A 40-year-old woman presents for evaluation of a rash first noted approximately 1 week ago. She complains of minimal itchiness and no pain. According to the patient, a similar rash has occurred on a yearly basis. The prior eruptions began early to mid-spring and resolved without treatment after approximately 2 weeks. She denies fever, joint pains, swollen glands, and history of fever blisters. She is in good health and is not taking any oral medications. Examination reveals multiple erythematous slightly indurated papules and patches. Her palms and soles are unaffected.
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Polymorphous light eruption (PMLE) is the most common form of photodermatosis.1 The condition is most common in White women aged 20 to 40 years and is infrequently diagnosed in Black, Indigenous, and people of color.1 The rash typically appears in spring or early summer and is believed to result from a delayed-type hypersensitivity reaction triggered by ultraviolet radiation.2
Skin lesions usually present within hours of sun exposure and can persist for 7 to 10 days. Classic presentation is the appearance of erythematous papules and papulovesicles that arise in stages. Accompanying symptoms may include pruritus and a burning sensation. The skin lesions typically resolve without scarring and recurrent lesions tend to follow the original pattern. The most common areas of involvement are the forearms, V area of the neck, and chest.3
Diagnosis of PMLE is often made by history. Patients will complain of a rash that occurs each year following initial exposure to sunlight. When the presentation is atypical, biopsy and immunofluorescence studies are prudent to rule out lupus erythematosus.4 Biopsy findings of PMLE show edema in the dermis and perivascular infiltration with negative immunofluorescence.
Protection from the sun with sunscreen and protective clothing is encouraged for patients with a history of PMLE.5 Steroids, both oral and intramuscular, and narrowband UV light phototherapy (twice weekly for 1 month) may suppress the rash when administered prior to sun exposure.6,7
Sara Mahmood, DPN, is a podiatrist who completed a joint dermatology/podiatry fellowship and is on staff at DermDox Dermatology Centers. Stephen Schleicher, MD, is director of the DermDox Dermatology Centers in Pennsylvania, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
1. Oakley AM, Ramsey ML. Polymorphic light eruption. In: StatPearls. StatPearls Publishing; August 11, 2021.
2. Gruber-Wackernagel A, Byrne SN, Wolf P. Polymorphous light eruption: clinic aspects and pathogenesis. Dermatol Clin. 2014;32(3):315-viii. doi:10.1016/j.det.2014.03.012
3. O’Gorman SM, Murphy GM. Photoaggravated disorders. Dermatol Clin. 2014;32(3):385-ix. doi:10.1016/j.det.2014.03.008
4. Van Praag MC, Boom BW, Vermeer BJ. Diagnosis and treatment of polymorphous light eruption. Int J Dermatol. 1994;33(4):233-239. doi:10.1111/j.1365-4362.1994.tb01033.x
5. Lembo S, Raimondo A. Polymorphic light eruption: what’s new in pathogenesis and management. Front Med (Lausanne). 2018;5:252. doi:10.3389/fmed.2018.00252
6. Ling TC, Gibbs NK, Rhodes LE. Treatment of polymorphic light eruption. Photodermatol Photoimmunol Photomed. 2003;19(5):217-227. doi:10.1034/j.1600-0781.2003.00048.x
7. Combalia A, Fernández-Sartorio C, Fustà X, Morgado-Carrasco D, Podlipnik S, Aguilera P. Successful short desensitization treatment protocol with narrowband UVB phototherapy (TL-01) in polymorphic light eruption. Actas Dermosifiliogr. 2017;108(8):752-757. doi:10.1016/j.ad.2017.04.004