polymorphous light eruption (PMLE)

Introduction

A group of heterogenous, idiopathic, acquired, acute & recurrent photodermatoses characterized by delayed skin reactions to UV radiation.

Etiology

• precipitated most frequently by exposure to UV-A, but also UV-B or by both
• since UV-A is transmitted through glass, PMLE may be preciptated while driving or riding in a motor vehicle
• appears to be a threshold for elicitation of PMLE
• may be delayed hypersensitivity reaction to antigen induced by UV radiation

Epidemiology

• average age of onset is 23 years
• most common of the photodermatoses
• all races
• much more common in females
• less frequently observed in sunbelt (year-round sun)
• often occurs for 1st time in individuals traveling for short vacations to the tropics in winter from northern latitudes
• occurs in spring & early summer in temperate zones

Pathology

• edema of the epidermis
• basal layer with spongiosis, vesicle formation & mild liquefaction degeneration
• no thickening or atrophy of the basement membrane
• dense lymphocytic (T-cell) infiltrate in the dermis
• occasional neutrophils in the dermis
• edema of the papillary dermis
• endothelial swelling
• direct immunofluorescence for IgG is negative

Clinical manifestations

• monomorphous reaction consisting of macules, papules, plaques or vesicles (papular & papulovesicular eruptions are most common)
• lesions are pink to red
• rash occurs suddenly after hours to days of sun exposure
• most frequently appears within 18-24 hours of exposure
• persists for 7-10 days (may persist for weeks)
• areas of skin habitually exposed (face & neck) may be spared despite severe involvement of trunk & extremities
• pruritus & paresthesia may precede the rash
• lesions resolve without scarring
• chronic & recurrent disorder, may become worse each season
• patients may develop a tolerance by the end of summer, but generally recurs the following season
• spontaneous improvement or resolution generally occurs after several years

Laboratory

• serology: anti-nuclear antibody (ANA) 3-19%
• complete blood count (CBC): no leukopenia
• biopsy (if plaque-type lesions)
• phototesting with UV-A & UV-B

Complications

• ANA+ PMLE does NOT transform to lupus

Differential diagnosis

• lupus erythematosus (plaque-type lesions)
• drug reaction
• allergic reaction to cosmetic

Management

• sunscreens
  • rarely effective, but should be tried 1st
  • should be used in conjunction with systemic medication or PUVA
• beta carotene not very effective, but may be tried
• hydroxychloroquine 200 mg PO BID
  • one day before & daily while vacationing or on weekends in the sun
  • effective in some patients
  • use in patients not helped by sunscreens or beta-carotene
• PUVA photochemotherapy
  • given in early spring induces tolerance for the following summer
  • treatments 3 times weekly for 4 weeks
  • repeat each spring for 3-4 years

More general terms

• photosensitivity

More specific terms

• actinic prurigo; hydroa estivale; Hutchinson's summer prurigo

Additional terms

• UV-A radiation
• UV-B radiation