Further, other sphingolipid metabolic enzymes that are associated with the synthesis of glucosylceramide (GCer) and sphingomyelin (SM), such as serine-palmitoyl transferase (SPT), stearoyl CoA desaturase (SCD) [20], ceramide synthases (CERS) 1–5 [20], GCer synthase (GCERS), alkyl chain elongation enzymes [20] and SM synthase (SMS), have never been implicated in the abnormal ceramide deficiency of non-lesional AD skin. This evidence concerns the gene SCD and Alzheimer disease.