Polymorphous Light Eruption (PMLE): Symptoms, Causes, Treatment

What are the symptoms of polymorphous light eruption?

Polymorphous light eruption (PMLE) is a skin condition triggered by exposure to sunlight or artificial UV light. The symptoms typically appear within hours to a few days after exposure and can vary in presentation. Common symptoms include:

Redness and Rash: A red, itchy rash often appears on sun-exposed areas of the skin, such as the face, neck, arms, and chest.
Itchy or Burning Sensation: Affected areas may feel itchy or have a burning sensation.
Small Bumps or Blisters: The rash may consist of small red bumps, raised patches, or fluid-filled blisters.
Plaques: Some people may develop raised, red patches or plaques.
Swelling: The affected skin may become swollen.
Timing: Symptoms generally appear after sun exposure and may persist for a few days to a week or more, then resolve without scarring.
Location: PMLE typically affects areas that are usually covered during the winter months and then exposed to the sun in the spring and summer, such as the upper chest, arms, and legs. The face and the back of the hands are less commonly affected.

The intensity of symptoms can vary from mild to severe, and while PMLE is generally not dangerous, it can cause significant discomfort and impact daily life, especially during sunny seasons.

What are the causes of polymorphous light eruption?

Polymorphous light eruption (PMLE) is a skin condition triggered by exposure to sunlight or artificial ultraviolet (UV) radiation. The exact cause is not fully understood, but several factors contribute to its development:

Abnormal immune reaction to UV light: PMLE is thought to occur when the immune system reacts abnormally to sunlight (specifically UVA and UVB rays). It sees the UV-exposed skin as foreign, triggering an inflammatory response.
Genetic predisposition: People with a family history of PMLE may be more susceptible to developing the condition. It is more common in women and people of European descent.
Seasonal factors: PMLE often occurs after the first significant sun exposure of the season (spring or early summer), when the skin is not yet adapted to UV light.
Environmental triggers: High altitudes and locations with intense sunlight can increase the likelihood of PMLE in those predisposed to the condition.
Photosensitizing substances: Certain medications, creams, or chemicals can increase sensitivity to light, leading to a higher chance of PMLE.

Once triggered, PMLE typically presents as a rash with itchy or burning red bumps, plaques, or blisters on sun-exposed areas of the skin.

How is the diagnosis of polymorphous light eruption made?

The diagnosis of polymorphous light eruption (PMLE) is primarily clinical, based on the patient’s history and the characteristic appearance of the rash. The diagnostic process generally involves:

1. Clinical History

Sun Exposure: The patient’s history of sun exposure and the timing of rash onset are crucial. PMLE symptoms typically develop within hours to days after exposure to sunlight or UV light.
Pattern of Rash: The rash usually appears on areas that were exposed to the sun and resolves within a few days of avoiding further sun exposure.
Recurrence: Information about recurring episodes each year, often coinciding with increased sun exposure, helps in diagnosis.

2. Physical Examination

Appearance of Rash: The rash’s characteristic features, such as red, itchy bumps, plaques, or blisters, especially on sun-exposed areas (face, neck, arms, and chest), are assessed.
Distribution: The rash is often confined to areas exposed to sunlight, with less involvement of covered areas.

3. Diagnostic Tests

Phototesting: A controlled exposure to UV light in a clinical setting can help confirm the diagnosis. Phototesting involves exposing small areas of the skin to UV light and observing for a reaction.
Skin Biopsy: In some cases, a skin biopsy may be performed to rule out other conditions. The biopsy might show superficial perivascular lymphocytic infiltrate and other features consistent with PMLE.

4. Differential Diagnosis

Ruling Out Other Conditions: It is important to differentiate PMLE from other sun-induced skin conditions, such as solar urticaria, lupus erythematosus, and other types of photosensitivity disorders.

The diagnosis is usually made based on a combination of clinical evaluation and the response to phototesting. Consulting a dermatologist is often necessary for an accurate diagnosis and management plan.

What is the treatment for polymorphous light eruption?

The treatment for polymorphous light eruption (PMLE) focuses on managing symptoms and preventing future outbreaks. The approach typically includes:

1. Sun Protection

Avoid Sun Exposure: Minimize time in the sun, especially during peak hours.
Use Sunscreen: Apply broad-spectrum sunscreen with a high SPF (30 or higher) regularly, even on cloudy days.
Protective Clothing: Wear sun-protective clothing, such as long sleeves, hats, and sunglasses, when outdoors.

2. Medications

Topical Corticosteroids: Apply corticosteroid creams or ointments to reduce inflammation and itching during flare-ups.
Oral Antihistamines: Use antihistamines to alleviate itching and discomfort.
Oral Corticosteroids: In severe cases, short courses of oral corticosteroids may be prescribed for more significant flare-ups.

3. Phototherapy

Gradual UV Exposure: Controlled exposure to UV light (phototherapy) under medical supervision can help desensitize the skin and reduce the likelihood of future flare-ups. This treatment is often used in chronic or severe cases.

4. Prevention Strategies

Gradual Sun Exposure: Gradually increase sun exposure over time to build up tolerance. This should be done cautiously to avoid severe reactions.
Sunlamps: In some cases, UV light exposure from sunlamps may be used to help build tolerance, similar to phototherapy.

5. Lifestyle Modifications

Maintain a Healthy Skin Routine: Keeping the skin well-moisturized can help reduce irritation and improve skin resilience.
Monitor Sun Exposure: Keep track of sun exposure and symptoms to better manage and avoid triggers.

6. Consult a Dermatologist

Specialized Advice: Regular follow-ups with a dermatologist can help tailor the treatment plan to individual needs and adjust strategies as necessary.

The effectiveness of treatment can vary from person to person, and managing PMLE often requires a combination of approaches to prevent and control symptoms effectively.