X-linked Ichthyosis is considered one of the five main types of ichthyosis (the others being Lamellar Ichthyosis, CIE, Ichthyosis Vulgaris and Epidermolytic Hyperkeratosis). X-linked Ichthyosis is less common (occurring in approximately 1 in 6,000 births), usually more severe, and occurs only in males. In X-linked Ichthyosis, the skin cells are produced at a normal rate, but they do not separate normally at the surface of the stratum corneum (the outermost layer of skin) and are not shed as quickly as they should be. The result is a build up of scales. The scales of X-linked Ichthyosis are dark like those of classical Lamellar Ichthyosis, but they usually are not as large and cover only a portion of a person’s body. Usually the face, scalp, palms of the hands and soles of the feet are free from scales, while the back of the neck is almost always affected. Additionally, X-linked Ichthyosis frequently improves in the summer. Babies with X-linked Ichthyosis often appear normal when they are born, but then skin abnormalities will almost always begin to show up by their first birthday. X-linked Ichthyosis is caused by a deficiency of the enzyme steroid sulfatase and can be detected prenatally using amniocentesis. Additionally, most adult men with X-linked Ichthyosis also have clouding of the eye’s cornea. Men with X-linked ichthyosis may also be at increased risk for testicular cancer. X-linked Ichthyosis is treated topically with emollients (to moisturize) and frequently with Alpha Hydroxy Acids. X-linked Ichthyosis is usually not considered severe enough to warrant the use of oral synthetic retinoids.