Abstract
BACKGROUND: Peripheral blood eosinophilia is identified in numerous medical conditions associated with allergic, infectious, and inflammatory processes mostly as reactive eosinophilia with or without tissue eosinophilia. In hospitalized neonates, eosinophilia is common with an inverse relationship with gestational age and occurs solely as mild eosinophilia in the majority of cases. In the literature, eosinophilia has been proposed as a possible risk factor for venous thromboembolism. However, few reports are found on thromboembolic events including portal vein thrombosis (PVT) associated with eosinophilia in the newborn period. Neonates, particularly preterm infants, are vulnerable to thrombosis due to the immature and developing hemostatic system with little reserve capacity, which occurs as catheter-related thrombosis in most cases. CASE PRESENTATION: A male newborn at 34(+ 5) weeks' gestation presented with a left portal venous thrombus and hematochezia after initial cow's milk feeding in the setting of blood hypereosinophilia for a prolonged period of time without central venous catheterization. The infant was diagnosed with PVT and food protein-induced allergic proctocolitis (FPIAP) and showed complete resolution of the conditions with expectant management with food avoidance, including the normalized eosinophil count. CONCLUSIONS: Our experience suggests that in the setting of hypereosinophilia with a prolonged duration in premature neonates, FPIAP should be suspected in case of hematochezia in otherwise healthy infants, and considering the increased thrombotic risk by the hypereosinophilia and premature newborn status, evaluation for neonatal thrombosis may be needed, including PVT with the potential risk for the more serious, but uncommon, late complications encompassing portal hypertension.