A case of severe eosinophilia in a preterm infant

TH2-driven manifestations of inborn errors of immunity

Monogenic lesions in pathways critical for effector functions responsible for immune surveillance, protection against autoinflammation, and appropriate responses to allergens and microorganisms underlie the pathophysiology of inborn errors of immunity (IEI). Variants in cytokine production, cytokine signaling, epithelial barrier function, antigen presentation, receptor signaling, and cellular processes and metabolism can drive autoimmunity, immunodeficiency, and/or allergic inflammation. Identification of these variants has improved our understanding of the role that many of these proteins play in skewing toward TH2-related allergic inflammation. Early-onset or atypical atopic disease, often in conjunction with immunodeficiency and/or autoimmunity, should raise suspicion for an IEI. This becomes a diagnostic dilemma if the initial clinical presentation is solely allergic inflammation, especially when the prevalence of allergic diseases is becoming more common. Genetic sequencing is necessary for IEI diagnosis and is helpful for early recognition and implementation of targeted treatment, if available. Although genetic evaluation is not feasible for all patients with atopy, identifying atopic patients with molecular immune abnormalities may be helpful for diagnostic, therapeutic, and prognostic purposes. In this review, we focus on IEI associated with TH2-driven allergic manifestations and classify them on the basis of the affected molecular pathways and predominant clinical manifestations.

Cow's Milk Allergy with Severe Eosinophilia

Because the role of eosinophils in neonates is not well understood, the clinical significance of eosinophilia in neonates is unclear. We encountered a rare case of cow's milk allergy in a premature male infant with severe eosinophilia in the neonatal period. The peripheral blood eosinophil count in this infant was 7,404/μL at birth, and he produced stools with fresh blood immediately after birth and prior to the first feedings with regular cow's milk. Although the patient's eosinophil count normalized without specific treatment within 6 weeks after birth, it is possible that the causes of the eosinophilia in this infant prior to the first feedings with regular cow's milk were different from those after the first feedings. Cow's milk allergy was diagnosed on the basis of the patient's positivity for this allergy in the challenge test and subsequent allergen-specific lymphocyte stimulation test performed at 6 months of age.