Pityriasis rosea

ICD-10: L42

Pityriasis rosea (also known as "Pityriasis rosea Gibert") is a skin rash. It is non-dangerous but may inflict

substantial discomfort on some people. Classically, it begins with a single "herald patch" lesion, followed in 1 or

2 weeks by a generalized body rash lasting about 6 weeks.

Pityriasis rosea is a common, self-limited rash that typically occurs in healthy adolescents and young adults. The appearance of the rash is striking and often causes concern to the bearer and family, but it truly does resolve on its own.

Pityriasis Rosea Facts

The cause of pityriasis rosea is unknown. Studies looking for a viral or bacterial origin are not conclusive to date. Although its cause is unknown, the rash itself is associated with the following characteristics:

The majority occur between ages 10 and 35 years

Two percent of patients have a recurrence

It may be preceded by a recent acute infection with fever, fatigue, headache, and sore throat

It occurs more often in the colder months

It occurs in all races equally.

Pityriasis Rosea Rash Appearance

Often the rash starts with a "herald patch" -- a single, 2- to 10-cm round/oval lesion which can occur anywhere but often shows up on the trunk. The herald patch often looks likeringworm. Within a few days to several weeks, smaller lesions appear mainly on the trunk but can spread to the arms, legs, and face. On light skin, the lesions are salmon-colored, and on dark skin they are hyperpigmented. These eruptive lesions are typically oval and the long axis of the oval is oriented along skin lines. A fine, tissue-like scale stays attached to the border of the lesion. A typical eruption lasts six to eight weeks, but it can persist for five months or more. The lesions may be very itchy.

Atypical Pityriasis Rosea Rash Appearance

While the above description is typical, pityriasis rosea does have several atypical forms. In younger children, pregnant women, and people with dark skin the rash can be morepapular (bumpy). Vesicles and wheals can also occur in infants. A number of oral lesions can occur during a breakout. Also, at times the rash can occur on the whole body.

Signs and symptoms

Pityriasis rosea on human torso

The symptoms of this condition include:

An upper respiratory tract infection may precede all other symptoms in as many as 69% of patients

A single, 2- to 10-cm oval red "herald" patch appears, classically on the abdomen. 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 foracne. Rarely, it

does not become present at all.

7-14 days after the herald patch, large patches of pink or red, flaky, oval-shaped rash appear on the

torso. In 6% of cases an inverse distribution may occur, with rash mostly on the extremities. The more

numerous oval patches generally spread widely across the chest first, following the rib-line in a

characteristic "christmas-tree" distribution (Langer’s lines). Small, circular patches may appear on the back

and neck several days later. It is unusual for lesions to form on the face, but they may appear on the

cheeks or at the hairline.

About one-in-four people with PR suffer from 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.

The rash may be accompanied by low-grade fever, headache, nausea and fatigue. Over-the-counter

medications can help manage these.

Causes

The cause of pityriasis rosea is not certain, but its clinical presentation and immunologic reactions suggest

a viral infection as a cause. Also, HHV-7 is frequently found in healthy individuals, so its etiologic role is

controversial.

Diagnosis

A herald patch of pityriasis rosea which started before the rest of the lesion as failed treatment with antifungals

Pityriasis rosea is diagnosed clinically, based on the typical appearance of the rash. If the rash is not typical, pityriasis rosea can be confused with ringworm, psoriasis, nummular eczema, and syphillis. Often a KOH test will be done to rule out ringworm and a blood test identifies syphillis. In rare cases, a lesion may need to be biopsied.

Experienced practitioners may make the diagnosis clinically. If the diagnosis is in doubt, tests may be

performed to rule out similar conditions such asringworm, guttate psoriasis, nummular or discoid eczema, drug

eruptions, other viral exanthems, and especially secondary syphilis. A biopsy of the lesions will show

extravasated erythrocytes within dermal papillae and dyskeratotic cells within the dermis.

Treatment

No treatment is usually required.

It is unclear whether pityriasis rosea is contagious, but isolation is not recommended. Few good studies have been conducted to assess treatment options. One study showed that high dose erythromycin for two weeks

may shorten the course. Lesions exposed to direct sunlight resolve faster than those in unexposed areas. Ultraviolet light B (UVB) therapy may reduce itching and speed resolution lesions but therapy is most beneficial during the first week of the eruption. Oral antihistamines and topical steroids may help with itching.

Oral antihistamines or topical steroids may be used to decrease itching. 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, itching and scratching should be avoided. Irritants such as soap should be avoided, too; a soap

containing moisturizers (such as goat's milk) may be used, however, any generic moisturizer can help to

manage over-dryness.

Direct sunlight makes the lesions resolve more quickly. According to this principle, medical treatment

with ultraviolet light has been used to hasten resolution, though studies disagree whether it

decreases itching or not. UV therapy is most beneficial in the first week of the eruption.

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. Two percent of patients have recurrence.

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. It is more common in spring.

PR is not viewed as contagious, though there have been reports of small epidemics in fraternity houses and

military bases, schools and gyms.