Recessive X-linked ichthyosis

Recessive X-linked ichthyosis (XLI), also known as steroid sulfatase deficiency or X-linked ichthyosis, is a genetic skin disorder caused by mutations or deletions in the STS gene on the X chromosome, which encodes the enzyme steroid sulfatase. This enzyme deficiency leads to accumulation of cholesterol sulfate in the skin, resulting in abnormal desquamation (shedding of the outer skin layer). The condition predominantly affects males, while females are typically carriers who may show mild or no symptoms. The hallmark feature of XLI is the presence of dark, polygonal, adherent scales that most prominently affect the trunk, extremities, and neck, while typically sparing the palms, soles, and flexural areas (skin folds). Skin changes are usually apparent at birth or within the first few months of life, often presenting initially as peeling of the skin in the neonatal period. The scales tend to worsen during cold, dry weather and may improve somewhat during summer months. Corneal opacities (comma-shaped corneal stromal opacities) can occur in affected males and carrier females but generally do not affect vision. Cryptorchidism (undescended testes) is observed in approximately 20% of affected males and may require surgical intervention. Some patients may have an increased risk of testicular germ cell tumors. Prolonged or obstructed labor may occur in mothers carrying affected male fetuses due to placental steroid sulfatase deficiency, which impairs estrogen production necessary for cervical ripening. There is currently no cure for X-linked ichthyosis. Treatment is primarily symptomatic and focuses on skin hydration and removal of scales. Regular use of emollients and keratolytic agents such as creams containing urea, lactic acid, or propylene glycol can significantly improve the skin's appearance and comfort. Topical retinoids may be used in some cases. Patients benefit from avoiding harsh soaps and maintaining adequate skin moisture. Monitoring for cryptorchidism in affected boys and appropriate ophthalmologic evaluation are recommended as part of comprehensive care.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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