What are the treatment options for a patient with Polymorphic Light Eruption (PMLE)?

Treatment of Polymorphic Light Eruption (PMLE)

All patients with PMLE should begin with strict photoprotection using broad-spectrum sunscreens (SPF ≥15 with high UVA protection) combined with potent topical corticosteroids applied to active lesions, escalating to prophylactic phototherapy (narrowband UVB preferred over PUVA) for moderate-to-severe disease that impairs quality of life despite optimal sun protection. 1, 2

First-Line Management: Photoprotection and Topical Corticosteroids

Photoprotection Strategy

• Apply broad-spectrum sunscreens with high UVA protection potential (SPF ≥15) daily to all sun-exposed areas 1, 3
• Avoid sun exposure during peak UV hours (10 AM to 4 PM) and actively seek shade 1
• Use UV-protective clothing as the most effective physical barrier, though not always practical for all exposed areas 3
• Research demonstrates that sunscreens combining potent UVA filters (methylene bis-benzotriazolyl tetramethylbutylphenol, bis-ethylhexyloxyphenol methoxyphenyl triazine) successfully prevent PLE development under standardized conditions 3

Topical Corticosteroid Selection by Anatomic Site

• For facial involvement: Apply hydrocortisone 1% once to twice daily due to increased risk of atrophy, telangiectasias, and rosacea-like eruptions with higher potency agents 2
• For trunk and extremities: Apply potent topical corticosteroids (betamethasone or hydrocortisone butyrate) immediately after UV exposure or at first sign of eruption 1, 2, 4
• Timing is critical: Prophylactic application immediately after UV exposure reduces provocation rates more effectively than delayed application 2

Acute Severe Flares

• Oral prednisolone 40-50 mg may be used for severe acute flares that are widespread or refractory to topical therapy 1, 5

Second-Line Management: Prophylactic Phototherapy

Indications for Phototherapy

• Moderate-to-severe PLE causing substantial quality of life impairment despite optimal photoprotection 1, 5
• Patients requiring reliable photoprotection for occupational or lifestyle reasons 5

Narrowband UVB (Preferred Modality)

• Narrowband UVB should be the first-line phototherapy choice due to comparable efficacy to PUVA (88-89% of patients report good or moderate improvement) with lower long-term skin cancer risk 1
• Administer in early spring to maintain photoprotection through mid-summer 1
• Treatment frequency typically twice weekly for 12-20 sessions 1

PUVA Therapy (Alternative When NB-UVB Insufficient)

• PUVA administered twice weekly in early spring for 12-20 treatments using UK standard protocols 1
• Critical timing: Must begin in early spring to achieve photoprotection through mid-summer 1
• PUVA carries higher long-term carcinogenesis risk; patients receiving >150-200 exposures require annual skin cancer surveillance 6, 1
• PUVA should be avoided during pregnancy as it is mutagenic, though not proven to be a significant teratogen 6

Managing Phototherapy Provocation Risk

The risk of provoking PLE during phototherapy is substantial (12-50% with PUVA, 48-62% with UVB), particularly during initial exposures 1. Implement these prophylactic measures:

• Oral prednisolone 40-50 mg for the first 2 weeks of phototherapy 1
• Routine prophylactic application of potent topical corticosteroid immediately after each exposure for the first 6 treatments 1, 2
• If provocation occurs: apply potent topical steroids, reduce subsequent dose increments, and omit 1-2 treatments if particularly severe 2

Post-Phototherapy Maintenance

• Continued natural sunlight exposure is essential post-treatment to maintain photoprotection through summer 1
• Annual desensitization courses are generally not recommended due to cumulative skin carcinogenesis risk 1

Adjuvant Preventive Approaches

Topical Antioxidants

• Formulations combining 0.25% alpha-glucosylrutin, 1% tocopheryl acetate (vitamin E), and broad-spectrum UVA-protective sunscreen demonstrate statistically significant superiority over sunscreen alone (P<0.001), with only 3.4% developing PLE versus 62.1% with placebo 7
• This represents an effective and well-tolerated option for moderate-to-severe PLE 5

Alternative Phototherapy Modalities

• UVA1 irradiation may be considered when narrowband UVB is ineffective 5
• PUVA bath therapy reserved for cases where both narrowband UVB and UVA1 fail, used with caution due to acute and long-term adverse effects 5

Therapy-Resistant Cases

For severe, refractory PLE unresponsive to standard measures:

• Systemic immunosuppressive drugs may rarely be required 5, 8
• Afamelanotide (induces skin melanization) represents a potential new treatment option for very severe and refractory cases 8
• IL-31 targeting therapies are emerging for cases with intense pruritus 8

Common Pitfalls to Avoid

• Inadequate UVA protection: Most conventional sunscreens protect predominantly against UVB and fail to prevent PLE, which is mainly provoked by UVA (320-400 nm) 3
• Wrong timing of phototherapy: Starting phototherapy too late in the season (after spring) fails to provide adequate photoprotection during peak summer months 1
• Inappropriate corticosteroid potency for facial lesions: Using potent steroids on the face increases risk of atrophy and telangiectasias 2
• Failure to implement provocation prophylaxis: Not using oral prednisolone and topical corticosteroids during initial phototherapy exposures leads to high provocation rates that may discourage patients from continuing treatment 1, 2