Eosinophilic gastrointestinal disorders (EGIDs) are a heterogeneous group of emerging chronic inflammatory diseases that may affect different gastrointestinal (GI) tracts. Based on the anatomical site involved, EGIDs are distinguished into eosinophilic esophagitis (EoE) and non-esophageal forms, which are subdivided into eosinophilic gastritis (EoG), gastroenteritis (EoGE), and colitis (EoC). EoE is considered the prototype of EGIDs. Since the first description of a case series of patients with EoE, fundamental scientific advances have been achieved, culminating in the redaction of international diagnostic and therapeutic guidelines. In contrast to EoE, non-esophageal forms of EGIDs are still a clinical enigma with evidence limited to a few retrospective studies. In the last decade, an increase in the prevalence of EGIDs has been observed in the pediatric age. Unfortunately, the epidemiology of EGIDs in Italy is still inconsistent and clear estimates are not available.

Firstly, this study will allow us to assess and clarify several clinical and epidemiological aspects of pediatric EGIDs, in particular:

1. prevalence and incidence of pediatric EGIDs in Italy,
2. the clinical features and potential phenotypes of pediatric EGIDs with potential impact on therapy and management,
3. diagnostic work-up and adherence to the EoE international guidelines to improve the management, quality of care, and quality of life of affected patients.

This study has no ethical problems since EoE patients are treated according to international guidelines and those with non-esophageal EGIDs according to the latest scientific evidence.

Inclusion Criteria:

- All EGIDs patients aged 0-18 years and followed at the centers involved in the study will be considered eligible. Informed consent must be obtained from each enrolled patient and signed by a parent/legal guardian and patient (when older than six years).

Exclusion Criteria:

- This study will not include patients with:

1. a diagnosis of EGIDs made more than five years before the study participation;
2. a diagnosis of EoE not in line with current international guidelines;
3. a secondary cause of intestinal eosinophilic inflammation (inflammatory bowel diseases, autoimmune diseases, vasculitis, graft versus host disease, malignancies).

EoE and EGIDs Definition: Based on current international guidelines, EoE diagnosis requires the presence of more than 15 eos/HPF in endoscopically obtained esophageal biopsies.5 In contrast, the diagnosis of non-esophageal EGIDs should meet the following criteria:

• Chronic/recurrent GI symptoms unresponsive to standard therapies,
• A prevalent eosinophilic intestinal inflammation,
• Exclusion of secondary causes of intestinal eosinophilia (e.g., intestinal parasitosis, chronic inflammatory bowel disease, vasculitis, autoimmune diseases, graft versus host disease, tumors).