IGHE and Alzheimer disease: ,4 Hence, there have been discussions on classifying AD phenotypes by various factors including clinical features (onset age, severity, and disease course) and biomarkers (blood eosinophils and total/specific serum IgE).2, 3, 4, 5, 6, 7, 8, 9, 10, 11 In the present study, AD was classified into four distinct subgroups according to allergic sensitization status: cluster A (intrinsic), cluster B (egg white only), cluster C (multiple foods), and cluster D (inhalants).