High Quality Content by WIKIPEDIA articles! X-linked ichthyosis (XLI) (also known as "Steroid sulfatase deficiency," and "X-linked recessive ichthyosis") is a skin condition caused by the hereditary deficiency of the steroid sulfatase (STS) enzyme that affects 1 in 2000 to 1 in 6000 males. XLI Manifests with dry, scaly skin and is due to deletions or mutations in the STS gene. XLI Can also occur in the context of larger deletions causing contiguous gene syndromes. TReatment is largely aimed at alleviating the skin symptoms.IN the 1960s, recessive x-linked ichthyosis was distinguished clinically from other ichthyoses.THe major symptoms of XLI include scaling of the skin, particularly on the neck, trunk, and lower extremities. THe extensor surfaces are typically the most severely affected areas.