Pityriasis rosea
Pityriasis rosea is an acute, self-limited papulosquamous eruption, often linked to human herpesvirus 6 or 7 reactivation, that begins with a solitary herald patch and is followed by smaller collarette-scaled plaques along skin cleavage lines in a Christmas tree pattern. No treatment is required because the eruption self-resolves, usually within about 6 weeks; oral cetirizine 10 mg once daily can control itching, and topical glucocorticoids relieve symptoms while the rash clears on its own.
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What this article covers
- Overview
Definition: pityriasis rosea is an acute, self-limited, inflammatory papulosquamous skin eruption that is often preceded by a viral prodrome and is believed to reflect a type IV hypersensitivity reaction.
- Epidemiology
Older children and young adults are most commonly affected, though the eruption can occur at any age.
- Risk factors
Preceding viral syndrome: fever, sore throat, or malaise in the weeks before the rash is a common antecedent.
- Pathophysiology
Type IV hypersensitivity reaction: the eruption is thought to represent a delayed-type immune response rather than direct infection of the skin.
- Clinical features
Establishing features: a solitary, well-demarcated, spherical herald patch 2 to 5 cm in diameter with central clearing, closely resembling tinea corporis, typically appears first on the trunk.
- Differential diagnosis
Secondary syphilis: hyperpigmented macules or papules that involve the palms and soles, unlike pityriasis rosea, which spares the palms and soles.
- Diagnosis
The diagnostic basis is clinical recognition of the herald patch followed by the Christmas tree eruption: a solitary 2 to 5 cm herald patch, followed days to weeks later by numerous smaller…
- Management
First, reassure the patient that no treatment is necessary, since pityriasis rosea self-resolves, usually within about 6 weeks.
- Complications
Postinflammatory hyperpigmentation or hypopigmentation after the eruption clears, more apparent in darker skin.
- Prognosis
Excellent in the great majority of patients: the eruption is self-limited and resolves, usually within about 6 weeks, without scarring.
- Prevention
No preventive measure changes the incidence of pityriasis rosea, since the trigger is believed to be viral reactivation rather than an avoidable exposure.
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