Food protein-induced enterocolitis syndrome presenting after necrotizing enterocolitis in a preterm neonate: a case report

When bloody stools occur in a very-low-birth-weight infant in the neonatal intensive care unit (NICU), necrotizing enterocolitis (NEC) is a prime consideration, though food protein-induced enterocolitis syndrome (FPIES) can be causative and is difficult to distinguish from NEC. Food allergy is an adverse reaction following exposure to food due to an abnormal immunologic response to food, and cow’s milk allergy (CMA) is the most likely form of food allergy in infants. The clinical features and proper management of patients with FPIES are important to differentiate FPIES from NEC. However, there are very few study reports of preterm infants presenting with food allergy-induced enterocolitis after NEC. Here, we report a case of a very-low-birth-weight infant born at 28 weeks of gestational age who developed recurrent episodes of bloody stools when he was fed cow’s milk or given breast milk fortified with milk after NEC recovery on day of life (DOL) 29, 46, and 54. A male preterm infant born at 28 weeks of gestational age presented with bloody stools on DOL 7. He was diagnosed with early-onset NEC with abdominal tenderness, sluggish bowel sounds, increased C-reactive protein (CRP) level and pneumatosis intestinalis (PI). After recovery from NEC on DOL 20, the infant developed three recurrent episodes of bloody stools after being fed cow’s milk or breast milk fortified with dairy milk. He was suspected of having recurrent episodes of NEC, but the infant was fairly healthy and did not present abdominal tenderness or abnormal bowel sounds on physical examination. Consecutive blood tests revealed normal CRP levels and increasing eosinophil levels. Abdominal radiograph revealed mild thickening of the small bowel, with no evidence of PI. The infant was finally diagnosed with FPIES in addition to NEC. After the infant received hydrolyzed formula, the bloody stool symptoms were finally resolved. Our case suggests that infants with recurrent episodes of bloody stools with increasing systemic eosinophils count should be considered for the diagnosis of FPIES with cow’s milk formula. Rapid improvement and non-progression of systemic symptoms and signs after removing exposure to milk protein may differentiate FPIES from NEC.