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  4. X interlocking ichthyosis etiology, X interlocking ichthyosis has what reason

X interlocking ichthyosis etiology, X interlocking ichthyosis has what reason

X interlocking ichthyosis etiology, X interlocking ichthyosis has what reason

Etiology of X-interlocking ichthyosis

First, the cause of the disease

In 1960s, X-linked recessive ichthyosis was distinguished from other ichthyosis in clinical manifestations, and later studies found that this disease was related to abnormal steroid sulfate esterase. Steroid sulfurase hydrolyzes sulfates, including cholesterol sulfate and steroid sulfate. Fetal epinephrine sulfate desulfurizes groups and turns into estrogen, which is excreted from mother's urine. The lack of steroid sulfate esterase in fetal placenta can lead to the decrease of estrogen in mother's urine, and in some parturients, it can also lead to the disorder of labor initiation and labor process. In male patients with sex-linked ichthyosis vulgaris, the activity of steroid sulfate esterase is decreased or deficient in many tissues, including epidermis, stratum corneum, white blood cells and cultured fibroblasts. In addition, the enzyme substrate-cholesterol sulfate can accumulate in scales. The leukocyte steroid sulfurase level of female carriers is between normal individuals and male patients.

In men, the incidence of sex-linked ichthyosis vulgaris is about 1: 2000 ~ 1: 6000. About half of adult male patients may have comma-like corneal opacity, but it does not affect vision, and it can also appear in female carriers. The incidence of cryptorchidism and testicular cancer increased in male patients. Cholesterol sulfate levels in serum, epidermis and scales increased, and gel electrophoresis showed an increase in β-lipoprotein (low density lipoprotein), which can be used as one of the diagnostic features. When the serum cholesterol sulfate level increases from 80 ~ 200 μ g/dl to 2000 ~ 9000 μ g/dl, the diagnosis can often be confirmed.

Second, the pathogenesis

Steroid sulfurase gene is located in the short arm of X chromosome (Xp22.3), and this enzyme gene is deficient in about 80% of patients. Punctate chondroplasia and X-linked ichthyosis overlap syndrome can occur if the adjacent sulfate esterase is deficient.

In the epidermis, steroid sulfate esterase catalyzes the hydrolysis of cholesterol sulfate. The lack of steroid sulfate esterase in patients with X-linked ichthyosis indicates that hydrolysis of cholesterol sulfate is very important for normal desquamation. In mice, external application of cholesterol sulfate can induce abnormal desquamation, which further supports the role of cholesterol sulfate hydrolysis in keratinocyte dissociation.

However, some studies have found that steroid sulfate esterase activity is normal in some patients without corneal opacity, which shows the genetic heterogeneity of X-linked ichthyosis. Therefore, male ichthyosis patients with normal steroid sulfurase level cannot be excluded from X-linked recessive ichthyosis.


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