What is solar purpura?
The term “purpura” refers to the appearance of reddish or purple spots on the skin. These discolored spots are caused by bleeding under the skin. Solar purpura refers to purpura that occurs due to long term exposure of skin to sunlight. Bleeding occurs due to a weakening of the blood vessels present in the dermis layer of the skin. Solar purpura is most commonly seen in the elderly.
The blood vessels in the elderly are more susceptible to bleeding due to age-related changes as well as damage caused by long term exposure to the sun. Even a slight injury to the skin is capable of causing bleeding. Due to the higher incidence of solar purpura in the elderly, this condition is also sometimes referred to as senile purpura or actinic purpura. Solar purpura is not the same as sunburn.
Read more on sunburn.
Prolonged exposure to sunlight may also cause skin cancer. However, solar purpura and skin cancer are entirely different conditions. Unlike skin cancer, solar purpura is a harmless skin condition but can cause significat emotional distress. Cosmetic changes in the skin may especially affect women, who may try different treatments in order to remove the skin blemishes. However, this is unnecessary since the skin patches usually resolve on their own. In fact, the “treatments” could do more harm to the skin.
Signs and Symptoms
The main sign of solar purpura is the appearance of purple or red skin patches. The following are some of the common features of the skin patches in solar purpura:
Discoloration of the skin
Bleeding from blood vessels lying in the dermis causes the appearance of dark patches on the overlying skin. These patches are initially red in color. Over time, the color of the skin patches changes from red to purple or blue color. Eventually, the skin patch may acquire a black color. These patches are of irregular shape, and are similar to those caused by bruising of the skin. Usually, there is no itching or pain associated with these discolored skin patches.
Localized skin patches
The discolored skin patches in solar purpura are most commonly located in areas of the skin that are maximally exposed to sunlight. For example, skin patches in solar purpura typically appear on the back of the hand (extensor surface), forearms, face, and neck. Fingers are usually not involved.
Purple to yellow rash
The skin patches in solar purpura resolve on their own within 1-3 weeks. No treatment is usually required. However, even after the disappearance of the red or purple skin patches, the affected skin areas may continue to exhibit a yellowish tinge for a few weeks to a few months.
How does solar purpura form?
The skin forms the outermost protective covering of the human body. As we age, the barrier function of the skin gets compromised due to a progressive loss of collagen tissue. Loss of collagen also weakens the blood vessels that lie within the skin tissue. This age-related weakening of the skin is commonly referred to as dermatoporosis. Chronic exposure to sunlight also contributes to the process of dermatoporosis.
This could be one of the reasons why elderly people who spent many hours of their early years in the sun seem to have relatively more skin blemishes and wrinkles.The damage caused to the skin by chronic exposure to sunlight is due to the presence of ultraviolet radiation in the sunlight. The longer the extent of exposure to sunlight, the more the damage to the skin.
However, the extent of exposure to sunlight required to damage the skin depends on the color of the skin. For example, light-skinned individuals tend to get skin damage even upon moderate exposure to sunlight over a long period of time. Damaged skin cannot provide mechanical stability to the blood vessels in the skin. This makes the blood vessels in the skin prone to damage even with the slightest of impacts.
Causes of Solar Purpura
Chronic exposure to sunlight
As the name suggests, solar purpura is predominantly caused by chronic exposure to sunlight. The loss of collagen due to aging also contributes to the development of this condition. Both the skin and the blood vessels within the skin become weak, and can get injured upon the slightest of impacts. Bleeding from the blood vessels in the skin results in the appearance of the characteristic red or purple skin patches.
When the skin and the blood vessels within the skin become very fragile, even the slightest of injuries can cause bleeding. In many cases, the affected individual may not even be aware of the slight injury that resulted in the appearance of red patches on the skin. Inflammation may also be absent at the site of the minor injury. This further masks the injurious event.
As mentioned previously, the loss of collagen due to aging also contributes to the mechanism of solar purpura. As many as 10-12% of the individuals affected by solar purpura are over 50 years of age. Advancing age and increased exposure to sunlight increase the risk of developing solar purpura.
Medications such as aspirin can worsen the skin condition caused by solar purpura. However, on their own, medications do not cause solar purpura.
Diagnosis of Solar Purpura
Solar purpura is typically diagnosed through visual examination of the characteristic red or purple skin patches on the skin. Biopsy of the skin may be also be conducted in order to confirm the diagnosis of solar purpura and exclude other similar conditions. Atrophy of the skin may become evident upon microscopic examination of the skin tissue.
Treatment of Solar Purpura
The skin condition that is characteristic of solar purpura usually resolves on its own without any treatment. Skin creams containing vitamin K may help in treating the skin patches caused by solar purpura. Also, tretinoin can reverse the skin damage caused by exposure to sunlight.
The following are some of the measures that may help in preventing the occurrence of solar purpura:
- Reducing exposure to sunlight: One should limit the amount of time one spends in the sun. Wearing clothes that limit exposure of skin to direct sunlight may also help.
- Apply sunscreens: Use of sunscreen can limit the damage caused by direct exposure to intense sunlight. Therefore, sunscreens should be used from a young age to prevent long term damage to the skin by chronic exposure to ultraviolet radiation in sunlight. Even if a person has already developed solar purpura, sunscreen use should be continued to limit the damage to the skin.
- Using skin moisturizers: Dry skin is more susceptible to damage by exposure to sunlight. Therefore, use of skin moisturizers may help limit the skin damage upon exposure to sunlight.