STS and ichthyosis vulgaris: Ichthyosis vulgaris (IV; OMIM: # 146700) is the most common type of hereditary ichthyosis related to the filaggrin gene (FLG; OMIM: # 135940), followed by the X-linked recessive ichthyosis (XLI; OMIM: 308100) which is related to the steroid sulfatase gene (STS; OMIM: # 300747) [2,3].