11.16 Pityriasis Rosea

agk’s Library of Common Simple Emergencies

Presentation

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 weeks then completely disappears. Recurrences are uncommon.

What to do:

• Reassure the patient about the benign nature of this disease. Be sympathetic and let him know that you understand how frightening it can seem.
• Draw blood for serologic testing for syphilis (e.g., VDRL). Secondary syphilis can mimic pityriasis rosea. Make a note to track down the results of the test.
• Provide relief from pruritis by prescribing hydroxyzine (Atarax) 50mg q6h or an emollient such as Lubriderm. Tepid corn starch baths (1 cup in 1/2 tub of water) may also be comforting.
• Inform the patient that he should anticipate a 6-8 week course of the disease, but to seek followup care if the rash does not resolve within 12 weeks.

What not to do:

• Do not use topical or systemic steroids. These are only effective in the most severe inflammatory varieties of this syndrome.
• Do not send off a serologic test for syphilis without assuring the results will be seen and acted upon.

Discussion

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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