The approach to Celiac Disease in children

Abstract

Celiac Disease (CD) is a permanent, irreversible but treatable multifactorial disease triggered by the ingestion of gluten (a plant storage protein contained in wheat, barley and rye) in genetically predisposed individuals and resulting in an autoimmune small intestinal inflammation with systemic implications. While the gastrointestinal manifestations secondary to an inflammatory enteropathy with variable degrees of severity are what defined it for many decades, CD is in fact characterized also by a wide range of extra-intestinal complaints and elevated titers of celiac-specific autoantibodies. 1.1. Epidemiology and pathogenesis The prevalence of CD is increasing at a remarkable pace during the past few decades [1], [2], [3]. Once thought to be a rare condition, affecting no more than 1/10,000 people, thanks to the availability and widespread use of specific and sensitive serological markers, CD is now recognized worldwide as a common disorder, with a prevalence varying between 0.3 and 3 per 100. Only a limited portion of the expected celiac patients are however actually identified, with proportions varying between different countries: in the USA, even though overall CD prevalence is estimated to be around 1%, only about 15% of this population (including children and adults) has been diagnosed and can therefore be treated [4]. This phenomenon of under-diagnosis is likely due to a combination of inadequate awareness and a high prevalence of asymptomatic or oligo-symptomatic patients. Like most multifactorial disorders, CD is the result of a complex interaction between genes, immune status of the host, and environmental triggers. Gluten is a heterogeneous molecule. The gluten fractions that are toxic to celiac patients are a mixture of alcohol-soluble proteins called gliadins. Gliadins are rich in glutamine and proline residues, which even the healthy human intestine cannot fully digest. As a result, intact gliadin peptides are left in the lumen, and some cross the intestinal barrier. These fragments come into contact with the intracellular enzyme tissue transglutaminase (tTG), which deamidates them, leading to a change in shape and increased negative charge. This creates peptides that can easily be captured by the HLA-DQ2 and/or DQ8 molecules expressed on the surface of the lamina propria-associated antigen-presenting cells (APCs) and are presented to CD4+ T cells triggering an inflammatory reaction [5]. The end result of this autoimmune-triggered inflammatory reaction is a varied degree of small intestinal mucosal damage, typically more severe proximally than distally. The role of additional environmental factors is still the object of an intense research. Recently, our group showed evidence for a plausible role of an otherwise innocuous viral infection (Reovirus) in creating a pro-inflammatory milieu conducive to the development of overt CD [6].