Acute typical food protein-induced enterocolitis syndrome triggered by egg white: Two case reports.

Food protein-induced enterocolitis syndrome (FPIES) is a non-immunoglobulin E (IgE)-mediated food allergy characterized by gastrointestinal symptoms such as vomiting and diarrhea. Since 2018, hen's egg yolk has been the most common trigger for FPIES in Japan, whereas typical egg white (TEW) FPIES remains rare. Herein, we present two cases of acute TEW FPIES in young children. A 17-month-old girl experienced recurrent vomiting and lethargy following egg white ingestion, despite previously tolerating half an egg yolk and 5 g of egg white. Initial tests showed no sensitization markers (egg white-specific IgE < 0.1 kUA/L; ovomucoid [OVM]-specific IgE < 0.1 kUA/L; skin prick test [SPT] negative). Three oral food challenges (OFCs) at 6-month intervals at our hospital all triggered vomiting and lethargy. Procalcitonin and thymus- and activation-regulated chemokine levels remained elevated for 24 hours, and even after 31 months, the patient had not achieved egg white tolerance. A 14-month-old girl presented with vomiting and lethargy after egg white ingestion while on a strict egg yolk- and egg white-free diet. Blood tests again showed no sensitization markers (egg white-specific IgE < 0.1 kUA/L; OVM-specific IgE < 0.1 kUA/L; SPT negative). Two OFCs at 6-month intervals confirmed FPIES, and even after 2 years, the patient had not achieved egg white tolerance. These cases highlight that egg white can trigger FPIES. Thorough medical history taking and diagnostic evaluation, including OFCs, are essential to distinguish FPIES from immediate-type food allergies.