Among such Mendelian diseases, a report of a family of Darier’s disease, an autosomal dominantly inherited skin disorder, in which major affective disorders including bipolar disorder co-segregated (4), is of particular interest because the causative gene was found to be ATP2A2, which encodes SERCA2, a Ca2+ pump on the endoplasmic reticulum (ER) (5–8). The gene discussed is ATP2A2; the disease is Darier disease.