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Pityriasis Rosea

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Updated May 16, 2014

Pityriasis rosea is a common, self-limited rash that typically occurs in healthy adolescents and young adults. The appearance of the rash is striking and often causes concern to the bearer and family, but it truly does resolve on its own.

Pityriasis Rosea Facts

The cause of pityriasis rosea is unknown. Studies looking for a viral or bacterial origin are not conclusive to date. Although its cause is unknown, the rash itself is associated with the following characteristics:
  • The majority occur between ages 10 and 35 years
  • Two percent of patients have a recurrence
  • It may be preceded by a recent acute infection with fever, fatigue, headache, and sore throat
  • It occurs more often in the colder months
  • It occurs in all races equally

Pityriasis Rosea Rash Appearance

Often the rash starts with a "herald patch" -- a single, 2- to 10-cm round/oval lesion which can occur anywhere but often shows up on the trunk. The herald patch often looks like ringworm. Within a few days to several weeks, smaller lesions appear mainly on the trunk but can spread to the arms, legs, and face. On light skin, the lesions are salmon-colored, and on dark skin they are hyperpigmented. These eruptive lesions are typically oval and the long axis of the oval is oriented along skin lines. A fine, tissue-like scale stays attached to the border of the lesion. A typical eruption lasts six to eight weeks, but it can persist for five months or more. The lesions may be very itchy.

Atypical Pityriasis Rosea Rash Appearance

While the above description is typical, pityriasis rosea does have several atypical forms. In younger children, pregnant women, and people with dark skin the rash can be more papular (bumpy). Vesicles and wheals can also occur in infants. A number of oral lesions can occur during a breakout. Also, at times the rash can occur on the whole body.

Pityriasis Rosea Diagnosis

Pityriasis rosea is diagnosed clinically, based on the typical appearance of the rash. If the rash is not typical, pityriasis rosea can be confused with ringworm, psoriasis, nummular eczema, and syphillis. Often a KOH test will be done to rule out ringworm and a blood test identifies syphillis. In rare cases, a lesion may need to be biopsied.

Pityriasis Rosea Treatment

It is unclear whether pityriasis rosea is contagious, but isolation is not recommended. Few good studies have been conducted to assess treatment options. One study showed that high dose erythromycin for two weeks may shorten the course. Lesions exposed to direct sunlight resolve faster than those in unexposed areas. Ultraviolet light B (UVB) therapy may reduce itching and speed resolution lesions but therapy is most beneficial during the first week of the eruption. Oral antihistamines and topical steroids may help with itching.

Sources:

Bolognia, Jean, et al., eds. "Pityriasis Rosea." Dermatology. New York: Mosby, 2003: 158-60.

Habif, Thomas. "Pityriasis Rosea" Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 246-8.

Stulberg, Daniel, and Jeff Wolfrey, MD. "Pityriasis Rosea." American Family Physician 69(2004): 87-92.

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