Polymorphous Light Eruption

Aka: Polymorphous Light Eruption, Polymorphic photodermatitis, Polymorphic Light Eruption, Actinic Prurigo, PMLE

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II. Epidemiology

  1. Most common Photodermatitis
    1. Prevalence may be as high as 10-20% in adults (esp. in Fitzpatrick Skin Type 1-3)
  2. Gender: Female predominance
  3. Age onset 23 years

III. Pathophysiology

  1. Primarily triggered by UVA exposure
  2. May be a Type 4 Hypersensitivity (Delayed-Type Hypersensitivity) reaction

IV. Types

  1. Papular (most common)
  2. Papulovesicular (common)
  3. Actinic Prurigo (Hutchinson Summer Eruption)
    1. Hereditary form of Polymorphous Light Eruption seen in Native Americans

V. Symptoms

  1. Onset
    1. Intensely pruritic rash within hours of Sun Exposure
    2. Rash is painful when scratched
  2. Timing
    1. Most common after Sun Exposure (even through car windows) in spring and early summer
    2. Persists 7 to 10 days

VI. Findings

  1. Pink to red lesions
    1. Primarily papular or papulovesicular
    2. Rarely Plaques or Urticaria
  2. Distribution
    1. Lesions may affect face (but typically spares other areas of the head and neck)
    2. Most commonly affected regions
      1. V-Neck region
      2. Forearms and upper arms
      3. Chest

VII. Differential Diagnosis

  1. See Photodermatitis

VIII. Course

  1. Chronic and recurrent after Sun Exposure by early summer
  2. Reactions become less significant with tolerance by late summer (only to recur in the following year)
  3. May spontaneously resolve over the course of years

IX. Management

  1. Sunscreen
    1. First-line measure, but not uniformly effective
    2. Apply SPF 50 Sunscreens every 2 hours to exposed skin
  2. Prophylaxis
    1. Beta Carotene
      1. Take 60 mg orally three times daily for 2 weeks before Sun Exposure
    2. PUVA and Narrow Band UVB at 311 nm
      1. Given in early spring (before sunny season) to induce tolerance
      2. Annual treatment with 2-3 sessions per week for 4 to 6 weeks (for 3-4 years)
    3. Corticosteroids
      1. Prednisone 20 mg/day starting 2 days before and continuing for 2 days after start of Sun Exposure OR
      2. Triamcinolone Acetonide 40 mg IM given 2 days prior to travel to sunny region

X. References

  1. Wolff et. al. (2017) Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology, McGraw-Hill, Chicago, p. 202-3
  2. Oakley (2023) Polymorphic Light Eruption, StatPearls, Treasure Island
    1. https://www.ncbi.nlm.nih.gov/books/NBK430886/

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