Photodistributed chickenpox mimicking polymorphic light eruption
Authors: G.E.N. Osborne, J.L.M. Hawk
Journal: British Journal of Dermatology (2000)

S ir, Photodistributed varicella infection is rare and the typical polymorphism of varicella lesions may not be present. 1 Unfamiliarity with this phenomenon may lead to misdiagnosis as a specific photodermatosis of non‐infectious aetiology, e.g. polymorphic light eruption. We report an adult with a relatively monomorphic photolocalized cutaneous varicella eruption occurring a day after an episode of subtropical sunbathing, where the clinical features most resembled those of polymorphic light eruption; however, subsequent vesicle fluid analysis indicated the true diagnosis. We wish to highlight this rare differential diagnosis of polymorphic light eruption, as the clinical distinction is of great importance when therapy with a systemic steroid is considered. If administered erroneously in chickenpox, this could lead to life‐threatening disseminated varicella infection; 2 in addition, unsuspected chickenpox could lead to the infection of many others. A 31‐year‐old woman presented to the dermatology out‐patient department with a 2‐day history of a rapidly evolving, widespread, slightly pruritic eruption on the trunk, face and limbs. This had arisen the day she returned to the U.K. from a spring holiday in Turkey where, a day earlier, she had sustained mild sunburn while sunbathing. There were no previous or present constitutional features besides a mild frontal headache present following the onset of the rash. There was no relevant past medical or drug history and the patient denied previous unusual sunlight sensitivity or a knowledge of prior chickenpox infection. Examination revealed a densely distributed monomorphic, almost confluent eruption composed of erythematous 1–2 mm diameter papules, with only a few vesicles, each surmounting a papule, localized to the trunk and, to a lesser extent, the face and limbs. There were no pustules, crusts or erosions. The eruption had a clear photodistribution, showing a striking demarcation with normal skin at the margins of the bathing suit area, where there was a complete absence of lesions. There were no lesions on the scalp or oral mucosa. The remaining physical examination was unremarkable. The history of very recent sunbathing and the presence of a pruritic, predominantly monomorphic, apparent photoeruption following intense sunlight exposure strongly suggested a diagnosis of a first episode of polymorphic light eruption. As the rash was extensive and clearly troubling the patient considerably, treatment with a systemic steroid was considered on the proviso that subsequent vesicle fluid analysis was negative for herpes simplex or varicella zoster virus. However, a Tzank preparation from the fluid showed multinucleated epidermal cells, suggesting the presence of herpes, while antigen‐specific immunofluorescence of the vesicle fluid then confirmed the presence of varicella zoster virus. Oral aciclovir treatment was therefore commenced, after which, over the subsequent few days, lesions also gradually developed at sites protected from sunlight. Within 10 days the patient had made a complete recovery.