The epidermal differentiation complex (EDC) on chromosome 1q21.3 includes AD and psoriasis risk loci in close proximity.9–12 Null mutations in the gene encoding filaggrin (FLG [MIM 135940]) represent the strongest known risk factor for AD13,14 and account for at least a proportion of AD risk within the EDC, but FLG-null mutations are not associated with psoriasis.15,16 A deletion of the late cornified envelope genes LCE3B-LCE3C (MIM 612614, 612615) represents a genetic substrate for psoriasis within the EDC,17,18 but this deletion is not associated with AD.19 Here, LCE3C is linked to Alzheimer disease.