A 13-year-old girl who lived in Canada went on a winter vacation in Hawaii. After a day at the beach, she was awakened on the second day by this intensely itchy, blistering reaction on her forearms and upper chest. The rash persisted for a week despite sun avoidance. No other parts of her body were involved, even though other areas had been exposed to the sun.
She had polymorphic light eruption (PMLE), the most common abnormal reaction to UV light, which classically presents as a papular or papulovesicular eruption on the arms and anterior chest with sparing of the face. A morphological hallmark is the severe involvement of some parts of the body with paradoxical sparing of other similarly exposed areas.
The reaction of PMLE usually begins 12 to 24 hours after an initial exposure to light of a suddenly increased intensity. The rash persists for 7 to 10 days and resolves without scarring but may recur with subsequent intense UV light exposure.
The girl may not experience PMLE during the summer months at home in Canada because the UV light in the northern latitudes may not be intense enough to provoke the reaction. If the rash develops in the spring, it likely will become less prominent and develop less frequently with repeated light exposure over the course of the summer.