Pityriasis Rosea

Key Points
Skin condition, primarily of teens and young adults, which typically affects torso, but may appear on the thighs, neck or upper arms
Exact cause is unknown, but mat be linked to antecedent upper respiratory viral infection, which itself is usually asymptomatic
Initially consists of a solitary plaque with scaly borders, oval or round in shape, which then spreads to other areas in crops

Pityriasis rosea is a skin condition which first appears on the torso, usually as a solitary oval or rounded plaque, and may spread in crops to the thighs, neck or upper arms. The primary plaque is known as the "herald patch", as it heralds the onset of the rash. Subsequently, similar smaller lesions appear in other areas of the trunk and spread outward, typically following the lines of the ribs. These lesions may form a "christmas tree" pattern on the back. Lesions are pink in color, scaly and accompanied by itching in some cases.The rash typically resolves in 6 to 12 weeks, and does not generally leave scars or marks. The rash is not generally accompanied by a feeling of unwellness.

The exact cause of pityriasis rosea is unknown, but it often appears in association with prior respiratory viral infection, though once the rash appears, is not infectious. The condition typically appears in young adults or teens, and only rarely recurs in affected persons.

Differential Diagnosis (Other conditions with similar appearance)
Drug eruptions
Pityriasis rubra pilaris
Psoriasis, Guttate

Seborrheic Dermatitis
Lichen Planus
Syphilis
Nummular Dermatitis
Tinea Corporis
Pityriasis alba
Tinea Versicolor
Pityriasis lichenoides

Diagnosis
Key Points
Diagnosis based characteristic appearance of the rash, in a young adult
Other testing may be performed to rule out other conditions, such as a blood test to rule out syphilis if indicated, or a skin biopsy if the diagnosis is questionable

Treatment
Condition resolves spontaneously even without treatment, although rarely may persist for months
Avoiding irritants such as soap is recommended
Treatment typically consists of topical medications to relieve itching and use of moisturizers to minimize dryness
*Severe cases may require more aggressive therapies, such as phototherapy performed in the dermatologists office, or a course of oral acyclovir
OTC Options: moisturizers to help with itching and dryness,such as Sarna lotion; soap substitutes for bathing (e.g. Purpose, Cetaphil, CeraVe)

Pityriasis rosea eventually resolves completely, with no residual sequelae. Avoiding irritants such as soap is recommended, as they may worsen the condition. Treatment typically consists of the administration of topical steroids to relieve itching and application of moisturizers to minimize dryness. In persistent, widespread, or intensley itchy cases, more aggressive therapies such as narrowband UVB phototherapy may be used. Additionally, in early stage cases, use of acyclovir pills may hasten resolution.