Polymorphous
Light Eruption (PMLE)
Epidemiology and Etiology:
- Idiopathic
- Occurs hours to
days after sun exposure
- Subsides in 7-10d
after avoiding exposure
- Genetic influence
- 10-20% of those
living in temperate climates
- much less common in
populations near the equator
Common sites:
- dorsum of
hands and forearms
- upper arms
- neck
- face
Gross features:
- various
morphology
- small pruritic
papules
- papulovesicles
- urticarial plaques
Histologic features:
- marked variability
- superficial and
deep dermal inflammatory infiltrate is fairly consistent feature
- edema of upper
dermis often
- basal vacuolation
often
- no cell death or
basement membrane thickening
- may see:
- heavy superficial
infiltrate of lymphocytes in upper dermis
- eosinophils
- neutrophils
- subepidermal
bullae
- extravasation of
RBCs
- spongiosis
- focal
parakeratosis
- focal acanthosis
- exocytosis of
lymphocytes and erythrocytes
- no interface
dermatitis
- no dermal deposits
of acid mucopolysaccharides (as seen in lupus)
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- chronic
condition
- may develop
eventual tolerance to sunlight
References: