is to rule out coeliac disease, particularly in individuals belonging to groups at risk of developing the disease.
The impact of the Gut Microbiota on the onset of coeliac disease
Several studies have shown that an alteration of the intestinal microbiota can promote or even determine the onset of celiac disease. Alteration of the intestinal microbiota (dysbiosis), which can be assessed by specific state-of-the-art tests, can determine at the intestinal level:
- Reduced gliadin digestion
- Alteration of the barrier function of the intestinal mucosa
- Alteration of the local immune and inflammatory response
These factors in genetically predisposed persons in combination with a viral infection or stressful situations can lead to the onset of coeliac disease. Not infrequently, even with a gluten-free diet, there is persistence of intestinal symptoms due to a failure of the intestinal flora to recover. Indeed, there are frequent cases of people with coeliac disease who, despite a gluten-free diet, see their intestinal symptoms worsen, and their microbiota show significant alterations.
Comparison of duodenal biopsies between patients with coeliac disease and healthy patients
Comparing the duodenal biopsies of patients with coeliac disease with those of healthy patients shows an increase in gram-negative bacteria and a reduction in Streptococcus, Bifidobacterium, Prevotella and Lactobacillus. The lack of microorganisms in the intestinal mucosa that produce short-chain fatty acids with anti-inflammatory activity favours mucus production as a defence mechanism. Diet and lifestyle are crucial for rebalancing the microbiota, and the use of probiotics can promote the colonisation of healthy gut bacteria.
Dr Maria Luisa Casella
