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A 17-year-old young woman is brought to the office by her mom because of a rash that appeared 3 weeks ago for no apparent reason (Figures 159-1, 159-2, 159-3). She was feeling well and the rash is only occasionally pruritic. With and without mom in the room, the young woman denied sexual activity. The diagnosis of pityriasis rosea was made by the clinical appearance even though there was no obvious herald patch. The collarette scale was visible and the distribution was consistent with pityriasis rosea. The young woman and her mom were reassured that this would resolve spontaneously. At a subsequent visit for a college physical, the skin was found to be completely clear with no scarring.

FIGURE 159-1

Pityriasis rosea in a 17-year-old young woman. Lesions are often concentrated in the lower abdominal area. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 159-2

Scaling lesions seen on the buttocks of the same young woman. Note how some of the lesions are annular. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 159-3

Close-up of lesion showing collarette scale. Note how the lesions can be annular with some central clearing. (Reproduced with permission from Richard P. Usatine, MD.)


Pityriasis rosea (PR) is a common, self-limited, papulosquamous skin condition originally described in the 19th century. It is seen in children and adults. Despite the long history, its etiology remains elusive. A number of infectious etiologies have been proposed, but at present, supporting evidence is inconclusive. Pityriasis rosea has unique features, including a herald patch that is present in approximately 90% of cases1 and collarette scale, that are useful in distinguishing it from other papulosquamous eruptions.


  • Pityriasis rosea is a papulosquamous eruption of unknown etiology.

  • It occurs throughout the life cycle. It is most commonly seen between the ages of 10 and 35 years.1-4

  • The peak incidence is between 20 and 29 years of age.1-4

  • The gender distribution is essentially equal.1,2,4

  • The rash is most prevalent in winter months.1,2,4


  • The cause of pityriasis rosea is unknown, although numerous causes have been proposed.

  • It has long been suspected that it may have a viral etiology because a viral-like prodrome often occurs prior to the onset of the rash. Human herpesviruses 6 and 7 have been proposed as causes, but studies have failed to demonstrate conclusive supportive evidence.1-5 Acyclovir has been successfully used to treat PR based on the premise that ...

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