Follow-up visits are always organized in the same way. A consultation with a gastropediatrician will take place, with assessment of symptoms (PEESS score) and quality of life (PedsQL module for eosinophilic esophagitis and PedsQL 4.0 Generic Core Scales). Then, if treatment needs to be introduced or changed, a digestive endoscopy with biopsies will be carried out at 3 months to determine whether the patient is in remission or not. Depending on the results, the patient may be advised to adapt or maintain the current treatment.

Digestive endoscopies are performed in the operative room under general anaesthetic 3 months after the introduction or change of treatment. Biopsies of the upper, middle and lower thirds of the esophagus will be taken and analyzed for pathology.

Complete remission will be defined according to the following criteria:

1. Abolition of clinical symptoms as assessed by the Pediatric Eosinophilic Esophagitis Symptom Score
2. Endoscopic score: EoE Endoscopic Reference Score (EREFS) ≤ 2 in the lower, middle and upper thirds of the esophagus.
3. Eosinophilic infiltrate < 5/HPF in standard HES (Haemato-Eosin-Safran) stain on biopsies from lower, middle and upper thirds of esophagus
4. No therapeutic change at follow-up visit to assess remission

The description of the population will be carried out at baseline and during a 24 months follow-up at each consultation (M3, M6, M12, M18 and M24) by the patient's referring physician, listing :

• demographic (age, gender, lifestyle) and medical (history, allergies, etc.) data at baseline only
• Clinical data (types of symptoms, possible complications, etc.)
• Paraclinical data (endoscopic and anapathic scores at diagnosis)