9 years old with 4 plus years history of doudenum ulcer

Hi, I’m looking for guidance regarding my 9-year-old son.
Previously diagnosed with Eosinophilic Esophagitis
Has had a non-healing duodenal ulcer for over 4 years
On H2 blockers long-term
On a strict food elimination diet since August 2025
3 follow-up biopsies show no EoE
Negative for Helicobacter pylori infection and Zollinger-Ellison syndrome
No NSAID or known medication cause
Recent imaging showed inflammation on T2-weighted scan (cause unclear)
Current decision:
His doctor is recommending either oral steroids or Dupixent. An elemental formula diet was also discussed, but this feels very difficult for a 9-year-old.
Questions:
What could cause a duodenal ulcer that hasn’t healed after 4+ years with these negative findings?
Can EoE be in remission on biopsy but still cause ongoing GI inflammation elsewhere?
Could this be food-triggered inflammation (e.g., gluten or other sensitivities) even without eosinophils?
For those with similar cases, how did you decide between steroids vs Dupixent vs elemental diet?
What additional tests or next steps would you recommend before starting these treatments?
Thank you for any insight or shared experiences