Pityriasis rosea

Pityriasis rosea on torso

The symptoms of this condition include:

• An upper respiratory tract infection may precede all other symptoms in as many as 69% of patients.[4]
• A single, 2- to (rarely) 10-cm oval red "herald" patch appears, classically on the abdomen.[5] Occasionally, the "herald" patch may occur in a 'hidden' position (in the armpit, for example) and not be noticed immediately. The "herald" patch may also appear as a cluster of smaller oval spots, and be mistaken for acne. Rarely, it does not become present at all.
• 7–14 days after the herald patch, many small (5–10 mm) patches of pink or red, flaky, oval-shaped rash appear on the torso. The more numerous oval patches generally spread widely across the chest first, following the rib-line in a characteristic "christmas-tree" distribution. Small, circular patches may appear on the back and neck several days later.[5]
• In 6% of cases an "inverse" distribution may occur, with rash mostly on the extremities.[6] In children, presentation can be atypical or inverse, and the course is typically milder.[7][8]
• About one in four people with PR have mild to severe symptomatic itching. (Moderate itching due to skin over-dryness is much more common, especially if soap is used to cleanse the affected areas.) The itching is often non-specific, and worsens if scratched. This tends to fade as the rash develops and does not usually last through the entire course of the disease.[9]
• The rash may be accompanied by low-grade fever, headache, nausea and fatigue.[10]

The cause of pityriasis rosea is not certain, but its clinical presentation and immunologic reactions suggest a viral infection as a cause. Some believe it to be a reactivation[11] of herpes viruses 6 and 7, which cause roseola in infants.[12][13][14][15]

A herald patch of pityriasis rosea which started before the rest of the lesion and was initially mistaken for a fungal infection

Experienced practitioners may make the diagnosis clinically.[16] If the diagnosis is in doubt, tests may be performed to rule out similar conditions such as Lyme disease, ringworm, guttate psoriasis, nummular or discoid eczema, drug eruptions, other viral exanthems.[16][17] The clinical appearance of pityriasis rosea is similar to that of secondary syphilis, and rapid plasma reagin testing should be performed if there is any clinical concern for syphilis.[18] A biopsy of the lesions will show extravasated erythrocytes within dermal papillae and dyskeratotic cells within the dermis.[16]

A set of validated diagnostic criteria for pityriasis rosea[19][20] is as follows:

A patient is diagnosed as having pityriasis rosea if:

1. On at least one occasion or clinical encounter, he / she has all the essential clinical features and at least one of the optional clinical features, and
2. On all occasions or clinical encounters related to the rash, he / she does not have any of the exclusional clinical features.

The essential clinical features are the following:

1. Discrete circular or oval lesions,
2. Scaling on most lesions, and
3. Peripheral collarette scaling with central clearance on at least two lesions.

The optional clinical features are the following:

1. Truncal and proximal limb distribution, with less than 10% of lesions distal to mid-upper-arm and mid-thigh,
2. Orientation of most lesions along skin cleavage lines, and
3. A herald patch (not necessarily the largest) appearing at least two days before eruption of other lesions, from history of the patient or from clinical observation.

The exclusional clinical features are the following:

1. Multiple small vesicles at the centre of two or more lesions,
2. Two or more lesions on palmar or plantar skin surfaces, and
3. Clinical or serological evidence of secondary syphilis.

The condition usually resolves on its own, and treatment is not required.[21] Oral antihistamines or topical steroids may be used to decrease itching.[16] Steroids do provide relief from itching, and improve the appearance of the rash, but they also cause the new skin that forms (after the rash subsides) to take longer to match the surrounding skin color. While no scarring has been found to be associated with the rash, scratching should be avoided. It's possible that scratching can make itching worse and an itch-scratch cycle may develop with regular scratching (that is, you itch more because you scratch, so you scratch more because you itch, and so on). Irritants such as soaps with fragrances, hot water, wool, and synthetic fabrics should be avoided. Lotions that help stop or prevent itching may be helpful.[21][22]

Direct sunlight makes the lesions resolve more quickly.[16] According to this principle, medical treatment with ultraviolet light has been used to hasten resolution,[23] though studies disagree whether it decreases itching[23] or not.[24] UV therapy is most beneficial in the first week of the eruption.[23]

A 2007 meta-analysis concluded that there is insufficient evidence for the effectiveness of most treatments.[25] Oral erythromycin was found to be effective for treating the rash and relieving the itch based on one early trial; however, a later study could not confirm these results.[4][25][26]

In most patients, the condition lasts only a matter of weeks; in some cases it can last longer (up to six months). The disease resolves completely without long-term effects. Two percent of patients have recurrence.[27][28]

The overall prevalence of PR in the United States has been estimated to be 0.13% in men and 0.14% in women. It most commonly occurs between the ages of 10 and 35.[16] It is more common in spring.[16]

PR is not viewed as contagious,[29][30] though there have been reports of small epidemics in fraternity houses and military bases, schools and gyms.[16]

• Pityriasis circinata - a localized form of pityriasis rosea that affects the axillae and groin
• Pityriasis - for list of similarly named flaky skin conditions
• List of cutaneous conditions

• DermNet viral/pityriasis-rosea

• American Academy of Dermatology - Pityriasis Rosea

• American Osteopathic College of Dermatology