WHAT IS ICHTHYOSIS?Ichthyosisis a collective name for a number of hereditary skin disorders, which are characterized by dry and flaky skin with thickening of the stratum corneum. The name comes from the Greek word 'ichthys', which means fish. The rough skin of someone with ichthyosis resembles that of a fish. The disease is also called fish skin or scaled skin. The distinction between the various forms of ichthyosis is determined by the external symptoms and the way in which the disorders are inherited.
The main forms of ichthyosis are:
- ichthyosis vulgaris
- X-linked recessive ichthyosis
- lamellar ichthyosis
- congenital bullous ichthyosiform erythroderma.HOW DOES ICHTHYOSIS OCCUR?The various forms of ichthyosis are based on specific disorders in the keratinization of epidermal cells. The abnormal keratinization is due to hereditary defects in several skin cell genes.
In ichthyosis vulgaris , the most common form of ichthyosis, the protein profilaggrin, which is necessary for normal keratinization, is missing. Ichthyosis vulgaris is inherited in an autosomal dominant pattern. This means that approximately 50% of the children of someone with this condition will also have ichthyosis. Boys and girls are affected equally often.X-linked recessive ichthyosisoccurs only in boys and men. The mother of someone with this form of ichthyosis carries the abnormal gene without showing any symptoms herself. Within a family, the condition is therefore always passed on via the women to the male offspring. The cause of this keratinization disorder is the lack of the enzyme steroid sulfatase, for which the gene is located on the X chromosome. Hence the name X-linked ichthyosis. The enzyme steroid sulfatase plays a role in the keratinization of skin cells. If the enzyme is missing, the keratinized cells remain attached to each other for longer, causing the stratum corneum to thicken.Lamellar ichthyosisis divided into three subtypes. Two of these subtypes are inherited in an autosomal recessive pattern. This means that the condition only manifests in someone whose parents both carry the abnormal gene. The parents themselves do not necessarily have ichthyosis. In addition, there is a very rare autosomal dominant subtype.
In one of the autosomal recessive subtypes, the enzyme transglutaminase-1 is absent. This enzyme plays an important role in the normal keratinization of skin cells.
In the other autosomal recessive subtype, the activity of the enzyme transglutaminase-1 is normal. The cause of this form of ichthyosis is not yet known. The same applies to the autosomal dominant form of lamellar ichthyosis.
Congenital bullous ichthyosiform erythroderma is based on a hereditary defect in one of the genes for certain keratin proteins. Keratin proteins are essential for the structure and keratinization of skin cells. This form of ichthyosis is inherited autosomal dominantly, following the same pattern as ichthyosis vulgaris.
Besides the aforementioned forms of ichthyosis, there are several other very rare forms. Ichthyosis can also develop later in life as a non-hereditary condition.
The acquired form is usually due to internal diseases or malignant conditions.WHAT ARE THE PHENOMENA?Ichthyosis vulgarisThe symptoms of ichthyosis vulgaris are not present at birth. After the child is a few months old, but sometimes later, a grayish scaling develops on the skin of the trunk, arms, and legs. The entire skin appears very dry. However, the skin in the armpits, elbows, and knees always appears normal. The skin lesions usually improve during the summer and worsen during the winter. This form of ichthyosis is often associated with atopic eczema. The creases in the palms of the hands are usually noticeably accentuated, as are the folds in the soles of the feet. Ichthyosis vulgaris is not associated with abnormalities in other organs.X-linked recessive ichthyosisX-linked recessive ichthyosis occurs only in boys and men. A few months after birth, brown scaling develops on the trunk, arms and legs. The skin lesions are often very pronounced on the neck. In severe cases, dark brown, scaly thickenings are present on the skin. The entire skin gives a dried out appearance. The armpits, backs of the elbows and backs of the knees sometimes show scaling to a greater or lesser extent, in contrast to ichthyosis vulgaris. The palms of the hands and soles of the feet show no abnormalities. Sometimes X-linked recessive ichthyosis can be accompanied by clouding of the cornea. This does not adversely affect vision.
In children with X-linked recessive ichthyosis, undescended testicles are quite common. In women pregnant with a child with X-linked recessive ichthyosis, delivery can sometimes be difficult.Lamellar ichthyosisThe various forms of lamellar ichthyosis can be severe at birth. In that case, the child has a smooth, tight layer of skin covering its entire body. This is called a collodion baby. Over time, the covering layer cracks open and then disappears.
In the form of lamellar ichthyosis in which the enzyme transglutaminase-1 is absent, the entire skin is covered with coarse, dark brown scales. Between the scales, the skin has a slightly cracked appearance. The entire skin is usually affected, including the scalp and face. Due to the facial abnormalities, the lower eyelids may be everted (ectropion). Sometimes, nail abnormalities may be present, and hair growth on the head may be reduced.
The other autosomal recessive form of lamellar ichthyosis is known as congenital non-bullous ichthyosiform erythroderma or erythrodermatous lamellar ichthyosis. This form can present at birth as collodion in the baby, but also as redness of the entire skin (erythroderma; erythros = red, derma = skin). Over time, the redness diminishes. The scaling is less coarse than in the first-mentioned form. The skin lesions occur all over the body. Ectropion can also develop in this form of lamellar ichthyosis. Sometimes the palms of the hands and soles of the feet are thickened by a smooth callus, and nail abnormalities and reduced hair growth may occur.Congenital bullous ichthyosiform erythrodermaAt birth, the entire skin is red and exhibits superficial peeling or blistering. Over time, the redness and blistering gradually diminish, and a thick keratinization of the skin develops.
This keratinization is most pronounced in the neck, armpits, backs of the elbows and knees, and in the groin. Blisters can still develop later in life, for example, due to friction. The skin may give off a rancid odor. The palms of the hands and soles of the feet are sometimes thickened by a callus.HOW IS THE DIAGNOSIS MADE?The diagnosis of ichthyosis is made primarily on the basis of the skin manifestations. Sometimes it can be difficult to distinguish ichthyosis vulgaris from X-linked recessive ichthyosis. The way in which the skin condition is inherited within the family can help make this distinction. The diagnosis of X-linked recessive ichthyosis can be made with certainty by determining the enzyme steroid sulfatase in the blood. The diagnosis of lamellar ichthyosis with the absence of transglutaminase-1 can be confirmed by examining cultured skin cells. The enzyme cannot be demonstrated in cell cultures. Microscopic examination of a skin sample is usually not helpful in making the diagnosis, except in congenital bullous ichthyosiform erythroderma.WHAT IS THE TREATMENT?For ichthyosis vulgaris, treatment consists of thoroughly moisturizing the skin daily. This can be done with greasy creams or a urea-containing cream. The use of bath oil can be beneficial.
X-linked recessive ichthyosis is treated in the same way. If the skin condition is very severe, treatment with acitretin can also be initiated.
Lamellar ichthyosis will usually have to be treated with acitretin. Applying greasy or urea-containing creams is necessary, but often not sufficient.
Congenital bullous ichthyosiform erythroderma is also treated with emollient creams and acitretin, but great caution must be exercised. If the acitretin dose is chosen too high, extensive blistering can occur.WHAT ARE THE OUTLOOK?The symptoms of ichthyosis will remain present throughout life. However, the course can vary. Ichthyosis vulgaris may diminish somewhat with later age, and the same applies to X-linked recessive ichthyosis. Lamellar ichthyosis remains a lifelong problem. Usually there is no improvement.
Congenital bullous ichthyosiform erythroderma will also not improve, but the tendency to blister formation diminishes with increasing age.WHAT CAN YOU STILL DO YOURSELF?Due to the very dry skin, drying soaps should not be used when washing. Long, hot showers are discouraged. Using an emulsifying oil in bathwater can improve the skin. Emollient creams should be applied consistently. It is recommended that people with ichthyosis in the family seek information about the hereditary aspects of the skin condition. In severe cases of ichthyosis, it is advisable to seek genetic counseling if they intend to have children. |
