A study from Japan reported that c.3321delA is associated with elevated IgE levels [38], but we were unable to replicate that association in this study, which is consistent with the south China [11] and Polish [37] studies.Above all, according to our results, mutation c.3321delA was associated with several AD phenotypes, and AD patients with c.3321delA tended to have earlier age of onset, though the association is not significant. Here, IGHE is linked to Alzheimer disease.