Polymorphous Light Eruption : PMLE

Polymorphous light eruption (PMLE) is a type of skin rash that can occur after exposure to sunlight or artificial light.
PMLE typically appears as small red bumps on the skin that may itch or burn. The rash usually goes away on its own within a few days or weeks but it can occasionally last for months.
PMLE is often caused by UVA or longer wavelength UVA and UVB and can therefore be induced by glass or by thin clothing.

PMLE symptoms

This is a common intermittent skin reaction to UV exposure that may represent a delayed hypersensitivity response to UV-induced skin antigens.
It affects up to 20% of the population in temperate zones, especially women under 30 years of age.
PMLE presents with a symmetrical, non-scarring, pruritic papular rash on sunexposed sites within hours or days after exposure to strong sunlight.
Large and small papules, papulopustules, and vesicles may appear, sometimes merging into edematous plaques.The rash is transient and goes away within a few days, but may persist if exposure continues.
Chronically exposed areas such as the face are often spared.The rash is usually confined to spring and early summer and often improves as summer progresses.The juvenile spring rash is probably a variant of PMLE and usually presents as itchy blisters on boys' light-exposed props after sun exposure .
Tolerance to UV radiation usually develops, so the disease becomes more common in spring.

The history and clinical features of PMLE generally distinguish it from other photodermatoses.

Photoallergic contact dermatitis can be difficult to rule out if there is a history of sunscreen use and patch testing/photopatch testing is being considered.

Cutaneous lupus should be considered, and a minority of PMLE patients may develop lupus several years later.
Lesion histology can support the diagnosis.
If diagnostic uncertainty persists, a phototest can be performed using monochromatic irradiation or a solar simulator.

Treating polymorphic light eruption is easy
Most patients can control their own rash with sensitive sun exposure and regular use of highly protective UVA/UVB sunscreens.
Mineral sunscreen is the best sun cream for polymorphic light eruption since it does not contain organic components or additives, which can irritate some people. Any sunscreen (mineral or chemical) will suffice. The most critical factor is that the sunscreen provides adequate UVA protection and that patients enjoy using it.
Strong topical corticosteroids or brief oral corticosteroid therapy are usually effective in treating an acute attack.