What Is Ichthyosis Vulgaris?

Ichthyosis vulgaris This type is the most common, usually heavy in winter and light in summer. Infants and young children can get sick. It involves the extension of the lower limbs, especially the calf, and the flexion and folds of the limbs are not involved. Those with mild disease only show dry skin in winter, with fine-grained bran-like scales on the surface, also known as xeroderma; typical skin lesions are light brown to dark brown rhombus or polygonal scales with fixed scales in the center, free edges, and hips Hair follicle keratosis papules may also be present on the extremities of the extremities. The palmar plantars often have linear cleft palate and deepened palm prints; usually they have no conscious symptoms.

Ichthyosis vulgaris

Ichthyosis vulgaris This type is the most common, usually heavy in winter and light in summer. Infants and young children can get sick. More involved lower limb extension, especially

IV is hereditary

From the clinical manifestations, there are three main characteristics of ichthyosis vulgaris.

First, the skin damage is like "fish scale" or "snake skin", it is polygonal or diamond-shaped, attached in the middle, and the edge is upturned. The front of the calf is the most common. , The groin is often nothing unusual in these relatively humid places. Shedding dander is usually white. The patient's skin is dry and itchy in severe cases.

Second, keratized papules of the hair follicles usually appear on the outstretched side of the upper arms and thighs, and sometimes on the cheeks. When it is light, it looks like the pores are thicker, and each pore is a small point. If it is serious, these points will become obvious. If they appear in one piece, they will look like a file.

Thirdly, there are many, deep and messy hand and foot prints, and the skin of the palms and soles is rough, and even thick keratinous plaques are formed. In a dry environment, keratinous plaques are easy to crack and cause pain. It usually develops from a few months after birth to before the age of 5 years, and is most severe during puberty, and then gradually relieves. Warm and humid summers will ease, while cold and dry winters will intensify.

Figure 1 Polygonal, diamond-shaped scales of ichthyosis vulgaris, attached in the center, with raised edges, like fish scales. The lifted scales can often be torn off, forming white scaling.

Autosomal dominant inheritance. Its main genetic characteristics are: at least one of the patient's parents is sick, and each generation has the disease, the incidence rate is 50%, and the incidence is equal between male and female in each generation.

Sex-linked inheritance, also called X-interlocking inheritance. Its main genetic characteristics are: almost all of them are found in men, and women are only those who carry genes, but rarely. The male patient never inherits the gene to his son, but inherits the gene to all his daughters, and they do not develop the disease but only the carrier of the gene. Half of the carrier s sons receive the gene and develop symptoms, and Hereditary ichthyosis is blocked and the offspring are no longer inherited.

Genetically, this type belongs to the "autosomal dominant inheritance", which is manifested in that every generation in the family is sick, and there is no difference between men and women. As mentioned earlier, some patients show mild or invisible results, but patients will still appear in their offspring. This phenomenon is related to the "semi-dominant inheritance": the disease has two copies of the disease-causing gene. When only one of the copies is mutated, the symptoms are mild and both are mutated and the symptoms are severe. There may be other reasons that affect the severity of the symptoms, which has caused some confusion in judging family history.

Inheritance of ichthyosis vulgaris

Below we discuss the risk of inheriting the disease to the next generation when a patient with ichthyosis vulgaris is having offspring in several cases.

The first case: the father is the patient [only one gene copy has been mutated (heterozygous)], the mother is a normal person, and the probability that the offspring is the patient is 2/4 = 50%

Case 2: The father is a patient [mutation of both gene copies (homozygous)], the mother is a normal person, and the probability that the offspring is sick is 4/4 = 100%

The third case: the father is the patient (heterozygous), and the mother is the patient (heterozygous). The probability that the offspring is a patient is 3/4 = 75%

The fourth case: the father is a patient (homozygous) and the mother is a patient (homozygous). This situation is simple to analyze. Neither parent has a normal gene, and it is impossible for the offspring to inherit the normal gene. Therefore, the probability that the offspring is a patient is 100%.

Summary: In real life, most patients are heterozygous, and only one copy of the gene is mutated. Therefore, the first case is the most common, and the third case is also possible. The second and fourth are rare. According to the analysis, if the heterozygous patient marries a normal person, the probability of the offspring's genetic disease is 50%, and if the same heterozygous ichthyosis patient is married, the probability of the offspring's disease will increase to 75%. It should be noted that some mild ichthyosis vulgaris "seems" to be asymptomatic, but future generations will show it. ^[1]

Sex-linked hereditary ichthyosis vulgaris is relatively rare. Because the disease's gene is on the X chromosome, it is only found in men and can develop after birth or in infancy. The skin lesions are slightly different from the upper type. The scales are large and noticeable. They are yellow-brown or dirty black with large fish scales. The skin is dry and rough and often spreads throughout the body. The armpits and elbows can also be affected. If the face is affected, it is limited to the front of the ear and the side of the face. Keratosis of the hair follicles generally does not occur. The distance between the palm and the palm is normal, and the skin lesions do not decrease with age, but sometimes increase sharply. Women with this disease are carriers, and generally do not develop the disease, sometimes only in the forearm and calf with thin scales. The corneal posterior wall and posterior elastic layer film may have small turbid spots, which does not affect vision.

Sexually linked hereditary ichthyosis is slightly different from the upper type, with large and prominent scales, yellowish brown or stained black large fish scales, dry and rough skin, often throughout the body, armpits, elbows, etc. can also be affected, and the abdomen is more than the back Especially heavy. If the face is affected, it is limited to the front of the ear and the side of the face. Keratosis of the hair follicles generally does not occur. The distance between the palm and the palm is normal, and the skin lesions do not decrease with age, but sometimes increase sharply. Women with this disease are carriers, and generally do not develop the disease, sometimes only in the forearm and calf with thin scales. The corneal posterior wall and posterior elastic layer film may have small turbid spots, which does not affect vision.

The genetics of sex-linked inheritance ichthyosis vulgaris have the following characteristics: 1. There are far more male patients than female patients in the population, and there are often only male patients in the family; 2. The parents are disease-free, the son may be affected, and the daughter is not affected; the son If it happens, the mother must be one of the carriers, and the daughter has a 1/2 probability of being a carrier; 3. Brothers, grandfathers, uncles, cousins, nephews, etc. of male patients may also be patients; 4. If women are patients His father must be a patient, and his mother must be a carrier. According to the characteristics of genetics, if men are patients with sex-linked ichthyosis, it is best to choose to have a boy, so that the inheritance of the offspring can be cut off, and future children will not suffer the inheritance. If there is a patient with sexually-linked ichthyosis in the family of the woman, it is recommended to go to the relevant medical department for prenatal consultation and testing during pregnancy. It is found that if it is a girl's gene carrier or a male's gene abnormality, the pregnancy can be terminated. There is only one pair of sex chromosomes, and more studies have been done so far. The genetic abnormalities of sex-linked ichthyosis have also been basically identified. Now, medical departments have carried out prenatal testing research. ^[2]

Everything has a cause, and so does disease. What is the cause of ichthyosis vulgaris? In fact, it is a genetic disease. The so-called genetic disease is a disease caused by changes in genetic material. As we all know, human genetic material is DNA, in a more popular way, genes. Ichthyosis vulgaris is a disease caused by mutations in genes. This is how modern science views ichthyosis. Nearly 20 FLG gene mutations have been reported to cause ichthyosis vulgaris, and these mutations are population-specific. Foreign FLG gene mutation sites and distribution: 2282del4, R501X (USA); R1474X, 5360delG, 6867delAG, 11029delCA, 11033del4, Q3683X, 7267delCA, R2447X (Europe); S2889X, S3296X (Japan); Q2417X, E2422X, R4307X, 441delA 1249insG, 7945delA (Chinese Singaporean).

Newly discovered mutation sites (China): Q1745X, Q1790X, G2788X, Q2417X, E2422X, R2447X, R3657X.

Outlook: Some people may think that genetic disease is a rare disease that is caused by abnormal changes in one of the many genetic genes in the human body. This view may have been correct 20 years ago, but the considerable progress in understanding human genes is changing doctors' thinking about the cause of disease. Today, we already know that almost all the diseases that plague humans are related to the genes they have at birth. People have gradually entered the era of genetic medicine. Although it is still in its infancy, with the success of the Human Genome Project and countless other research results, in the next 20 years, genetic medicine will make an outstanding contribution to future human health.

[Histopathology]

Mild to moderate keratinization, the granular layer becomes thin or absent. Keratinous plugs can be seen in the follicular foramen and sweat glands, the sweat glands and sebaceous glands are atrophied, and the dermis is normal.

Clinical symptoms:

(1) Squamous keratinized scales dominated by limb extension, heavy in winter and light in summer.

(2) Acne with follicular keratosis (perikeratosis). The palms and ridges are many and disordered and deep. Different degrees of palmar plantar keratosis are often present.