A 37-year-old Caucasian man presents with a red and itchy rash he’s had for the past 7 days. He recently returned from a week-long vacation on the Florida coastline. He noticed his symptoms 3 days after arrival. He had a milder episode 1 year ago, and the rash eventually cleared. He denies having contact with any plants, insects, or wildlife. He says that his symptoms started to improve after returning home from the beach. He denies any personal or family history of skin disease and stated he is not taking any medications. He confirmed that he uses SPF 15 sunscreen.
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The diagnosis is PMLE, which is characterized as a delayed abnormal reaction to UV radiation causing erythemic lesions, including macules, papules, plaques, and/or vesicles. Although most cases present as pleomorphic or polymorphic, some patients may experience monophoric lesions. Any sun-exposed area that is generally covered throughout the year is at risk for eruption. Contact dermatitis can be ruled out as the patient did not have any new contact with irritants, and the symmetrical and equal distribution pattern on both calves would make it highly unlikely. The patient did not report any pain, and the areas of concern were bilateral, ruling out herpes zoster. Finally, a localized allergic reaction is plausible; however, the patient denies being bitten or stung by any insects and was confined to his condo rental and beachfront the entire time. The emergency department PA correctly diagnosed the patient with PMLE and prescribed topical steroids and educated the patient to avoid prolonged exposure to the sun and apply a higher level of sunblock. The patient followed up with his primary care provider in 2 days, at which time the eruption had cleared.1,2
PLME is a common photosensitivity disorder more common in white Caucasians with a prevalence of 11% to 21% in the Northern Hemisphere population. Overall, the disease is more prevalent in temperate climates and typically occurs as a polymorphic or pleomorphic pruritic eruption that occurs in sun-exposed areas that have been covered by clothes throughout the year. The lesions most commonly present as papules, vesicles, and/or plaques. Eruption begins within hours to days after initial sun exposure. The initial eruption usually occurs in the spring, with severe cases resolving in the fall. The disease follows a spectrum of mild to severe disease. The single most important aspect is prevention, which entails sun avoidance and appropriate sunblock. Mild cases will generally resolve on their own, and patients can achieve symptom improvement quicker with topical steroids; however, severe and persistent cases may require systemic steroids, phototherapy, and/or photochemotherapy. Although the pathogenesis is not fully understood, it is widely believed that the disease is caused by a delayed-type hypersensitivity immunologic reaction and likely has a strong hereditary component.3 A detailed personal history is extremely important for this disease as it can closely mimic contact dermatitis.
David A. Smith, PA-C, is a full-time professor in the PA Program at Salus University and practices emergency and critical care medicine at Suburban Community Hospital and the Philadelphia VA Medical Center.
- Epstein JH. Polymorphous light eruption. Photodermatol Photoimmunol Photomed. 1997;13:89-90.
- Wolff K, Johnson R, Saavedra AP. Photosensitivity, photo-induced disorders, and disorders by ionizing radiation. In: Wolff K, Johnson R, Saavedra AP, eds. Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology. 7th ed. New York, NY: McGraw-Hill; 2013.
- Ling TC, Gibbs NK, Rhodes LE. Treatment of polymorphic light eruption. Photodermatol Photoimmunol Photomed. 2003;19:217-227.