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Solar keratosis
Health Guide
What is solar keratosis

Solar keratosis, also known as actinic keratosis refers to an abnormal skin growth on areas frequently exposed to the sun. This means, the areas of skin that are commonly affected are the face, ears, bald scalp, neck, shoulders, back of hands, arms, and lips.

Solar keratoses are not skin cancers but because they are precancerous growths they have the potential to develop into malignant skin cancers. It has been estimated that approximately 20% of active lesions that look more red and tender than the rest will progress into squamous cell carcinomas. If keratoses are detected and treated early, they are usually harmless. If they are not treated in the early stages, they can spread with tendency to invade surrounding and sometimes deeper tissues, causing damage.

Symptoms

The skin lesion has a rough and dry texture, localised on the sun-exposed area. It may take the form of different colours e.g grey, pink, red, tan or the same colour as the skin. The lesion may initially look flat, scaly or crusty. As it slowly develops, it may be slightly raised and the surface becomes hard, wart-like and has a sandpapery feel. Keratosis refers to the excessive keratin that is produced by the skin as a result of sun damage. Sometimes lesions may produce so much keratin that a ‘horn’ forms and protrudes from the surface of the skin.

Solar keratoses are difficult to see, thus are often recognised by touch. Occassionally, they itch or produce a pricking or tender sensation. These lesions are found scattered throughout the commonly affected skin sites, because often, there will be several keratoses appearing at the same time.

What caused the condition?

Sun exposure is the cause for almost all the solar keratosis. Since the lesion grows slowly, this means that repeated, prolonged sun exposure will cause skin damage and this will accumulate to develop into a keratosis. Sunlight contains the harmful UV-B rays, which reach the surface of the earth, and they can bounce off sand, snow and other reflective surface. This means that everyone is exposed to the sun no matter what the climate is. These rays can cause an irreversible structural change in DNA of skin cells (keratinocytes) which initiates the tumourigenic process.

UV-B rays also alter our immune responses because over exposure of the skin to these rays will cause the skin (Langerhans) cells to change their shape and alter their function. These Langerhans cells are in the epidermis (top) layer of the skin and are involve in presenting antigens to T-cells (cells in the immune system). As a result of the UV damage to these cells, they cannot carry out their normal surveillance function and so there’s an immune suppression effect on the skin. This does not affect other similar cells which are resistant to UV damage, therefore there’s a local imbalance in T-cell function. It has been suggested that this immune suppression may cause an individual to be more susceptible to infection and development of skin cancer.

Epidemiology

It is believe that one in six people will develop actinic keratosis in their lifetime. Older people are more at risk of developing a keratosis because sun exposures are accumulated and increases with the years. However, keratoses are now appearing in young people in their early 20’s because they spend too much time in the sun with little or no protection. This also means that skin cancer is becoming more common among youngsters.

Those who have fair skin and those with red or blonde hair are also at a higher risk because their skin have less protective pigment (melanin) and therefore are more susceptible to sunburn. Africans rarely have these lesions because they have darker skin, which means there is more melanin present. People who work outdoors, e.g farmers and construction workers or those who love outdoor sports are at the highest<

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