Polymorphic light eruption
Related Subjects:
|Nikolsky's sign
|Koebner phenomenon
|Erythema Multiforme
|Pyoderma gangrenosum
|Erythema Nodosum
|Dermatitis Herpetiformis
|Lichen Planus
|Acanthosis Nigricans
|Acne Rosacea
|Acne Vulgaris
|Alopecia
|Vitiligo
|Urticaria
|Basal Cell Carcinoma
|Malignant Melanoma
|Squamous Cell Carcinoma
|Mycosis Fungoides (Sezary Syndrome)
|Xeroderma pigmentosum
|Bullous Pemphigoid
|Pemphigus Vulgaris
|Seborrheic Dermatitis
|Pityriasis/Tinea versicolor infections
|Pityriasis rosea
|Scabies
|Dermatomyositis
|Toxic Epidermal Necrolysis
|Stevens-Johnson Syndrome
|Atopic Eczema/Atopic Dermatitis
|Psoriasis
📖 About
- Polymorphic Light Eruption (PLE) is the most common photosensitivity disorder, especially in young women (peak 20–40 years).
- It represents a delayed hypersensitivity reaction to an UV-induced endogenous antigen in the skin.
- Triggered mainly by UVA (long-wave) radiation, but UVB can also provoke lesions.
- Unlike lupus-related photosensitivity, PLE is benign with no systemic disease association.
👀 Clinical Features
- Seasonal pattern: flares in spring/early summer, improves (“hardening phenomenon”) as tolerance develops through the season.
- Affects sun-exposed sites – face, V of neck, arms, and upper chest; sparing areas shaded by clothing/jewellery.
- Rash morphology is variable (“polymorphic”):
- Papular – most common
- Vesicular – blisters
- Plaque-like or erythematous patches
- Distribution is typically symmetrical.
- Lesions appear within hours–days after UV exposure, often itchy or burning, and resolve without scarring.
🔍 Differentials
- Cutaneous lupus erythematosus – photosensitivity with systemic features/autoantibodies.
- Solar urticaria – immediate whealing within minutes of exposure (vs delayed in PLE).
- Porphyria cutanea tarda – blistering, scarring on sun-exposed sites, often with liver disease.
💊 Management
- Prevention:
- High-factor, broad-spectrum sunscreen (UVA + UVB)
- Avoid midday sun, wear protective clothing, wide-brimmed hats 🧢
- Desensitisation:
- Phototherapy (UVB or PUVA) started in early spring can induce tolerance before summer.
- Symptomatic relief:
- Topical corticosteroids for inflamed lesions
- Oral antihistamines for itch
- Generally benign, seasonal recurrence is common, but there are no long-term sequelae.
✅ Exam Pearls
- Most common photosensitivity disorder.
- Triggered mainly by UVA (vs sunburn = UVB).
- Seasonal recurrence, improves with ongoing exposure (“hardening”).
- Differentials: lupus, solar urticaria, porphyria cutanea tarda.
