keratosis follicularis spinulosa decalvans keratosis follicularis spinulosa decalvans keratosis follicularis spinulosa decalvans is a rare x-linked disorder described by siemens in 1926, a disease that begins in infancy with keratosis pilaris localized on the face, then evolves to more diffuse involvement.: 580, 762 : 649, 714 keratosis follicularis spinulosa decalvansother namessiemens-1 syndrome an association with sat1 has been suggested.