IGHE and Alzheimer disease: While the complete etiology of AD is unknown, a dysregulated type 2 immune response with elevated IgE and barrier dysfunction is thought to underlie its pathogenesis.57, 58 Mast cells are elevated in the skin of patients with AD and they are thought to play a role in AD pathogenesis.59 Additionally, microbial dysbiosis is now appreciated as a potential driver of AD pathophysiology.