Polymorphic Light Eruption (PLE) is the Most Likely Diagnosis
This 44-year-old woman most likely has polymorphic light eruption (PLE), and initial management should include strict photoprotection with high SPF broad-spectrum sunscreen and potent topical corticosteroids for symptomatic relief.
Clinical Reasoning
The presentation is classic for PLE:
- Raised, non-pruritic patch on sun-exposed area (left upper cheek)
- Acute onset (5 days ago, "woke up with it")
- Photosensitivity (worsens with sun exposure)
- Age and demographics (middle-aged woman, common demographic for PLE)
- No prior history suggesting this is a new photodermatosis
The absence of itching is somewhat atypical for PLE (which usually causes pruritus), but the temporal relationship to sun exposure and the raised patch-like morphology on the face strongly support this diagnosis 1.
Key Differential Diagnoses to Consider
While PLE is most likely, briefly evaluate for:
- Solar urticaria: Would present within minutes of sun exposure with urticarial wheals that resolve within hours, not days 2, 3
- Chronic actinic dermatitis (CAD): Presents as chronic dermatitis on sun-exposed skin, not acute onset 1
- Cutaneous lupus erythematosus: Can present with facial erythema worsening with sun, but typically has more persistent lesions and may show systemic features 4
- Photocontact dermatitis: Requires exposure to photosensitizing agent plus sunlight 5
Immediate Management Approach
First-Line Treatment:
Strict photoprotection:
- High SPF (≥30) broad-spectrum sunscreen covering UVA and UVB 1
- Reapply every 2-3 hours during sun exposure
- Protective clothing, wide-brimmed hat
- Avoid sun exposure during peak hours (10 AM - 4 PM)
Potent topical corticosteroid:
- Apply to affected area twice daily 1
- This manages the current eruption and can prevent provocation if lesions recur
If Initial Treatment Fails:
If lesions persist or recur despite photoprotection, consider:
- Prophylactic phototherapy (PUVA or narrowband UVB) administered in early spring for desensitization 1
- Start with low doses as PLE has high risk of provocation with phototherapy (12-50% of treatment courses) 1
- Cover with potent topical steroid or short-term oral prednisolone (40-50 mg for first 2 weeks) to prevent provocation 1
Important Clinical Caveats
Common pitfall: Do not apply sunscreen immediately before attempting phototherapy, as this creates areas of differential tolerance that may burn on subsequent exposures 6.
Timing consideration: If phototherapy is chosen, administer in early spring. Too early and protection wanes by mid-summer; too late and the patient may have already suffered eruptions 1.
Long-term perspective: PLE is a chronic relapsing condition. Individual lesions may spontaneously regress, but the patient will likely develop new lesions with future sun exposure. Continued photoprotection is essential 1.
The raised, non-itchy nature and 5-day duration make this less likely to be solar urticaria (which resolves within hours) or chronic actinic dermatitis (which would show chronic changes). Start with aggressive photoprotection and topical corticosteroids, and reassess in 2-3 weeks.