What is Ichthyosis?
Ichthyosis is a family of generalised, genetic skin disorders. The word comes from Ancient Greek ιχθύς, „fish“. Ichthyosis is characterised by dry, thickened, scaling skin and is not contagious. The different ichthyoses have a wide range of severity and associated symptoms.
To date there is no cure for ichthyosis but the condition of the skin may be improved by intensive care. Sometimes the skin condition improves during the course of life.
Ichthyosis vulgaris is the most common hereditary skin disease and one of the most common hereditary diseases of all. It is usually a mild ichthyosis and becomes apparent by dry, rough, scaling skin and occasional itching.
About one in 300 persons is affected by ichthyosis vulgaris.
Ichthyosis has existed as long as mankind has existed, and even dogs can have ichthyosis.
It is thought that some individuals of the Merovingian dynasty, and also Siegfried, the hero in the German medieval Nibelungenlied had ichthyosis.
The first scientific, documented case is of Edward Lambert, who was introduced to the Royal Society in London on May 16th 1731. His parents were not affected, but he is described as having Ichthyosis Hystrix. He married and passed on his condition to six of his offspring, however his life span was not diminished by his ichthyosis because he was aged 90 when he died in an accident in 1806.
The characteristic symptom of all the ichthyoses is a dry, thickened epidermis (outermost layer of the skin) and visible scaling. Some types of ichthyosis show reddened skin and most people with congenital ichthyosis cannot sweat. Ichthyosis with blistering (EHK) and ichthyosis with associated findings (e.g. Netherton's syndrome, Sjögren-Larsson syndrome) are rare.
The skin is alive. It is constantly renewing itself, dying and shedding.
The cuticle consists of several sub-layers and cells are born in the deepest layer called stratum basale. These cells migrate outward, flattening and dying as they go and finally arriving at the surface layer called the corneal layer.
The corneal layer consists of thin layers of flat dead cells containing keratin, a stringy, fibrous protein which reinforces the corneal layer. Fat is stored between the cells and this makes the skin water-repellent. The corneal layer also helps to regulate the water balance of the body.
The corneal layer is constantly shedding in microscopically small pieces and the whole process is called keratinization. This process of keratinization renews the skin approximately every 4 weeks.
In healthy skin, the production of new cells and the shedding is constant, but with ichthyosis the shedding is disturbed and visible scales are formed. Proliferation-hyperkeratinization occurs in some of the ichthyoses where the cells are formed too rapidly whilst in others the skin's natural shedding process is slowed or inhibited. In X-linked Ichthyosis and Ichthyosis Vulgaris the skin cells reproduce at a normal rate but do not shed as quickly, and it is this which produces a build-up of scales.
The skin is the body’s largest organ and therefore ichthyosis affects the sufferer accordingly. With moderate ichthyosis the affects are less, and especially in winter the skin is dry, sometimes scaly and itching may occur. With severe ichthyosis (congenital ichthyosis) more scales are formed and the symptoms are more extreme.
Ichthyosis disturbs the normal function of the skin and because sweating is affected, the body cannot regulate internal temperature normally and overheating occurs. It is important to always have water at hand in the summer and whilst taking exercise. Swimming is often a very suitable exercise, because of the cool water.
With EHK the skin is very fragile and easily forms blisters. If the soles of the feet are affected just a short walk may result in sore and aching blisters. This is an issue for a baby learning to walk. Therapeutic horseback riding may help by training muscles to find balance and to learn rhythm without putting pressure on the soles of the feet.
A physician can often diagnose ichthyosis just by looking at the skin.
In some cases, a blood test or a skin biopsy will be taken to confirm the diagnosis. A small piece of skin is extracted in a biopsy and examined under a microscope.
Family history is also very useful and most recently genetic testing is helpful in making a diagnosis.
Ichthyosis is not more or less common in any ethnic group.
The routine of skin care is very time consuming, with daily bathing and moisturising and regular exfoliation of the build up of scales.
Treatments take the form of topical application of moisturisers which include ointments, creams, lotions and emollient oils.
Retinoids may be used for some conditions.
Careful exposure to sunlight may improve the condition.
There are several forms of ichthyosis. Most forms are genetic conditions, which can be divided into two main groups:
Noncongenital (vulgar) ichthyosis is not visible at birth; it develops within the first months after birth. Congenital ichthyosis is present at the day of birth.
- Ichthyosis vulgaris (Autosomal Dominant Ichthyosis vulgaris, ADI)
- X-linked ichthyosis (XRI)
- Ichthyosis lamellaris
- Bullous Ichthyosis (Epidermolytic hyperkeratosis, EHK)
- Harlequin Ichthyosis
- Netherton's syndrome
- Sjögren-Larsson syndrome
Ichthyosis acquisita is acquired not inherited, it is a manifestation of other diseases.