Introduction:
Polymorphous light eruptions (PMLE) are idiopathic, sunlight, or artificial light-induced cutaneous eruptions, ranging from papulovesicular lesions to large plaques, mainly localized to the photo-exposed areas of the body. It occurs, particularly at temperate latitudes. Cutaneous eruptions occur intermittently and follow specific sun exposure or artificial ultraviolet radiation, which usually extends from minutes to hours or rarely days. The eruptions may last for days to a week after the exposure ceases. It affects individuals of all races. Polymorphous light eruptions affect women twice as frequently as men of all ages. The prevalence in the general population is inversely related to latitude, and it is most common in temperate regions. It is due to the hardening phenomenon experienced by patients residing in hot climates. The risk of developing polymorphous light eruptions is highest with Fitzpatrick's skin type 1 (fair skin), and the lowest prevalence is seen in people with skin type 4 and above (darker complexion).
What Are the Signs and Symptoms of Polymorphic Light Eruptions?
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In polymorphous light eruptions, pruritus almost always occurs within minutes, and chronic recurrent eruptions are seen on the photo-exposed sites, though some light-exposed parts may be spared.
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A burning or itchy rash may appear within a few hours or up to two to three days after exposure to sunlight. The rashes may be visible for two weeks and heal without scarring.
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The rash can be polymorphic (taking many different forms). It has dense clusters of small blisters and bumps. The affected area is inflamed and has raised rough patches.
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Lesions commonly occur in early summer and gradually improve as the season progresses due to the hardening effects. Sun exposure for a few minutes to several hours is required to initiate the development of lesions, but the lesions become visible only several hours after sun exposure.
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Typically, affected sites include the bridge of the nose, malar areas of the cheeks, the tip of the chin, side and back of the neck, upper chest, dorsum of hands, dorsolateral aspects of the arms, front and back of the legs and dorsum of the feet. Lesional distribution and morphology vary with patients.
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Patients may also experience fever and chills.
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Polymorphic light eruptions can persist for many days and worsen if the affected area is further exposed to sunlight before the previous eruption is resolved.
What Is the Cause of Polymorphic Light Eruptions?
The exact cause of polymorphic light eruptions is not known. People sensitive to sunlight or ultraviolet radiation from the sun or other sources are called photosensitive. Such people are more prone to polymorphous light eruptions. Genetic susceptibility is seen in 15 to 45 % of the cases with a positive family history. Polymorphic light eruptions are primarily caused by UVA, UVB alone, or UVA and UVB together. It is seldom caused by visible light.
How to Diagnose Polymorphic Light Eruptions?
The diagnosis of polymorphic light eruptions is made based on the physical examination and the questions that the doctor will ask the patient. The other tests to confirm the diagnosis are:
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Skin Biopsy - A sample of tissue from the skin rash is removed and sent to the laboratory for testing.
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Photo Testing - Small areas of the patient’s skin is exposed to the measured amounts of ultraviolet A and B light under the supervision of a specialist to reproduce the problem. If the skin reacts to the radiations, the patient is considered photosensitive to sunlight and might have polymorphic light eruptions.
How to Prevent Polymorphic Light Eruptions?
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Avoid midday sunlight exposure from 10 am to 2 pm.
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Use sunscreen. Apply a broad-spectrum sunscreen 15 minutes before going out. Apply a copious amount of sunscreen and apply it every two hours.
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To protect themselves from the sun, people should wear clothing that covers their arms and legs.
What Are the Complications of Polymorphic Light Eruptions?
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Depression and anxiety.
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The risk of vitamin D deficiency due to lack of sun exposure.
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Avoidance of outdoor physical activities due to the concern of excessive sun exposure.
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Emotional distress.
What Is the Differential Diagnosis of Polymorphic Light Eruptions?
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Solar Urticaria - It is a sun-induced allergic reaction characterized by inflamed, raised, and itchy bumps that appear and disappear on the skin.
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Seborrheic Dermatitis - It is a skin condition that affects any part of the body and is characterized by an itchy rash on the scalp.
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Lupus Erythematosus - It is an autoimmune inflammatory disorder that affects multiple organs of the body. One of the symptoms is the appearance of a rash on the body parts exposed to the sunlight, like the neck, face, or upper chest.
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Photoaggravated Atopic Dermatitis - It is a subtype of atopic dermatitis provoked by exposure to ultraviolet radiation.
What Are the Treatment Options for Polymorphic Light Eruptions?
Polymorphic light eruptions usually do not require treatment as the rash often goes away on its own in a period of ten days.
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If the symptoms are severe, topical or oral steroids are prescribed for a short duration.
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In the event of repeated attacks, a prophylactic course of low-dose PUVA therapy (Phototherapy) using 311 nm UVB is the treatment of choice. It mimics the increased exposure a person may experience during the summer.
What Self-Care Measures Can Ease the Symptoms of Polymorphous Light Eruptions?
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Use Cold Compresses - Taking a cool bath or applying a cloth dampened with cool tap water to the affected area can ease the symptoms.
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Apply Anti-itch Cream - Non-prescription creams containing at least one percent of Hydrocortisone can be applied as it relieves the symptoms.
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Leaving Blisters Alone - Blisters should be left intact to speed healing and avoid infections. People can lightly cover the blisters with gauze.
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Protect Rash From Sun Exposure - Always cover the rash before going out to protect it from further sun exposure.
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Take Pain Killer - Over-the-counter pain reliever can be taken as it helps reduce pain and inflammation.
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Take Antihistamines - Oral antihistamines are very helpful if itching is unbearable.
Conclusion:
The polymorphic light eruption is a skin condition triggered by sun exposure. It is seen on the body parts that are exposed to ultraviolet light. It is not a contagious disease. For most patients, the symptoms improve in a few days, but the condition can be lifelong as well. That is why people prone to developing this condition are advised to follow the necessary precautions.
