Polymorphous light eruption

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Polymorphous light eruption (PMLE) is a common photodermatosis characterized by an abnormal skin reaction to ultraviolet (UV) radiation. It typically manifests as an itchy rash that appears on sun-exposed areas of the skin.

Presentation

PMLE usually presents within hours to days after exposure to sunlight. The rash can take various forms, including papules, vesicles, and plaques. Commonly affected areas include the neck, arms, and the back of the hands. The rash is often accompanied by pruritus (itching) and may persist for several days before resolving.

Pathophysiology

The exact cause of PMLE is not fully understood, but it is believed to involve an abnormal immune response to UV radiation. This response leads to the release of inflammatory mediators and subsequent skin changes. Both UVA and UVB radiation can trigger PMLE, although UVB is more commonly implicated.

Diagnosis

Diagnosis of PMLE is primarily clinical, based on the characteristic appearance of the rash and its temporal relationship to sun exposure. A detailed patient history and physical examination are essential. In some cases, a skin biopsy may be performed to rule out other conditions. Phototesting can also be used to confirm the diagnosis by reproducing the rash with controlled UV exposure.

Management

Management of PMLE involves both preventive and therapeutic measures. Preventive strategies include:

• Avoiding sun exposure, especially during peak hours.
• Wearing protective clothing and wide-brimmed hats.
• Using broad-spectrum sunscreen with high SPF.

Therapeutic options for managing symptoms include:

• Topical corticosteroids to reduce inflammation.
• Oral antihistamines to alleviate itching.
• In severe cases, phototherapy or immunosuppressive agents may be considered.

Prognosis

The prognosis for PMLE is generally good, with most individuals experiencing improvement with preventive measures and treatment. However, the condition can be recurrent, particularly during the spring and summer months when sun exposure is more frequent.

Epidemiology

PMLE is more common in women than men and typically occurs in young adults. It is also more prevalent in individuals with fair skin types. The condition is less common in tropical regions, possibly due to the development of natural photoprotection from chronic sun exposure.

See also

• Photodermatosis
• Sunscreen
• Ultraviolet radiation
• Skin biopsy
• Phototherapy