Pityriasis rosea

Pityriasis rosea is a type of skin rash.<ref name=NORD2015/> Classically, it begins with a single red and slightly scaly area known as a "herald patch".<ref name=NORD2015/> This is then followed, days to weeks later, by an eruption of many smaller scaly spots; pinkish with a red edge in people with light skin and greyish in darker skin.<ref name=Li2021>Template:Cite book</ref> About 20% of cases show atypical deviations from this pattern.<ref name=BMJ2015/> It usually lasts less than three months and goes away without treatment.<ref name=BMJ2015>Template:Cite journal</ref> Sometimes malaise or a fever may occur before the start of the rash or itchiness, but often there are few other symptoms.<ref name=BMJ2015/>

While the cause is not entirely clear, it is believed to be related to human herpesvirus 6 (HHV6) or human herpesvirus 7 (HHV7).<ref name=BMJ2015/> It does not appear to be contagious.<ref name=BMJ2015/> Certain medications may result in a similar rash.<ref name=BMJ2015/> Diagnosis is based on the symptoms.<ref name=NORD2015/>

Evidence for specific treatment is limited.<ref name=BMJ2015/> About 1.3% of people are affected at some point in time.<ref name=BMJ2015/> It most often occurs in those between the ages of 10 and 35.<ref name=NORD2015>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The condition was described at least as early as 1798.<ref name=Bol2003>Template:Cite book</ref>

Signs and symptoms

File:Pityriasisfront.jpg

Pityriasis rosea on torso

The symptoms of this condition include:

• Recent upper respiratory tract infections in 8–69% of patients have been reported by some studies.<ref>Template:Cite journal</ref><ref name=pmid10642679>Template:Cite journal</ref>
• Occasionally, prodromal flu-like symptoms, including headache, joint pain, mild fever, and fatigue, as well as gastrointestinal symptoms such as nausea, diarrhea, or vomiting, and feeling generally unwell, precede other symptoms.<ref name="D 2016">Template:Cite journal</ref><ref name="JAAD 1986">Template:Cite journal</ref>
• In most cases, a single, 2 to 10 cm (1" to 4") oval red "herald" patch appears, classically on the trunk or neck, having an appearance similar to ringworm.<ref name=":1">Template:Cite journal</ref> 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.
• After the herald patch appears, usually some days or weeks later, a rash of many small (5–10 mm; Template:Frac" to Template:Frac") pink or red, flaky, oval or round spots appear. They are mostly situated on the trunk and upper limbs. They follow the skin's cleavage lines, which on the upper chest and back produce a characteristic "christmas-tree" distribution.<ref name=":1" />
• In 6% of cases an "inverse" distribution may occur, with rash mostly on the extremities.<ref name=pmid10672397>Template:Cite journal</ref> In children, presentation can be atypical or inverse, and the course is typically milder.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
• 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.<ref name=aad>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

About a fifth of cases have an atypical form, with significant variations in symptoms including the size, distribution, morphology, and evolution of the lesions.<ref name="WJCC 2017">Template:Cite journal</ref><ref name="JTAD 2012">Template:Cite journal</ref> In addition to typical papules and scales, forms appearing as very large plaques (pityriasis rosea gigantea), urticaria, large blisters, patches resembling erythema multiforme, oral lesions, and various other appearances have been noted.<ref name="JAAD 1986" /> A vesicular form can mimic chicken pox.<ref name="JTAD 2012" /><ref name="JAAD 1986" /> Variations in distribution include inverted forms, with rashes on the face or extremities without appearing on the trunk, as well as more uncommon versions localized to the armpits, groin, or extremities (pityriasis rosea circinata et marginata of Vidal) or unilateral spread.<ref name="JAAD 1986" />

Causes

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<ref>Template:Cite book</ref> of herpes viruses 6 and 7, which cause roseola in infants,<ref name=pmid24947696>Template:Cite journal</ref><ref name=dermnetnz>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=Allen2009>Template:EMedicine</ref><ref name="MagroCrowson2007">Template:Cite book</ref> though some investigations have found no evidence of this.<ref name = kempf>Template:Cite journal</ref>

Diagnosis

File:Heraldpatch2.jpg

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.<ref name = habif>Template:Cite book</ref> Classical symptoms are usually straightforward to recognize, but the wide range of atypical forms may cause difficulty for the clinician in diagnosing some cases.<ref name="WJCC 2017" /> Misdiagnosis by nondermatologists is not uncommon.<ref name="D 2016" /> 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.<ref name = habif /><ref name = horn>Template:Cite journal</ref> The clinical appearance of pityriasis rosea in some cases is similar to that of secondary syphilis, and rapid plasma reagin testing should be performed if there is any clinical concern for syphilis.<ref>Template:Cite book</ref> A biopsy of the lesions will show extravasated erythrocytes within dermal papillae and dyskeratotic cells within the dermis.<ref name = habif />

A set of validated diagnostic criteria for pityriasis rosea<ref name = jeadv>Template:Cite journal</ref><ref name = idr>Template:Cite journal</ref> is as follows:

A patient is diagnosed as having pityriasis rosea if:

1. On at least one occasion or clinical encounter, the patient 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, the patient does not have any of the exclusional clinical features.

The essential clinical features are the following:Template:Citation needed

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:Template:Citation needed

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:Template:Citation needed

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.

Treatment

The condition usually resolves on its own within 6 to 8 weeks, and management is symptomatic.<ref>Template:Cite book</ref> Oral antihistamines or topical steroids may be used to decrease itching.<ref name="habif" /> 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 is possible that scratching can make itching worse and an itch–scratch cycle may develop with regular scratching (that is, the patient itches more because they scratch, so they scratch more because they itch, and so on). Irritants such as soaps with fragrances, chlorinated water, wool, and synthetic fabrics should be avoided. Lotions that help stop or prevent itching may be helpful.<ref name=":0">Template:Cite journal</ref><ref>Template:Cite journal</ref>

Direct sunlight makes the lesions resolve more quickly.<ref name = habif /> According to this principle, medical treatment with ultraviolet light has been used to hasten resolution,<ref name = arndt >Template:Cite journal</ref> though studies disagree whether it decreases itching<ref name = arndt /> or not.<ref name = leen>Template:Cite journal</ref> UV therapy is most beneficial in the first week of the eruption.<ref name = arndt />

A updated 2019 meta-analysis concluded that compared with placebo or no treatment, oral acyclovir probably leads to increased good practitioner-rated rash improvement, its effect on itch was inconclusive.<ref name=":2">Template:Cite journal</ref> 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.<ref name=pmid10642679/><ref name=":2" /><ref name="pmid18246696">Template:Cite journal</ref>

Prognosis

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. In a ten-year epidemiological study of 939 people in the United States, less than two percent had a recurrence.<ref name = chuang>Template:Cite journal</ref>

Epidemiology

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.<ref name = habif /> It is more common in spring.<ref name = habif />

PR is not viewed as contagious,<ref name = aocd>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=dd>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> though there have been reports of small epidemics in fraternity houses and military bases, schools and gyms.<ref name = habif />

See also

• 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

External links

• Template:DermNet
• American Academy of Dermatology - Pityriasis Rosea
• American Osteopathic College of Dermatology