X-linked ichthyosis syndrome

X-linked ichthyosis syndrome (also known as steroid sulfatase deficiency syndrome, STS deficiency, or X-linked recessive ichthyosis) is a genetic skin disorder caused by deficiency or absence of the enzyme steroid sulfatase (STS), encoded by the STS gene on the X chromosome. In most cases, the condition results from a complete deletion of the STS gene. It predominantly affects males and is one of the more common forms of ichthyosis. The condition is characterized by the accumulation of cholesterol sulfate in the skin, leading to abnormal desquamation and the formation of dark, adherent, polygonal scales, particularly on the trunk, extremities, and neck, while typically sparing the palms, soles, and flexural areas. The skin manifestations usually appear within the first few months of life, often presenting initially as peeling or dry skin in the neonatal period. The scaling tends to worsen with age and is more prominent in cold, dry weather. Beyond the skin, X-linked ichthyosis syndrome can be associated with several extracutaneous features. Corneal opacities (corneal stromal punctate opacities) are found in a significant proportion of affected males and female carriers but typically do not affect vision. Cryptorchidism (undescended testes) occurs in approximately 20% of affected males and may increase the risk of testicular cancer if uncorrected. Some patients may have an increased risk of attention deficit disorders or other neurodevelopmental issues. Maternal carriers may experience prolonged or failure to progress in labor due to placental sulfatase deficiency, which impairs estrogen production necessary for cervical ripening. There is currently no cure for X-linked ichthyosis syndrome. Treatment is primarily symptomatic and focuses on skin care, including regular use of emollients and keratolytic agents such as urea-containing creams, lactic acid preparations, or propylene glycol to reduce scaling and improve skin hydration. Topical retinoids may be used in some cases. Monitoring for cryptorchidism in affected males is important, and surgical correction (orchidopexy) should be performed if needed. Ophthalmologic evaluation may be recommended to assess for corneal opacities. Genetic counseling is advised for affected families.

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