Genes Associated With Celiac Disease Studied

The objective of this research was to identify the genes associated with celiac disease. The author of the PhD thesis is Ms Itziar Zubillaga Azpiroz. Her thesis was entitled, "Molecular genetic analysis of celiac disease and its contribution to diagnosis."

It is currently known that 40% of the genetic tendency to contracting the illness is due to Class II HLA genes — specifically to HLA-DQA1 and HLA-DQB1 genes. In her work, Ms Zubillaga analysed HLA Class II genes in a number of celiac patients and she showed once again that the presence of HLA-DQA1, HLA-DQB1 and HLA-DRB1 genes confers a genetic susceptibility to contracting the disorder. The data obtained from the analysis confirmed that, in the case of patients analysed, there is a genetic imbalance in these genes.

The precise analysis of these genes enabled the researcher to produce a graphical-format gradient of the genetic risk of suffering from the disorder – as a function of the Class II HLA genes carried by the individual. The greatest genetic risk occurs when the patient is a carrier of the two susceptible genes; carriers of a single copy of the HLA-DQ2 and HLA-DQ8 molecules are at medium risk and, finally, there are those carriers of at least one of the HLA genes that code for the HLA-DQ2 molecule.

The literature published shows that 90-95% of patients with celiac disease have illness-related HLA genes. 90% of these are carriers of the HLA-DQ2 molecule. From an overall perspective, the thesis author confirmed that most of the patients studied for the research (96.56%) were genetically characterised as being carriers of the HLA genes associated to celiac disease — i.e. a greater percentage than that cited in the literature.

Contribution to diagnosis

Focus was also on determining to what extent intestinal biopsy in the initial diagnosis of the disease can be substituted by the joint use of serological markers and genetic markers. Results showed that this combination of markers provides a positive predictive value of 100% and a negative predictive value of 97%, which clearly shows that the combination put forward is a valid alternative to intestinal biopsy. All those patients in which celiac disease was suspected and who showed both serological and genetic markers fixed for the diagnosis of the disease in these analyses proved in the end to be celiac sufferers.

Genetic disease and autoimmune system

Celiac disease is caused by a permanent intolerance to proteins present in certain cereals and occurs in genetically prone individuals. This intolerance presents itself as chronic inflammation of the small intestine. The results support the view that celiac disease is a genetic pathology, given that 10% of first-order relatives of sufferers also have the disorder. The current understanding is that of an autoimmune disease that can be treated effectively by excluding gluten from the diet.