IGHE and Alzheimer disease: AD can be classified as extrinsic and intrinsic AD depending on whether immunoglobulin E (IgE) specific to an external allergen is involved; IgE-associated AD (extrinsic AD) is the classical type of this disease and has a high prevalence, whereas the prevalence of non IgE-mediated AD (intrinsic AD) is approximately 20% [4].