Pityriasis rosea is a common, acute, self-limited papulosquamous eruption of possible viral aetiology. The aim of this study was to describe the profile of pityriasis rosea seen at a referral skin centre in Singapore.A retrospective chart review was conducted of all the patients with a diagnosis of pityriasis rosea seen during 1996. There were 368 patients; their ages ranged from 9 months to 82 years with a peak in the 20 to 29 years age group. There were slightly more males (1.2:1). The clinic incidence was 6.5 per 1000 cases. No ethnic predilection was noted and cases were seen evenly throughout the year. About a quarter of the patients gave a history of a viral infection shortly before or during the occurrence of the rash. Most cases had a typical truncal distribution. The herald patch was observed in 63 patients (17%). Inverse distribution involving mainly the extremities were seen in 22 cases (6%) and eczematised lesions were noted in 20 cases (5.4%). The two main differential diagnoses considered were tinea infection and secondary syphilis. A fungal scrape and a rapid plasma reagin test were done in 58 and 59 patients, respectively, and the results were negative. Treatment was symptomatic and consisted of topical steroids and antihistamines. Thirty patients (8%) were given oral prednisolone for extensive eruptions. The pattern of pityriasis rosea in Singapore is similar to that reported in other countries except for a male predominance and absence of monthly variation. A lower incidence and an older group of patients were also seen in our series as compared to African patients.
Pityriasis rosea is a common, self-limited disorder of unknown but suspected viral aetiology, that develops abruptly with few or no prodromal symptoms. Classically, the first sign is the presence of a single lesion, 2 to 5 cm in diameter known as a “herald patch”.
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