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History
A 20-year-old girl develops a rash 24 hours after commencing her holiday in the sun. The rash is itchy and red affecting her neck and forearms, there is sparing of her face and hands. The rash persists for approximately one week before settling with no scarring. She has no previous history of skin problems, although her mother had suffered a similar rash whilst on a sunny holiday.
Examination
There are clusters of confluent erythematous urticated papules and plaques on her neck (Fig. 15.1) and the extensor aspects of her arms. The rest of the skin is clear.
Questions
• What is the diagnosis?
• How would you manage this patient in the short/long term?
Medicine
This patient has polymorphic light eruption (PLE) or ‘prickly heat’. This is a very common recurring photodermatosis of unknown aetiology. It is more commonly seen in women and occurs usually about 24 hours after sun exposure as in this case. The pruritic erup-tion usually persists for 7–10 days. It is characterized by a polymorphous rash that can include erythematous macules, patches, papules, plaques, and sometimes vesicles and bullae. These typically affect the extensor forearms and ‘V area’ of the neck. The eruption classically spares the face, as in our patient. The onset of PLE usually starts in the first three decades of life and then usually occurs each spring or early summer thereafter. Many patients improve by the end of the summer but the rash occurs the following spring or following a ‘winter sun’ holiday. The degree of severity is variable. There is sometimes a family history of photosensitivity. PLE is a clinical diagnosis based on the history and it is therefore important to exclude other causes of photosensitive dermatoses such as photoallergic contact dermatitis, photo drug eruptions and lupus erythematosus. A skin biopsy can be helpful if there is any doubt.Topical steroids are the mainstay of treatment for patients presenting with the pruritic eruption of PLE. A short course of systemic corticosteroids may be required for severe attacks. Patients should be advised to protect themselves from the sun by wearing a shirt with long sleeves. Sunscreens with high factor ultraviolet (UV) A and UVB filters can be helpful in some patients. Some patients benefit from prophylactic phototherapy (narrow-band UVB) given before the onset of spring to ‘harden’ the skin and thus prevent PLE when sunlight becomes more intense.
KEY POINTS
• PLE or ‘prickly heat’ is a common eruption occurring during the spring or early summer.
• It occurs usually 24 hours after sun exposure and persists for 7–10 days.
• Other photodermatoses should be excluded in the first instance.
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