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11.16 Pityriasis Rosea


Patients with this benign disorder often seek acute medical help because of the worrisome sudden spread of a rash that began with one local skin lesion. This "herald patch" may develop anywhere on the body and appears as a round 2-6 cm mildly erythematous scaling plaque. There is no change for a period of several days to two weeks; then the rash appears, composed of small (l-2cm), pale, salmon-colored, oval macules or plaques with a coarse surface surrounded by a rim of fine scales. The distribution is truncal with the long axis of the oval lesions running in the planes of cleavage of the skin (parallel to the ribs). The condition may be asymptomatic or accompanied by varying degrees of pruritis and, occasionally mild malaise. The lesions will gradually extend in size and may become confluent with one another. The rash persists for 6-8 week then completely disappears. Recurrences are uncommon.

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Pityriasis rosea is seen most commonly in adolescents and young adults during the spring and fall seasons. It is probably a viral syndrome. The "herald patch" may not be seen in 20-30% of the cases and there are many variations from the classic presentation described. Other diagnostic considerations besides syphilis include tinea corporis, seborrheic dermatitis, acute psoriasis, and tinea versicolor.

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from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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Craig Feied, MD
Mark Smith, MD
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