Regarding IEI, elevated serum IgE levels are associated with several diseases, such as: i) hyper-IgE syndrome (loss-of-function STAT3 mutation); ii) Dedicator of CytoKinesis 8 (DOCK8) deficiency; iii) IPEX – Immunedysregulation Polyendocrinopathy Enteropathy X-linked syndrome (FOXP3); iv) Wiskott-Aldrich syndrome (WAS); v) Phosphoglucomutase 3 (PGM3) deficiency; vi) Comèl-Netherton syndrome (SPINK5); and vii) Loeys-Dietz syndrome (TGFBR1). Here, FOXP3 is linked to Wiskott-Aldrich syndrome.