Furthermore, mutations in PSENEN have also been reported in patients with HS and/or Dowling–Degos disease (37–39), which indicates that haploinsufficiency of presenilin enhancer-2 due to PSENEN mutations and reduced Notch signaling due to POFUT1 and POGLUT1 mutations both result in similar clinical consequences. This evidence concerns the gene PSENEN and histiocytic sarcoma.