IGHE and Omenn syndrome: IEIs predominantly associated with increased IgE levels can be classified in the following: Hyper-IgE syndromes (HIES), and other conditions that can mimic HIES, such as Omenn syndrome (OS), Wiskott-Aldrich syndrome (WAS), and immune dysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) [16,17,18].