Response to Different Wheat Genotypes in Not-celiac Wheat Sensitivity

Inclusion Criteria: All the patients will meet the recently proposed criteria: * negative serum anti-tissue transglutaminase and antiendomysium (EmA) immunoglobulin (Ig)A and IgG antibodies * absence of intestinal villous atrophy * IgE-mediated immunoallergic tests negative to wheat (skin prick tests and/or serum specific IgE detection) * follow-up duration \>12 months after the initial diagnosis * at least two outpatient visits during the follow-up period. Adjunctive criteria adopted in our patients will be: * resolution of the gastrointestinal symptoms on a standard elimination diet, without wheat, cow's milk, egg, tomato, chocolate, or other food(s) causing self-reported symptoms * symptom reappearance on DBPC wheat challenge, performed as described previously. As in previous studies, DBPC cow's milk protein challenge and other "open" food challenges will be also performed. Exclusion Criteria: Exclusion criteria will be: * age \<18 years * positive EmA in the culture medium of the duodenal biopsies, even if the villi to crypts ratio in the duodenal mucosa was normal * self-exclusion of wheat from the diet and refusal to reintroduce it before entering the study * other organic gastrointestinal diseases (i.e. careful exclusion of Crohn's disease) * concomitant treatment with steroids and/or antihistamines.