Psoriasis involves scaly plaques, typically on the knees, elbows, and scalp. The scales are silvery white and leave minute bleeding points on gentle scraping (Auspitz’s sign). Unlike pityriasis rosea, nail changes are often seen in psoriasis. These changes include pitting on the nail plate, onycholysis, oil drop sign, and subungual hyperkeratosis.
Pityriasis lichenoides chronica may mimic pityriasis rosea in distribution, but there are no collarette scales. Also, pityriasis lichenoides chronica does not self-resolve; it requires treatment.
Erythema annulare centrifugum is usually a single large erythematous plaque that slowly expands. There is often a history of a tick bite, and no Christmas tree distribution.
Provide symptomatic Tx
Symptomatic treatment of pityriasis rosea is generally adequate, and includes topical emollients, such as white petrolatum or mid-potency steroid creams and antihistamines for pruritus6 (strength of recommendation [SOR]: A).
Erythromycin. In one study, erythromycin 250 mg QID for 2 weeks hastened the resolution of pityriasis rosea6 (SOR: B). It was suggested that the anti-inflammatory properties and immune modulation of the drug, rather than its antibiotic effect, may have aided the clinical resolution. However, such efficacy was not substantiated in subsequent trials with erythromycin or another macrolide, azithromycin.7-10
High-dose acyclovir. Acyclovir 800 mg 5 times a day has been shown to reduce disease severity and duration in some patients with pityriasis rosea.11 However, it is not recommended as first-line therapy2 (SOR: C).
Systemic steroids should be avoided in pityriasis rosea, as they may worsen the disease.6
Is the patient of school age? If so, the evidence suggests that he or she should not be kept out of school.6
My patient
I treated this patient with a topical mid-potency steroid (betamethasone dipropionate) twice daily on the affected areas and an oral antihistamine once daily for 10 days. The patient’s symptoms and skin lesions resolved.
CORRESPONDENCE Vijay Zawar, MD, DNB, DVD, FAAD, Skin Diseases Center, 21 Shreeram Sankul, Opp. Hotel Panchavati, Vakilwadi Nashik-422001, Maharashtra, India; vijayzawar@yahoo.com