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polymorphous light eruption (PMLE)
A group of heterogenous, idiopathic, acquired, acute & recurrent photodermatoses characterized by delayed skin reactions to UV radiation.
Etiology:
1) precipitated most frequently by exposure to UV-A, but also UV-B or by both
2) since UV-A is transmitted through glass, PMLE may be preciptated while driving or riding in a motor vehicle
3) appears to be a threshold for elicitation of PMLE
4) may be delayed hypersensitivity reaction to antigen induced by UV radiation
Epidemiology:
1) average age of onset is 23 years
2) most common of the photodermatoses
3) all races
4) much more common in females
5) less frequently observed in sunbelt (year-round sun)
6) often occurs for 1st time in individuals traveling for short vacations to the tropics in winter from northern latitudes
7) occurs in spring & early summer in temperate zones
Pathology:
1) edema of the epidermis
2) basal layer with spongiosis, vesicle formation & mild liquefaction degeneration
3) no thickening or atrophy of the basement membrane
4) dense lymphocytic (T-cell) infiltrate in the dermis
5) occasional neutrophils in the dermis
6) edema of the papillary dermis
7) endothelial swelling
8) direct immunofluorescence for IgG is negative
Clinical manifestations:
1) monomorphous reaction consisting of macules, papules, plaques or vesicles (papular & papulovesicular eruptions are most common)
2) lesions are pink to red
3) rash occurs suddenly after hours to days of sun exposure
4) most frequently appears within 18-24 hours of exposure
5) persists for 7-10 days (may persist for weeks [3])
6) areas of skin habitually exposed (face & neck) may be spared despite severe involvement of trunk & extremities
7) pruritus & paresthesia may precede the rash
8) lesions resolve without scarring [3]
9) chronic & recurrent disorder, may become worse each season
10) patients may develop a tolerance by the end of summer, but generally recurs the following season
11) spontaneous improvement or resolution generally occurs after several years
Laboratory:
1) serology: anti-nuclear antibody (ANA) 3-19% [2]
2) complete blood count (CBC): no leukopenia
3) biopsy (if plaque-type lesions)
4) phototesting with UV-A & UV-B
Differential diagnosis:
1) lupus erythematosus (plaque-type lesions)
2) drug reaction
3) allergic reaction to cosmetic
Complications:
- ANA+ PMLE does NOT transform to lupus [2]
Management:
1) sunscreens
a) rarely effective, but should be tried 1st
b) should be used in conjunction with systemic medication or PUVA
2) beta carotene not very effective, but may be tried
3) hydroxychloroquine 200 mg PO BID
a) one day before & daily while vacationing or on weekends in the sun
b) effective in some patients
c) use in patients not helped by sunscreens or beta-carotene
4) PUVA photochemotherapy
a) given in early spring induces tolerance for the following summer
b) treatments 3 times weekly for 4 weeks
c) repeat each spring for 3-4 years
Related
UV-A radiation
UV-B radiation
Specific
actinic prurigo; hydroa estivale; Hutchinson's summer prurigo
General
photosensitivity
References
- Color Atlas & Synopsis of Clinical Dermatology, Common
& Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY,
1997, pg 250-53
- Tzaneva S et al
Antinuclear antibodies in patients with polymorphic light
eruption: a long-term follow-up study.
Br J Dermatol. 2008 May;158(5):1050-4. Epub 2008 Mar 13.
PMID: 18341657
- Medical Knowledge Self Assessment Program (MKSAP) 19
American College of Physicians, Philadelphia 2022