The patient was diagnosed with pityriasis rosea (PR) on the basis of the clinical findings; a biopsy was not performed. The patient’s pruritus was treated with oral hydroxyzine and topical 1% triamcinolone ointment. She experienced itch relief with these treatments. On follow-up at 3 months, the patient’s lesions had mostly resolved with some postinflammatory hyperpigmentation.
In some patients, flu-like symptoms precede the onset of skin lesions; this has led to speculation regarding a viral etiology for PR. This prodrome, which is present in as many as half of all cases,can include mild headache, low-grade fever, joint aches, or malaise.2 Pityriasis rosea is thought to occur secondary to a systemic activation of human herpesviruses (HHV) 6 and/or HHV-7. Three cases of PR have been reported in the setting of H1N1 influenza virus infection.3 In one small study, HHV-8 was detected by polymerase chain reaction in approximately 20% of biopsy samples of lesional skin in patients with PR.4 However, most research on a viral etiology for pityriasis rosea has focused on HHV-6 and to a lesser extent HHV-7. DNA from both viruses has been isolated from PR lesions, but at varying detection rates.5,6 Furthermore, HHV-7 DNA has been isolated in as many as 14% of normal individuals without pityriasis rosea, suggesting that the presence of this virus on the skin is fairly common.7
Pityriasis rosea occurs in males and females of all ethnicities, with a slight female predominance. It is rare in young children and older adults. Most cases occur in adolescents and in adults in their twenties and early thirties. Cases occur most frequently in fall and spring.8
The herald patch of pityriasis rosea is typically solitary, but cases with multiple herald patches have been described. The herald patch can range in size from 1-10 cm and usually contains the best example of trailing scale – scale seen on the inside edge of the annular lesion. The satellite lesions of pityriasis rosea are typically papules or plaques with a collarette of scale. These lesions usually are oriented along the Langer cleavage lines, giving them a “Christmas tree” configuration when they appear on the posterior trunk.
The herald patch of pityriasis rosea can resemble tinea corporis, and if there is any doubt as to the diagnosis, potassium hydroxide examination (also known as a KOH test) and/or fungal culture should be done to rule out a fungal etiology. However, certain features of this case, particularly the subsequent development of satellite lesions, are more consistent with pityriasis rosea.
Secondary syphilis should be considered in patients who are sexually active. The lesions of secondary syphilis are not typically pruritic, and involvement of the palms and soles is common (whereas such involvement is rare in pityriasis rosea).
Like pityriasis rosea, pityriasis lichenoides et varioliformis acuta (PLEVA) is characterized by papular lesions that resolve spontaneously; the lesions of PLEVA usually evolve to vesicular, necrotic, and purpuric papules that take longer to resolve than PR lesions. The lesions of PLEVA are more erythematous, pustular, and crusting than the lesions of pityriasis rosea.
Guttate psoriasis, which occurs following streptococcal pharyngitis in over 50% of patients, does not present with a herald lesion or distribution along Langer’s lines.10 If guttate psoriasis is suspected, rapid streptococcal testing of the throat or perianal area may be considered.
Nummular eczema presents as papules that enlarge to form erythematous, lichenified plaques that measure 1-2 cm in diameter. A relatively sudden eruption, such as this patient’s, would be unusual for nummular eczema. Also, nummular eczema typically occurs on xerotic skin, more often on the extremities than the trunk.
Diagnostic tests, treatment
Most patients do not require specific therapy for pityriasis rosea. Patients should be reassured that PR is typically a self-limited disease without long-term sequelae. Pregnant patients who develop pityriasis rosea in the first trimester may be at higher risk for spontaneous abortion,although data on the subject are sorely lacking.11 Oral antihistamines are useful in reducing pruritus associated with PR, and some patients experience relief by applying a low-potency topical corticosteroid.
In more severe cases, or in cases in which the patient is greatly distressed by the lesions, both broadband and narrowband UVB phototherapy effectively improve severity of lesions and reduces symptoms.12 These observations suggest that moderate sun exposure can help to reduce severity of PR lesions and hasten their resolution, but no studies assessing the effect of sun exposure on pityriasis rosea symptoms have been performed.
Furthermore, the possible role of the HHV-6 in PR has led some investigators to explore the utility of acyclovir in managing pityriasis rosea.13 One group recently found that 400 mg of acyclovir three times per day for 7 days decreased the number of lesions and pruritus associated with pityriasis rosea, compared those seen in controls, at 1-month follow-up.13
Timely recognition of the diagnosis, consideration of mimics, and ample reassurance are appropriate when approaching this disease.
Mr. Kusari is with the division of pediatric and adolescent dermatology at Rady Children’s Hospital, San Diego, and the departments of dermatology and pediatrics, University of California, San Diego. Dr. Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego. They have no relevant financial disclosures. Email them at firstname.lastname@example.org.