Differences in Characteristics Between Patients Who Met or Partly Met the Diagnostic Criteria for Food Protein-Induced Enterocolitis Syndrome (FPIES)

Some patients with food protein-induced enterocolitis (FPIES)-like allergy do not completely fulfill the diagnostic criteria of the international consensus guideline for FPIES. However, it is unclear whether such FPIES-like patients represent a completely different population from FPIES. This study aimed to clarify differences in characteristics between patients with FPIES who fully met diagnostic criteria and those who partly met them. This was a cross-sectional study using data at the time of registration in multicenter, prospective studies of patients with FPIES in Japan. Children who had delayed emesis within 1 to 4 hours and/or diarrhea within 5 to 10 hours after ingestion of food were recruited between March 2020 and February 2022. We examined their compatibility with the diagnostic criteria of the international consensus guideline and their detailed clinical characteristics, including trigger foods, the serving size that elicited symptoms, and antigen-specific IgE antibody titers. Of the 225 patients with FPIES, 140 fully met the diagnostic criteria whereas 79 patients did not fully meet them but demonstrated reproducible symptoms. The frequencies of pallor, lethargy, and diarrhea were significantly higher in those who met the criteria fully, whereas the age at onset, trigger foods, comorbidity, and perinatal information were comparable. Analysis of patients with FPIES to hen’s egg revealed significantly higher levels of egg white– and egg yolk–specific IgE in patients who partly met criteria, whereas the serving size eliciting symptoms was comparable. Patients who partly met the diagnostic criteria may have a milder phenotype of FPIES, but this needs to be validated in further studies using biomarkers reflecting the pathophysiology.