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Celiac disease

General aspects
Celiac disease is a chronic autoimmune disorder of the small intestine caused by a lifelong gluten intolerance; gluten is a substance resulting in gliadin and glutenin proteins union in the presence of water, that are contained in cereals and cereal products such as wheat, barley, spelt, bulgur, couscous, rye, seitan, kamut, triticale.celiachia comp
Presenting symptoms are chronic diarrhea, abdominal pain, swelling feeling, child growth delay, tiredness; serious complications coild be osteoporosis, diabetes mellitus, lymphomas, autoimmune thyroiditis.
The Italian frequency is about 1 in 100 individuals.
Celiac disease is one of the food-related disorders, because of the intestinal mucosa villi are flattened and prevent the efficient nutrients, vitamins and minerals assimilation. The diagnosis of celiac disease involves blood anti-transglutaminase, anti-gliadin and anti-endomysium antibodies researching and intestinal biopsy to judge a disease stage. Currently the only treatment is a gluten-free diet, if strictly followed, to disease’s slip back.
Genetics aspects

Celiac disease is a polygenic multifactorial disease: several genetic factors fix up an individual, which swallows gluten diet (environmental factor), to the disease development. In HLA histocompatibility complex there are two genes DQA1 and DQB1, each one in duplicate, which encode, respectively, the alpha and beta chain of a heterodimer (protein consisting of two different subunits) present on the surface of certain cells of the immune system.
If an individual has DQA1 * 05 and DQB1 * 02 alleles produces the DQ2 heterodimer, with an increased risk of celiac disease (about 80% of disease celiac patients is DQ2). DQA1 * 03 and DQB1 * 03: 02 alleles encode DQ8 heterodimer, with a lower risk of celiac disease (10% of disease celiac patients).
Among the disease celiac patients there are also individuals DQA1 * 05 negative, so they have different DQA1 alleles not predisposing to celiac disease, but DQB1 * 02 positive and they have, therefore, only the beta chain of DQ2 (5% of disease celiac patients). Individuals with the DQ2 heterodimer complete and homozygous for DQB1 * 02 allele (25-30% of disease celiac patients) have a higher risk of celiac disease, they are diet-resistent and they could develop lymphomas.
Depending on the observed genotype it was defined a gradient of risk of disease celiac development:
homozygous DQB1 *02> DQ2> DQ8> DQ2 only beta chain.
DQA1 and DQB1 genes are strongly associated with the DRB1 gene and in particular the DQ2 genotype is associated in 65% of cases with DRB1 * 03 (DR3) allele, in 30% with DRB1 * 11/07 or DRB1 * 12/07 ( DR5 / 7) allele; almost all DQ8 are DR4 (DRB1 * 04) and DQ2 only beta chain are almost always DRB1 *07 (DR7). DRB1 alleles not condition disease celiac risk but they can be useful to validate the test results.

Genetic test

In Tecnobios Prenatale Eurogenlab is available a genetic test for HLA DQA1, DQB1 and DRB1alleles researching. The presence of one of the HLA combinations about predisposition results in an increased disease celiac risk, while their absence makes it highly unlikely the disease development. It is a genetic test that has no absolute diagnostic meaning but it can help to resolve doubtful cases; it is mainly used for it’s negative predictive meaning, because of DQ2, DQ8 and DQB1 * 02 negative individuals get sick infrequently.

Response times

The analysis result is available within 15 working days from draw sample.

Material analyzed

The DNA is extracted from peripheral blood lymphocytes collected in EDTA tubes or from buccal swab.

Sources sites
www.celiachia.it
www.sigu.net
www.celiachiamo.com