What Is X-Linked Ichthyosis?

X-linked ichthyosis is also called ichthyosis nigricans, and X-linked recessive genetic ichthyosis (recessive X-linked ichthyosis). It can occur on the head, neck, chest, back, abdomen, waist, skin, etc. Studies have found that the cause is related to steroid sulfatase abnormalities. Deficiency of steroid sulfatase can cause punctate cartilage dysplasia and X-linked ichthyosis overlap syndrome.

X-linked ichthyosis

X-Interlocking Ichthyosis Basic Information

Chinese name: X lamps disease

English name: X-linked ichthyosis

Alias: ichthyosis nigricans, X-linked recessive hereditary ichthyosis (recessive X-linked ichthyosis), sex-linked hereditary ichthyosis vulgaris, sex-linked ichthyosis vulgaris, sex-linked ichthyosis

Parts: head, neck, chest, back, abdomen, waist, skin.

Department: Department of Integrated Traditional Chinese and Western Medicine, Dermatology.

Related symptoms: scaly, other symptoms, abnormal pigmentation, hyperkeratosis of palms and palms.

Causes of X-linked ichthyosis

In the 1860s, X-linked recessive hereditary ichthyosis was distinguished from other ichthyosis by clinical manifestations. Later studies found that this disease is related to abnormal steroid sulfatase. Steroid sulfatase hydrolyzes sulfates, including cholesterol sulfate and steroid sulfate. Fetal adrenaline sulfate is desulfurized and becomes estrogen, which is excreted from the mother's urine. The lack of steroid sulfatase in the fetal placenta can lead to a decrease in estrogen in the mother's urine, and in some women, it can also cause the initiation of labor and the process of labor. Male patients with ichthyosis vulgaris have reduced or lacking steroid sulfatase activity in many tissues, including the epidermis, cuticle, white blood cells, and cultured fibroblasts. In addition, the enzyme substrate, cholesterol sulfate, can accumulate in scales. Leukocyte steroid sulfatase levels in female carriers are between normal individuals and male patients.

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

Pathogenesis of X-linked ichthyosis

The steroid sulfatase gene is located on the X-chromosome short arm two regions two bands and three subbands (Xp22.3), which is lacking in about 80% of patients. If adjacent sulfatase deficiency occurs, punctate cartilage dysplasia and X-linked ichthyosis overlap syndrome can occur.

In the epidermis, steroid sulfatase catalyzes the hydrolysis of cholesterol sulfate. The lack of steroid sulfatase in patients with X-linked ichthyosis suggests that hydrolysis of cholesterol sulfate is important for normal desquamation. In mice, topical cholesterol sulfate can induce desquamation abnormalities, further supporting the role of cholesterol sulfate hydrolysis in the dissociation of keratinocytes.

However, some studies have found that some patients have normal steroid sulfatase activity without corneal opacities, which indicates the genetic heterogeneity of X-linked ichthyosis. Therefore, male ichthyosis patients with normal steroid sulfatase levels cannot exclude X-linked recessive hereditary ichthyosis.

X-linked ichthyosis symptoms

X interlocking ichthyosis signs

Almost all are found in men. Onset at birth or shortly after birth. Large limbs, face, neck, torso, buttocks often show large and significant scales, with the neck, face, and trunk most affected. Individual cases or severe cases can spread to the cubital fossa, underarms and popliteal fossa. The appearance of the palms and chins is normal or slightly thickened. The scales are often brown and sticky. Female carriers can see mild scales in front of the arms and tibia. Eye slit lamp examination, some patients can see obvious corneal posterior wall or elastic layer opacity. Male patients may have cryptorchidism and testicular cancer. Skin lesions do not decrease with age.

According to clinical manifestations, skin lesion characteristics, and histopathological characteristics can be diagnosed.

Clinical manifestations of X-linked ichthyosis

Symptoms at birth or shortly after birth, with the exception of the palms and soles of the feet, all skin is affected. The axillary, elbow fossa, popliteal fossa, groin, anal girth, and external genital folds are relatively mild and slightly damaged due to their relative humidity. Skin damage, although similar to ichthyosis vulgaris, is much more severe than the latter. In the cold and dry seasons, piles of actively thick, stained brown horny scaly masses are like a black armor covering the whole body. With age, external damage such as neck, face, and scalp may decrease, but the abdomen and lower limbs become more severe. Although the hot and humid season can be alleviated, only a little less scale is accumulated. Illness accompanies lifelong. Follicular keratinizing papules do not appear on the upper arms and outside the thighs. The palmoplantar pattern is no different from that of ordinary people, and there is no hyperkeratosis.

X interlocking ichthyosis inspection and identification

X-linked ichthyosis histopathology

Excessive keratinization, the granular layer is normal or slightly thickened, and sweat glands are reduced. Pericardial inflammatory cells infiltrating the dermis, mainly lymphocytes.

Clinical manifestations of X-linked ichthyosis

Almost all are found in men. Onset at birth or shortly after birth. Large limbs, face, neck, torso, buttocks often show large and significant scales, with the neck, face, and trunk most affected.

X-Interlocking Ichthyosis Skin Features

Individual cases or severe cases can spread to the cubital fossa, underarms and popliteal fossa. The appearance of the palms and chins is normal or slightly thickened. The scales are often brown and sticky. Female carriers can see mild scales in front of the arms and tibia. Eye slit lamp examination, some patients can see obvious corneal posterior wall or elastic layer opacity. Male patients may have cryptorchidism and testicular cancer. Skin lesions do not decrease with age.