Aims GI dysmotility is common in preterm infants. Necrotizing enterocolitis (NEC) may develop when dysmotility, luminal contents and gut bacteria drive inflammation. Breast feeding is notably protective. Food Protein Induced Enterocolitis Syndrome (FPIES) may mimic NEC, including distension and intramural gas. In contrast to NEC, FPIES manifests thrombocytosis and neutrophilia. We have examined whether cases initially diagnosed as NEC were due to FPIES induced by cow’s milk (CM) protein.

Methods 9 preterm infants from one tertiary centre (23–36 weeks, BW 535–1700 g) were identified as possible FPIES because of temporal link between introduction of CM and onset of acute GI symptoms. A timeline was obtained of symptoms, feeding and blood parameters.

Results 3/9 showed gastro-oesophageal reflux ± constipation, improving on breast milk exclusion and worsening on reintroduction. NEC was queried but not diagnosed. All gained weight poorly, leading to CM formula introduction, which substantially worsened symptoms. All settled on exclusion and relapsed on CM challenge, remitting only with hypoallergenic formulae. Investigations showed thrombocytosis (>400) and reduced albumin after CM introduction. 6/9 were diagnosed with NEC, two twice. All showed similar dysmotility and poor weight gain on breast milk, and in all cases NEC symptoms began within 48 h of introduction of CM formula ± fortifier or thickener. In 1/6 thrombocytopaenia and neutropaenia was consistent with classic NEC, while in 5/6 platelets increased (mean 422, range 310–550) as did wcc (mean 17, range 16–25). All settled only on hydrolysate or amino acid formula.

Conclusion The NEC-like episodes in these infants concord with classic reports of FPIES in LBW infants. Most documented cases of NEC develop thrombocytopaenia – indeed thrombocytosis is unreported. All showed dysmotility, poor weight gain and thrombocytosis on breast milk: a pattern characteristic of non-IgE-mediated allergy. CM introduction because of poor weight gain was uniformly deleterious. Recognition that non-IgE-mediated CM allergy may cause dysmotility and impaired growth in preterm infants should promote consideration of maternal milk exclusion diets while breastfeeding, or introduction of hypoallergenic rather than CM formulae. Thrombocytosis in a preterm infant with dysmotility should be a red-flag sign for non-IgE-mediated food allergy and risk of FPIES on formula introduction.