Eosinophilia Associated With Immune Deficiency

The differential diagnosis of eosinophilia is broad and includes infections, malignancies, and atopy as well as inborn errors of immunity (IEI). Certain types of IEIs are known to be associated with elevated numbers of eosinophils and frequently elevated serum IgE, whereas for others the degree and frequency of eosinophilia are less established. The molecular defects underlying IEI are heterogeneous and affect different pathways, which highlights the complex regulations of this cell population within the immune system. In this review, we list and discuss clinical manifestations and therapies of immune deficiency or immune dysregulation disorders associated with peripheral blood or tissue eosinophilia with or without raised IgE levels. We present illustrative case vignettes for the most common entities and propose a diagnostic algorithm aiming to help physicians systematically to evaluate patients with eosinophilia and suspicion of an underlying IEI.