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

BACKGROUND 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 or not. OBJECTIVE This study aimed to clarify the differences in characteristics between the FPIES patients who fully met the diagnostic criteria and those who partly met them. METHODS This is a cross-sectional study using data at the time of registration in multicenter, prospective studies of FPIES patients in Japan. Children who had delayed emesis within 1-4 hours and/or diarrhea within 5-10 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, serving size that elicited symptoms, and antigen-specific IgE antibody titers. RESULTS 140 of the 225 FPIES patients fully met the diagnostic criteria, while 79 patients did not fully meet them but demonstrated reproducible symptoms. The frequencies of pallor, lethargy, and diarrhea were significantly higher in the fully-met patients, whereas the onset age, trigger foods, comorbidity and perinatal information, were comparable. Analysis of hen’s egg-FPIES patients revealed significantly higher levels of egg white- and egg yolk-specific IgE in partly-met patients, whereas the serving size eliciting symptoms was comparable. CONCLUSIONS Patients who partly met the diagnostic criteria may be a milder phenotype of FPIES, but it needs to be validated in further studies using biomarkers reflecting the pathophysiology.