Sunday, November 16, 2014



Pityriasis is a common self-limited skin eruption of unknown cause.

● Initial lesion (herald patch) precedes the eruption by approximately 1 to 2 weeks, typically measures 3 to 6 cm, and is round to oval in appearance and most frequently located
on the trunk .

● Eruptive phase follows within 2 weeks and peaks after 7 to 14 days.

● Lesions are most frequently located in the lower abdominal area. They have a salmon-pink appearance in whites and a hyperpigmented appearance in blacks .

● Most lesions are 4 to 5 mm in diameter; the center has a cigarette paper–like appearance and the border has a characteristic ring of scale (collarette).

● Lesions occur in a symmetrical distribution and follow the cleavage lines of the trunk (Christmas tree pattern)

● The number of lesions varies from a few to hundreds.

● Most patients are asymptomatic; pruritus is the most common symptom.

● History of recent fatigue, headache, sore throat, and lowgrade fever is present in approximately 25% of cases.

● Unknown, possibly viral (picornavirus)

● Tinea corporis (can be ruled out by potassium hydroxide examination; see Fig. 26–1)
● Secondary syphilis (absence of herald patch, positive serologic test for syphilis; see Fig. 226–14)
● Psoriasis
● Nummular eczema
● Drug eruption.  Medications that may cause rashes similar to pityriasis rosea include clonidine,
captopril, interferon, bismuth, barbiturates, gold, hepatitis B vaccine, and imatinib mesylate.
● Viral exanthem
● Eczema
● Lichen planus
● Tinea versicolor  the lesions are more brown and the borders are not as ovoid.

● Presence of herald lesion and characteristic rash is diagnostic.
● Skin biopsy is generally reserved for atypical cases.

The disease is self-limited and generally does not require any therapeutic intervention.

● Use oral antihistamines for patients with signifi cant pruritus.

● Use prednisone tapered over 2 weeks for patients with severe pruritus.

● Direct sun exposure or the use of UV light within the fi rst week of eruption is benefi cial in decreasing the severity of disease.

● Spontaneous complete resolution of the rash within 4 to 8 weeks

● Recurrence rare (less than 2% of cases)


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