Dermatology - Polymorphous Light Eruption (PMLE)

Dermatology - Polymorphous Light Eruption (PMLE) 
A collection of varied, idiopathic, acquired, acute recurring eruptions that are a delayed reaction to UV radiation are together referred to as PMLEs. The most prevalent type of photodermatitis, PMLE often appears in the third decade of life. It is more prevalent among lighter-skinned people and women than in men. Among American Indians, both in North and South America, actinic prurigo is a hereditary type.
 
Early spring and summer are the times for lesions to appear. These include erythematous macules, papules, plaques, and vesicles. Nonetheless, there is only ever one form of eruption in each patient, most often papular or papulovesicular. After exposure, PMLE often manifests within hours and lasts for seven to ten days. Often, the eruptions stop occurring by the end of the summer, indicating a "hardening." Paresthesia (tingling) and pruritus (which may occur before the rash appears) are the symptoms.
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The most common kinds are papulovesicular and papular. Urticarial plaques, or plaques, are far less prevalent. Pink to crimson lesions are seen. The eruption most commonly affects the forearms, arms, chest, and V area of the neck, sparing habitually exposed areas (the face and neck). If the face has never been exposed to the sun before, lesions could still develop there.

When an eruption has a delayed beginning, distinct morphology, histopathologic abnormalities that rule out lupus erythematosus, and a history of the eruption disappearing over a period of days, a diagnosis is made. To rule out lupus in patients with plaque-type PMLE, a biopsy and immunofluorescence tests are required. Photo-testing is carried out using UVA and UVB light.
Test sites are exposed to UVB and UVA radiation on a daily basis for a duration of one week to ten days, with gradual increases in UV exposure. A PMLE-like eruption appears in the test sites in almost 50% of patients, supporting the diagnosis. The type of PMLE in that specific patient is mirrored in the eruption at the test location.

Although they are not always effective, sunscreens—even the strongest UVA and UVB sunscreens—should always be attempted first. Oral prednisone (20 mg/day) administered two days prior to and two days during exposure, as well as systemic β-carotene (60 mg three times a day) for two weeks prior to exposure may also prevent eruptions. A few days prior to exposure, 40 mg of intramuscular triamcinolone acetonide is injected to inhibit an eruption.