A Casual Pre Descemet Corneal Dystrophy Found In An X-Linked Ichthyosis Related With Xp22.31 Containing Sts Gene

To report the association of X-linked ichthyosis (XLI) and pre-Descemet corneal dystrophy in a fifteen-year-old boy with a deletion of the steroid sulfatase gene (STS) in the XP22.31 locus

This patient was followed by Dermatology, Ophthalmology and Genetics department  in Sant Joan de Deu Hospital, a child hospital located in Barcelona, Spain.

A 15-year-old boy was diagnosed with X-linked ichthyosis following a genomic DNA sample examination from a saliva sample. He was monitored by the Dermatology and Ophthalmology departments every 6 months.

Slit lamp examination, anterior OCT, and specular microscopy were performed to assess the anterior segment and corneal tissue, along with visual acuity tests in both eyes. We present a case of an individual exhibiting clinical manifestations consistent with pre-Descemet corneal dystrophy and X-linked ichthyosis (XLI), confirmed by the detection of an Xp22.31 microdeletion encompassing the steroid sulfatase gene (STS).

Upon dermatological examination, flaking and scaling of the skin were observed on the forearms, elbows, and legs. Genomic DNA analysis unveiled a microdeletion within the Xp22.31 cytoband, encompassing the STS gene. Ocular findings showed normal lids and conjunctival examination. Slit-lamp examination of each cornea revealed granular gray-white opacities immediately anterior to the Descemet membrane. Pre-Descemet corneal dystrophy opacities are linked to cholesterol sulfate accumulation. No abnormalities were noted in the corneal endothelium, and the rest of the ocular examination for each eye was within normal parameters. Specular microscopic examination of the central corneal endothelium in each eye displayed a uniform cell mosaic.

Although skin changes are related to a deficiency of the enzyme steroid sulfatase, the etiology of corneal opacities is still unclear. STS deficiency results in heightened plasma levels of cholesterol sulfate. It is hypothesized that the corneal opacities may signify localized aggregations of cholesterol sulfate. These corneal pre-Descemet changes do not appear in all individuals with XLI. We suggest that the deletion in XP22.31 could be the trigger for showing pre-Descemet corneal changes. These corneal changes do not affect visual acuity, as reported in the literature. To the best of our knowledge, there is only one similar case published, confirmed by the identification of a deletion of STS.