Methotrexate for Severe Polymorphic Light Eruption
Methotrexate is not a recognized treatment for severe polymorphic light eruption (PLE) and should not be used for this indication.
Evidence-Based Treatment Hierarchy for Severe PLE
First-Line: Photoprotection
- Apply broad-spectrum sunscreens with SPF ≥30 and high UVA protection daily, avoiding sun exposure during peak hours (10 AM to 4 PM) 1, 2.
- Use potent topical corticosteroids (betamethasone or hydrocortisone butyrate) on the trunk and low-potency hydrocortisone 1% on the face for active lesions 3, 2.
- For severe acute flares, oral prednisolone 40-50 mg may be administered 1, 2.
Second-Line: Prophylactic Phototherapy (The Definitive Treatment for Severe PLE)
Narrowband UVB is the preferred phototherapy modality for severe PLE, particularly in younger patients, due to equivalent efficacy to PUVA (88-89% reporting good or moderate improvement) but with lower long-term skin cancer risk 1, 2.
Treatment Protocol:
- Administer twice weekly in early spring for 12-20 treatments to achieve photoprotection through mid-summer 1, 2.
- Start at 70% of minimal erythema dose with 20% increments to minimize provocation risk 1.
- Apply potent topical corticosteroids immediately after each phototherapy session for the first 6 exposures to prevent provocation of PLE during treatment 3.
- Consider prophylactic oral prednisolone (40-50 mg) for the first 2 weeks of phototherapy, as provocation risk is high (48-62% with narrowband UVB) 1.
PUVA as Alternative:
- PUVA may be used if narrowband UVB fails, administered twice weekly for 12-20 treatments 1, 2.
- PUVA has lower provocation rates (12-50%) compared to narrowband UVB but carries higher long-term skin cancer risk 1.
Critical Monitoring Requirements:
- Patients receiving >150-200 PUVA exposures require annual skin cancer surveillance 1, 2.
- Annual desensitization is generally not recommended due to cumulative carcinogenesis risk 1, 2.
- Continued natural sunlight exposure post-treatment is essential to maintain photoprotection through summer 1, 2.
Why Methotrexate Is Not Used
The medical literature on PLE management does not include methotrexate as a treatment option 4, 5, 6. While methotrexate has been studied as an immunomodulatory agent in pemphigus vulgaris (showing clinical improvement in 83% of patients at doses of 10-50 mg per week), this was in combination with corticosteroids for an entirely different autoimmune blistering disease 7. PLE is a delayed hypersensitivity photodermatosis, not a systemic autoimmune disease requiring systemic immunosuppression 5.
The established treatment paradigm for severe PLE focuses on photohardening through controlled UV exposure, not systemic immunosuppression 4, 5, 6, 8. Quality of life improvement in most severe PLE patients is achieved with phototherapy protocols without requiring systemic immunosuppressive agents 4.