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Skin-nontumor / Clinical Dermatology

Other dermatoses

Polymorphous light eruption

Reviewer: Mowafak Hamodat, MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns, Canada (see Reviewers page)
Revised: 1 August 2011, last major update August 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● The most common photodermatosis
● Presents in young adults as recurrent erythematosus papules, vesicles or plaques on face, chest, upper back and extremities
● Onset of lesions 18-24 hours after light exposure, usually in spring/summer
● Associated with thyroid disease or lupus in some patients
● Juvenile spring eruption appears to be either a form of polymorphous light eruption or a closely related disorder
● Use photo testing to establish diagnosis

Clinical images

Polymorphic light eruption on arm

Micro description

● Perivascular lymphohistiocytic infiltrate in superficial and sometimes deep dermis
● Papillary dermal edema; epidermal acanthosis, spongiosis, occasional dyskeratotic cells and lymphocytic exocytosis
● Basal cell vacuolation is mild
● Periadnexal involvement may be seen; variable increase in eosinophils and neutrophils

Micro images

Polymorphous light eruption

Positive stains

● Direct immunofluorescence shows C3, IgM and IgG at basal layer of dermoepidermal junction

Differential diagnosis

● Reticulae erythematous mucinosis: has dermal mucin, not present in polymorphic light eruption
● Gyrate erythema such as lymphocytic infiltration of Jessner
● Actinic reticuloid: dense cellular and interstitial infiltrate of papillary and reticular dermis that may extend to subcutaneous fat; composed of variable lymphocytes, histiocytes, eosinophils and plasma cells; multinucleated giant cells are conspicuous; also large atypical hyperchromatic cerebriform lymphoid cells and blast forms

Additional references


End of Skin-nontumor / Clinical Dermatology > Other dermatoses > Polymorphous light eruption

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