Pityriasis rosea is an acute self-limiting papulomacular skin rash that is common in children and young adults. It is a frequent presentation in primary care and dermatology settings. Pityriasis rosea is characterized by the appearance of a large reddish-pink, oval-shaped patch referred to as a "herald patch." It proceeds to an eruption of smaller pink oval patches on the back or trunk, arms and legs.1
The cause of pityriasis rosea is unclear. Fungal, bacterial and allergic causes have been ruled out.2 Several theories have been introduced to explain why pityriasis rosea occurs and why it is so common.
Several behavioral characteristics of pityriasis rosea support the possible involvement of a viral component. Often, pityriasis rosea occurs in groups of people, mimicking an influenza epidemic.1 Pityriasis rosea is an acute, self-limiting rash occurring only once in a person's lifetime. This also is suggestive of a viral component; it is theorized that affected patients build up immunity to it. If the virus is reactivated, experts believe it could occur as a result of alteration in the immune system of the infected person.2
Another factor that suggests a viral origin is the occurrence of a mild illness just before the herald patch presents.1 The viruses commonly associated with pityriasis rosea are human herpesvirus 7 (HHV-7)3 and human herpesvirus 6 (HHV-6).4 HHV-7 and HHV-6 occur in other disorders such as roseola, mononucleosis syndromes, focal encephalitis and pneumonitis.5 HHV-6 and HHV-7 are not present in all patients who develop pityriasis rosea, but in one study almost 70% of patients with the lesions carried HHV-7.2
A leading theory is that HHV-7 or HHV-6 is acquired at an early age and lays latent in CD4+ T cells and saliva.2 The viral particles infect the cells between the skin and blood vessels, causing cell rupture and destruction of the dermal and epidermal tissues.2 It is unclear what initiates reactivation of HHV.2
Prolonged medication therapy has been suggested as a cause of pityriasis rosea, and this theory has been the subject of considerable debate. Medications such as captopril (Capoten), metronidazole (Flagyl), clonidine (Catapres), certain barbiturates, gold, bismuth subsalicylate (Pepto-Bismol), omeprazole (Prilosec), levamisole (Ergamisol), and hydroxychloroquine (Plaquenil) have been linked to pityriasis rosea.2 Vaccines for Bacillus Calmette-Guerin, hepatitis B and pneumococcus have also been linked to pityriasis rosea.2
Pityriasis rosea may occur in patients who experience high levels of stress or depression.2 Stress can weaken the immune system, also contributing to an increased susceptibility to infection.2
The typical presentation of pityriasis rosea begins with a pink or red macule or papule. It usually appears on the trunk or the back. The patch slowly expands over a couple of days, taking an oval shape measuring 2 cm to 10 cm in diameter.2 This patch is referred to as the "herald" patch because it heralds the eruption of smaller lesions, which is considered the primary plaque.2 Some patients may experience multiple patches.3 Herald patches usually present with white scaling in the middle of the patch, described as crinkled or as cigarette paper.6 Five percent of patients experience symptoms such as generalized weakness, malaise and fever with onset of the herald patch.3
The appearance of a smaller oval-shaped macule or small papules or plaques occurs up to 21 days later.2 The lesions can be 5 mm to 10 mm in diameter.7 Typically, they present on the arms, neck, trunk, back and legs. These lesions can appear over 2 weeks.3 In a small number of patients, lesions may appear on the palms of the hands or the soles of the feet.3
The classic sign of pityriasis rosea is the presence of back lesions that follow a pattern described as a Christmas or fir tree.6 The lesions appear in a long bilateral parallel pattern that follows the skin cleavages of the body (Langer's lines).2 If the lesions appear on the abdomen, they are arranged transversely, also following the patient's skin cleavages.1
Some instances of pityriasis rosea occur inversely; the rash is on the extremities but absent on the trunk and back.1 The reason for this variation is unclear. The lesions are similar to that of the herald patch, slightly lighter in color, and appear in a similar collarette scale.2
Twenty five percent of patients with pityriasis rosea develop pruritus with the rash eruption, and it can be severe.2,7 Sweating and tight clothing can intensify pruritus symptoms.2 Another 25% of patients with pityriasis rosea are asymptomatic.2
Pityriasis rosea can mimic several skin disorders, and a thorough history can help rule them out. Because pityriasis rosea can sometimes appear on the soles or palms of the hands and feet, secondary syphilis is an infection that should be excluded. Sexual history, the presence of new partners and use of protection against sexually transmitted infection should be part of the history gathering for adolescents and adults. Obtain serologic tests for syphilis and a venereal disease panel to rule out a syphilis diagnosis.
Because pityriasis rosea may have multiple lesions that can coalesce and exhibit central clearing, the possibility of tinea corporis should be explored. Tinea corporis lesions are not as widespread and numerous as of those of pityriasis rosea.6 Culturing of the lesion and the presence of fungus can help rule out pityriasis rosea.6 Tinea versicolor or pityriasis versicolor can also be ruled out via culture and the presence of yeast or hyphae with KOH preparation. Tinea versicolor scales are not visible unless scraped.6
Eczema is another skin disorder that is often misdiagnosed as pityriasis rosea. Pruritus associated with pityriasis rosea can be severe, with eczema, lichenification, erythema and inflamed skin papules.
An adverse reaction to a medication can also lead a clinician to misdiagnose pityriasis rosea. Drug interactions have a faster onset then pityriasis rosea and lack a herald's patch.2 Another distinguishing feature is that lesions from a drug interaction are much larger, lack a collarette scale and are more likely to group together.
The clinician should begin the diagnostic process with a complete skin history and a review of all medications. Patients should be asked about recent fevers, malaise or mild illness. Sick contacts should also be assessed: What was the illness and what is that person's relationship to the patient?
Patient occupation should be explored to assess exposure and risk for illnesses such as upper respiratory tract infections.2 The history should attempt to pinpoint the onset of the lesions and the presence of the herald patch before the smaller lesions emerged.
Pityriasis rosea most often develops in immunocompromised patients, children, adults younger than 20, black people and women.3 According to epidemiologic studies, pityriasis rosea is more prevalent in the spring and fall, but it can occur at any time of year.2,3
The physical examination should include a complete skin assessment. Small salmon-pink lesions with scales and central clearing must be present before considering a diagnosis of pityriasis rosea. Close examination is a priority, because not all lesions associated with pityriasis rosea exhibit scaling and central clearing. Black patients who present with pityriasis rosea may have hyperpigmentation and, more frequently, oral lesions accompanied by lymphadenopathy.3 Therefore, assessment of the oral mucosa should also be considered.3
This image shows a herald patch for pityriasis rosea. For more information, visit www.aad.org.
Photo copyright American Academy of Dermatology
No laboratory tests or biopsy assists in the diagnosis of pityriasis rosea.1 Sedimentation rate and complete blood count may help rule out or confirm an infectious process. They can also help with diagnosis of pityriasis rosea.
Patients who present with pityriasis rosea can be asymptomatic. Patients with the rash are not contagious. No medications or therapies can eradicate pityriasis rosea. It is self-limiting and resolves within 4 to 8 weeks.2 The focus of treatment is therefore on symptom management.
Patients who develop pruritus in the course of pityriasis rosea outbreak may experience some relief with application of a topical lotion that contains menthol or calamine.3 Lotions should contain at least 0.5% menthol or calamine to be effective against pruritus. Over-the-counter emollients can also help soothe the skin. In patients with intense itching, a topical steroid or an antihistamine may be beneficial. Dark-skinned patients with severe pruritus may also benefit from a short course of oral corticosteroids.8
Erythromycin may help shorten the course of severe pityriasis rosea due to its anti-inflammatory effects.2 The typical regimen for this use is in divided doses delivered over 14 days.7 In one study, 73% of patients who took erythromycin experienced complete clearance of pityriasis rosea within 2 weeks.2 Ampicillin should be avoided in patients with pityriasis rosea because this drug has been associated with an increase in the eruption of the rash.2
Ultraviolet B phototherapy
Ultraviolet phototherapy can help with immediate pruritus symptom management if it is initiated within 24 hours of presentation. Ultraviolet therapy speeds up the rate of clearance of the rash if delivered early.3
Obtaining ultraviolet rays from sun exposure is not recommended. Prolonged exposure to the sun can worsen the symptoms of pruritus and can cause skin burn.3 Hyperpigmentation and dryness of the skin are the side effects associated with ultraviolet therapy.2 This therapy is reserved for severe cases, patients who are refractory to the treatments described earlier, and patients with recurrent episodes of the rash.2
Some studies show that high doses of acyclovir promote clearance of pityriasis rosea.8 Acyclovir has been used in the treatment of human herpesvirus and helps hasten the clearance of lesions in the infection. Due to the high dose of acyclovir available for herpes (800 mg dosed five times daily) and its high price tag, treatment with anti-herpes therapy is not usually warranted or prescribed.2
Patient Education Paramount
Patient education and reassurance are important in the management of pityriasis rosea. Educating the patient that pityriasis rosea is not contagious or infectious and that it will resolve in a specific time period helps allay fears and strengthen the patient-clinician relationship and interaction. Although pityriasis rosea is a self-limiting illness, it is imperative that patients return for follow-up to ensure stable illness course and that no complications occur. Follow-up and biopsy of the lesion should occur quickly if the rash does not clear within 6 to 8 weeks.1 In such cases, other diagnoses need to be considered.1
1. Stulberg DL, Wolfrey J. Pityriasis rosea. Am Fam Physician. 2004;69(1):87-91.
2. González LM, et al. Pityriasis rosea: an important papulosquamous disorder. Int J Dermatol. 2005;44(9):757-764.
3. Hartley AH. Pityriasis rosea. Pediatr Rev. 1999;20(8):266-269.
4. Kwon NH, et al. A novel influenza a (H1N1) virus as a possible cause of pityriasis rosea? J Euro Acad Dermatol Venereol. 2011;25(3):368-369.
5. Rantala H, et al. Human herpesvirus-6 associated encephalitis with subsequent infantile spasms and cerebellar astrocytoma. Dev Med Child Neurol. 2000;42(6):418-421.
6. McPhee SJ, Papadakis MA. Pityriasis rosea. In: Current Medical Diagnosis & Treatment. 50th ed. San Francisco, CA: McGraw-Hill Medical; 2010: 110-111.
7. Turchin I, et al. Dermacase. Pityriasis rosea. Can Fam Physician. 2004;50(41):49-50.
8. Mavarkar L. Pityriasis rosea occurring during acyclovir therapy. Indian J Dermatol, Venereol Leprol. 2007;73(3):200-2001.
Cortnee Kelly is an adult nurse practitioner at Middletown Cardiovascular Associates in Middletown, Ohio. She has completed a disclosure statement and reports no relationships related to this article.