ichthyosis

Overview of ichthyosis

Ichthyosis is a group of skin conditions that result in dry, itchy skin that looks flaky, rough, and red. Symptoms can range from mild to severe. Ichthyosis can only affect the skin, but some forms of the disease can also affect internal organs.

Most people inherit ichthyosis from their parents through a mutated (altered) gene. However, some people develop a form of acquired (non-genetic) ichthyosis due to another medical condition or certain medications. While there is currently no cure for ichthyosis, research is ongoing and treatments are available to help manage symptoms.

The outlook for people with ichthyosis varies depending on the type of disease and its severity. Most people with ichthyosis need lifelong treatment to make the disease more manageable.

Who gets ichthyosis? 

Anyone can get ichthyosis. The disease is usually transmitted from parents; however, some people may be the first in the family to develop ichthyosis due to a new gene mutation. Other people develop an acquired (non-genetic) form of ichthyosis, which results from another disease or drug side effect.

Types of ichthyosis

There are over 20 signs of ichthyosis, including those that occur as part of another syndrome or condition. Doctors can determine the type of ichthyosis by looking for:

• Gene mutation.
• Inheritance model by analyzing family trees.
• Symptoms, including their severity and which organs they affect.
• Age when symptoms first appeared.

Some types of disease that are inherited and are not part of the syndrome include the following:

• Ichthyosis vulgaris is the most common type. It usually proceeds in a mild form and manifests itself in the first year of life with dry, flaky skin.
• Harlequin ichthyosis is usually seen at birth and causes thick, scaly sheets of skin to cover the entire body. This form of the disorder can affect the shape of facial features and limit joint mobility.
• Epidermolytic ichthyosis is present from birth. Most babies are born with fragile skin and blisters covering their bodies. Over time, the blisters disappear, and peeling appears on the skin. It may have a ribbed appearance on areas of the body that curve.
• Lamellar ichthyosis is present from birth. A baby is born with a tough, transparent membrane covering the entire body called the collodion membrane. Within a few weeks, the membrane flakes off, and large dark lamellar scales appear on most of the body.
• Congenital ichthyosiform erythroderma is present at birth. Babies also often have a collodion membrane.
• X-linked ichthyosis usually develops in boys and begins around 3 to 6 months of age. Peeling is commonly present on the neck, lower face, torso, and legs, and symptoms may worsen over time.
• Variable erythrokeratoderma usually develops several months after birth and progresses during childhood. Rough, thick, or reddened patches of skin may appear on the skin, usually on the face, buttocks, or extremities. The affected areas may spread to the skin over time.
• Progressive symmetric erythrokeratoderma usually presents in childhood with dry, red, scaly skin predominantly on the extremities, buttocks, face, ankles, and wrists.

Symptoms of ichthyosis

Symptoms of ichthyosis can range from mild to severe. The most common symptoms include:

• Dry skin.
• Itching.
• Redness of the skin.
• Cracking of the skin.
• Scales on the skin of white, gray or brown color have the following appearance:
  • Small and crumbly.
  • Large, dark, lamellar scales.
  • Hard, armor-like scales.

Depending on the type of ichthyosis, other symptoms may include:

• Blisters that can burst, resulting in wounds.
• Hair loss or brittleness.
• Dry eyes and difficulty closing the eyelids. Inability to sweat (sweat) because skin flakes clog the sweat glands.
• Hearing difficulties.
• Thickening of the skin on the palms and soles of the feet.
• Skin tightening.
• Difficulty bending some joints.
• Open wounds from scratching itchy skin.

Cause of ichthyosis

Gene mutations (changes) cause all hereditary types of ichthyosis. Many gene mutations have been identified, and the nature of inheritance depends on the type of ichthyosis. Humans are constantly growing new skin and shedding old skin throughout their lives. In people with ichthyosis, the mutated genes alter the normal growth and sloughing cycle of the skin, causing skin cells to do one of the following:

• They grow faster than they drop.
• They grow at a normal rate but shed slowly.
• They shed faster than they grow.

There are different types of inheritance for ichthyosis, including:

• Dominant, which means you inherit one normal copy and one mutated copy of the gene that causes ichthyosis. The abnormal copy of the gene is stronger or "dominates" the normal copy of the gene, causing disease. A person with a dominant mutation has a 50% chance (1 in 2) of passing the disease on to each of their children.
• Recessive, which means that your parents do not have signs of ichthyosis, but both parents carry only one abnormal gene, which is not enough to cause the disease. When both parents carry the same recessive gene, there is a 25% chance (1 in 4) per pregnancy of having a child who will inherit both of these mutated genes and develop the disease. There is a 50% chance (2 out of 4) for a pregnancy to have a child who inherits only one mutated recessive gene, making her a carrier of the disease gene with no noticeable symptoms. If one parent has a recessive form of ichthyosis with two mutated genes, all of their children will carry the one abnormal gene but will usually not have noticeable signs of ichthyosis.
• X-linked, which means that the gene mutations are located on the X sex chromosome. Every person has two sex chromosomes: females usually have two X chromosomes (XX) and males usually have one X chromosome and one Y chromosome (XY). The mother always passes on the X chromosome, while the father can pass on the X or Y chromosome. The inheritance pattern of X-linked ichthyosis is usually recessive; this means that males who initially have only one X chromosome pass on a mutated X chromosome. Because of this pattern, women are more often affected, and they usually have one mutated and one normal X chromosome.
• Spontaneous, which means that the gene mutation occurs randomly without a family history of the disease.