This case of MEN1 with pancreaticoduodenal gastrinomas, accompanied with a high level of serum gastrin (≥3000 pg/mL, normal: ≤200 pg/mL), developed severe esophageal stenosis and complained of dysphagia, despite administration of full-dose PPI. The gene discussed is GAST; the disease is gastrin-producing neuroendocrine tumor.