Skin inflammatory (nontumor)
Dermal perivascular and vasculopathic reaction patterns
Polymorphous light eruption

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 15 October 2018, last major update August 2011

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Polymorphous light eruption

Cite this page: Hamodat, M. Polymorphous light eruption. website. Accessed October 22nd, 2018.
Definition / general
  • 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

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Polymorphic light eruption on arm

Microscopic (histologic) 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
Microscopic (histologic) images

Images hosted on other servers:

Polymorphous light eruption

Positive stains
  • Direct immunofluorescence shows C3, IgM and IgG at basal layer of dermoepidermal junction
Differential diagnosis
  • 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
  • Gyrate erythema such as lymphocytic infiltration of Jessner
  • Reticulae erythematous mucinosis: has dermal mucin, not present in polymorphic light eruption
  • SLE
Additional references