Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE): Causes, Symptoms, Treatment

Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE), is a skin condition characterized by an itchy rash upon exposure to the sun in those individuals who have photosensitivity or sensitivity to sunlight. The rash typically appears as tiny, red bumps or as slightly elevated patches on the skin.

Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE) commonly occurs during the spring season and in early summer when the sun exposure increases. The rash commonly develops on those regions of the body which are covered during the winter season, but exposed during the summer season, such as arms, anterior side of the neck and the upper part of the chest. The likelihood of recurrent episodes decreases, as the summer progresses; however, the patient will usually have episodes of polymorphous light eruption every year after the first episode. Sometimes, the photosensitivity decreases gradually in some individuals over the years and they may no longer have recurrent episodes of PLE.

Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE) typically does not require any treatment and resolves on its own; but for severe or persistent cases, treatment is needed. Patients also need to protect their skin from sun exposure or to prevent recurring episodes of PLE.

The exact cause of polymorphous light eruption is not known. The rash develops in those individuals who have developed sensitivity to sunlight, especially ultraviolet (UV) rays from the sun, tanning beds/tanning lamps. This photosensitivity causes sunlight-induced activity of immune system, which results in inflammation and rash.

• Women are more prone to develop Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE).
• Fair skinned individuals are at an increased risk for developing this disorder.
• Adolescents or young adults are more likely to develop the first episode of PLE.
• Having a family history of polymorphous light eruption increases the likelihood of having this disorder.

• Formation of small bumps in dense clusters.
• Presence of elevated rough patches.
• Burning or itching sensation.
• Redness.
• Blistering is present.
• Swelling may be present.
• Rarely, symptoms like fever, chills, nausea or headache can be present, which are more from the related sunburn than PLE.
• Serious symptoms include extending of the rash, pain and fever.

Physical exam is most of the times sufficient to make a diagnosis of Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE). Tests done to further confirm the diagnosis include:

• Blood tests to rule out other conditions.
• Skin biopsy where a scraping of the rash is taken and sent to testing to rule out other rash producing conditions.
• Phototesting is done to exclude other light-induced disorders, such as solar urticaria, chemical photosensitivity and lupus rash.

Treatment for Polymorphous Light Eruption (PLE) or Polymorphic Light Eruption (PMLE) is not usually needed, as the rash usually resolves on its own within a week or so. Treatment for severe and persistent cases comprises of:

• Topical anti-itch ointments or creams, which contain 1% hydrocortisone. For pain or itching, stronger corticosteroid creams are prescribed.
• OTC pain relievers, such as acetaminophen, naproxen, ibuprofen etc., help with the pain, redness and itchiness.
• Light therapy or phototherapy helps in preventing seasonal episodes of PLE. In this treatment, the skin is exposed to small amounts of UVA or UVB rays, which will decrease the skin’s sensitivity to light.
• PUVA or psoralen plus ultraviolet A is a type of light therapy, which combines UVA with a medicine known as psoralen, which increases the skin’s sensitivity to this light. Side effects include headache, nausea and itching.
• Conservative measures, such as application of cold compresses or a cool bath, helps in relieving the symptoms.
• Never rupture the blisters otherwise it will cause delayed healing and infection. Cover the blisters with gauze.
• Try to avoid stepping out in the sun between 10 a.m. to 4 p.m. when the sun rays are its severest.
• Always apply sunscreen with a minimum SPF of 15 about 20 to 30 minutes before going outdoors.
• Always wear protective clothing, such as broad-brimmed hat or long sleeved shirts etc., to give protection from the sun.