Pityriasis rosea. This benign and self-limited eruption occurs most often in spring and autumn. Most patients are adolescents and young adults, but the disorder is not unusual in children and may even occur during infancy. In its classic form, pityriasis rosea follows a specific and predictable clinical course. The first solitary lesion is a circle or oval of erythema and scaling. As it develops to its full size of up to 2-10 cm, this so-called herald patch may easily be mistaken for a lesion of tinea corporis. The chest and upper thigh are common locations for the herald patch but any area, including the abdomen and back, may be involved. We don't know the exact cause, but Pityriasis is thought to occur after a viral infection and self resolves, it can take up to 10 weeks for the rash to clear.. A typical herald patch is shown here.
Color Atlas of Pediatric Dermatology Samuel Weinberg, Neil S. Prose, Leonard Kristal Copyright 2008, 1998, 1990, 1975, by the McGraw-Hill Companies, Inc. All rights reserved.
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