Pityriasis Rosea

Pityriasis rosea is an acute exanthematous eruption with a distinctive morphology and often with a characteristic self-limited course. First, a single (primary, or "herald") plaque lesion develops, usually on the trunk, and 1 or 2 weeks later a generalized secondary eruption develops in a typical distribution pattern; the entire process remits spontaneously in 6 weeks.

Epidemiology and Etiology

Age of Onset

10 to 43 years, but can occur rarely in infants and old persons.

Season

Spring and fall.

Etiology

Herpes virus type 7 is suspected.

History

Duration of Lesions

A single herald patch precedes the exanthematous phase; which develops over a period of 1 to 2 weeks. Pruritus—absent (25%), mild (50%), or severe (25%).

Physical Examination

Skin Lesions

Herald Patch

80% of patients. Oval, slightly raised plaque 2 to 5 cm, salmon-red, fine collarette scale at periphery; may be multiple

Pityriasis rosea Overview of exanthem of pityriasis rosea with the herald patch shown in the inset. There are papules and small plaques with oval configuration that follow the lines of cleavage. The fine scaling of the salmon-red papules cannot be seen at this magnification, while the collarette of the herald patch is quite obvious. Inset: Herald patch. An erythematous (salmon-red) plaque with a collarette scale on the trailing edge of the advancing border. Collarette means that scale is attached at periphery and loose toward the center of the lesion

Exanthem

Fine scaling papules and plaques with marginal collarette (Fig. 7-1). Dull pink or tawny. Oval, scattered, with characteristic distribution with the long axes of the oval lesions following the lines of cleavage in a "Christmas tree" pattern (Image 7-1). Lesions usually confined to trunk and proximal aspects of the arms and legs. Rarely on face.

Atypical Pityriasis Rosea

Lesions may be present only on the face and neck. The primary plaque may be absent, may be the sole manifestation of the disease, or may be multiple. Most confusing are the examples of pityriasis rosea with vesicles or simulating erythema multiforme. This usually results from irritation and sweating, often as a consequence of inadequate treatment (pityriasis rosea irritata).

Differential Diagnosis

Multiple Small Scaling Plaques

Drug eruptions (e.g., captopril, barbiturates); secondary syphilis (obtain serology); guttate psoriasis (no marginal collarette); erythema migrans with secondary lesions; erythema multiforme; and tinea corporis.

Laboratory Examination

Dermatopathology

Patchy or diffuse parakeratosis, absence of granular layer, slight acanthosis, focal spongiosis, microscopic vesicles. Occasional dyskeratotic cells with an eosinophilic homogeneous appearance. Edema of dermis, homogenization of the collagen. Perivascular infiltrate mononuclear cells.

Course

Spontaneous remission in 6 to 12 weeks or less. Recurrences are uncommon.

Management

Symptomatic

Oral antihistamines and/or topical antipruritic lotions for relief of pruritus. Topical glucocorticoids. May be improved by UVB phototherapy or natural sunlight exposure if treatment is begun in the first week of eruption. Short course of systemic glucocorticoids.