Pityriasis Rosea

Essentials of Diagnosis

• Oval, fawn-colored, scaly eruption following cleavage lines of trunk

• Herald patch precedes eruption by 1–2 weeks

• Occasional pruritus

General Considerations

• Common mild, acute inflammatory disease that is 50% more common in women

• The eruption usually lasts 6–8 weeks and heals without scarring

Demographics

• Young adults are principally affected, mostly in the spring or fall

Symptoms and Signs

• Diagnosis is made by finding one or more classic lesions

• The lesions consist of oval, fawn-colored plaques up to 2 cm in diameter

• The centers of the lesions have a crinkled or "cigarette paper" appearance and a collarette scale, ie, a thin bit of scale that is bound at the periphery and free in the center

• Only a few lesions in the eruption may have this characteristic appearance, however

• Lesions follow cleavage lines on the trunk (so-called Christmas tree pattern), and the proximal portions of the extremities are often involved

• Herald patch precedes eruption by 1–2 weeks

• Pruritus, if present, is usually mild

• Variants that affect the flexures (axillae and groin), so-called inverse pityriasis rosea, and papular variants, especially in black patients, also occur

Differential Diagnosis

• Secondary syphilis

• Tinea corporis (body ringworm)

• Seborrheic dermatitis

• Tinea versicolor (pityriasis versicolor)

• Lichen planus

• Guttate or plaque psoriasis

• Nummular eczema

• Drug eruption

• Viral exanthem

• Clinical

Medications

• See Table 6–2

• Often requires no treatment

• In darker-skinned individuals, in whom lesions may remain dyspigmented for some time, more aggressive management may be indicated

• Oral acyclovir may improve the rash appearance

• The most effective management consists of daily UVB treatments for a week, or a short course of prednisone

• Topical corticosteroids of medium strength (triamcinolone 0.1%) and oral antihistamines may also be used if pruritus is bothersome

Prognosis

• Usually acute self-limiting illness that disappears in about 6 weeks

When to Refer

• If there is a question about the diagnosis, if recommended therapy is ineffective, or if specialized treatment is necessary