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Pityriasis rosea

Author: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Updated August 2014. Updated: Dr Nicole Seebacher, Department of Oncology, Oxford, United Kingdom. Copy edited by Gus Mitchell. December 2021


Pityriasis rosea — codes and concepts
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What is pityriasis rosea?

Pityriasis rosea is a self-limiting rash, which resolves in about 6–10 weeks. It is characterised by a large circular or oval "herald patch", usually found on the chest, abdomen, or back.

The herald patch is followed some time later, typically two weeks or so, by the development of smaller scaly oval red patches, resembling a Christmas tree, distributed mainly on the chest and back.

Who gets pityriasis rosea?

  • Pityriasis rosea is most common in teenagers and young adults (10–35 year-olds), however it can affect people of any age
  • Occurs very slightly more often in women
  • Approximate incidence of 0.5% to 2%
  • Most cases occur in winter

What causes pityriasis rosea?

The exact cause is not known. Viral, bacterial, and non-infective causes have been hypothesised.

Reports suggested pityriasis rosea may be caused by:

  • Viral infections
    • Herpesviruses 6 and 7 (HHV-6/7) have the strongest known association, however studies have not been confirmatory.
    • Other viral infections, such as H1N1 influenza A and COVID-19, may also be causative.
  • Drug-induced reactions
    • Many drugs have been associated, such as angiotensin-converting enzyme inhibitors, nonsteroidal anti-inflammatory drugs, hydrochlorothiazide, gold, captopril, atypical antipsychotics barbiturates, D-penicillamine, imatinib, metronidazole, isotretinoin, clozapine, and clonidine.
  • Vaccines
    • Pityriasis rosea may be triggered by the Bacillus Calmette-Guerin (BCG), H1N1, diphtheria, smallpox, hepatitis B, Pneumococcus, and COVID-19 vaccines.

What are the clinical features of pityriasis rosea?

Systemic symptoms

Except for mild to severe itching in up to 25% of patients, no systemic symptoms are typically present during the rash phase of pityriasis rosea. A few days before the rash develops, up to 69% have flu-like symptoms eg, cough or sore throat.

The herald patch

The herald patch is a single patch that appears before the generalised rash of pityriasis rosea. It is a slightly raised, oval, salmon-pink or red plaque 2–5 cm in diameter, with a peripheral scale trailing just inside the edge of the lesion, like a collaret.

See more pityriasis rosea images

Secondary rash

A few days to a few weeks later after the appearance of the herald patch, more scaly patches or plaques appear on the chest and back, most often appearing from the top down. A few plaques may also appear on the thighs, upper arms, and neck, but are uncommon on the face, scalp, palms, or soles.

These secondary lesions tend to be smaller than the herald patch. They are also oval in shape with a dry surface and the long axis of the oval lesion is often orientated around the ribs. Like the herald patch, they may have an inner collaret of scaling. Some plaques may be annular.

Pityriasis rosea patches and plaques usually follow the relaxed skin tension lines or cleavage lines (Langer lines) on both sides of the upper trunk. The rash has been described as looking like a Christmas tree in distribution. Worsening of the rash or a second wave of lesions is not uncommon before eventual spontaneous resolution of the eruption. In children the distribution and lesions are often atypical.

See more pityriasis rosea images

Atypical pityriasis rosea

Pityriasis rosea is said to be atypical when diagnosis has been difficult. Atypical pityriasis rosea may be diagnosed when the rash has features such as:

  • Atypical morphology, eg papules, vesicles, urticated plaques, purpuric, or target lesions (erythema multiforme-like)
  • Large size or confluent plaques
  • Unusual distribution of skin lesions, for example an inverse pattern, with prominent involvement of the skin folds (armpits and groin), or involvement of the limbs but the trunk is spared
  • Involvement of mucosal sites, eg mouth ulceration
  • Solitary herald patch without generalised rash
  • Multiple herald patches
  • Absence of herald patch
  • A large number of patches
  • Severe itch
  • A prolonged course of the disease
  • Multiple recurrences.

How do clinical features vary in differing types of skin?

The pityriasis rosea rash often leaves behind patches of lighter (hypopigmented) or darker (hyperpigmented) discolouration. This may be more obvious in darker-skinned people and may take months to return to normal appearance.

What are the complications of pityriasis rosea?

In most cases, pityriasis rosea is harmless. However, there are reports of complications such as:

  • Premature delivery and foetal demise during pregnancy, within the first 15 weeks of gestation
  • A severe cutaneous adverse reaction (drug hypersensitivity syndrome) due to reactivation of herpes 6/7 in association with a drug
  • Prolonged skin discolouration.

How is pityriasis rosea diagnosed?

Identification can be challenging at the onset of symptoms. There are no non-invasive tests that confirm the condition. The diagnosis is usually made clinically but may be supported by:

  • Histology — subacute dermatitis is seen on histology
  • Eosinophils are typical of drug-induced pityriasis rosea.

Blood testing for HHV6 (IgG or PCR) is not indicated because nearly 100% of individuals have been infected with the virus in childhood and commercial tests do not currently measure HHV6 activity.

If the diagnosis is uncertain, especially if the palms and soles are affected, it is important to consider the possibility of other conditions.

Table 1. Proposed diagnostic criteria for pityriasis rosea

Clinical features Criteria
Essential
  • Discrete circular or oval lesions
  • Scaling on most lesions
  • Peripheral collarette scaling with central clearance on at least two lesions
Optional (At least one of the following features)
  • Truncal and proximal limb distribution (< 10% of lesions distal to mid-upper-arm and mid-thigh)
  • Most lesions along skin cleavage lines
  • Herald patch ≥ 2 days before other lesions
Exclusion
  • Multiple small vesicles at the centre of ≥ 2 lesions
  • ≥ 2 lesions on palmar or plantar skin surfaces

Source: Zawar V, Chuh A. Applicability of proposed diagnostic criteria of pityriasis rosea:
results of a prospective case-control study in India.
Indian J Dermatol. Nov 2013

What is the differential diagnosis for pityriasis rosea?

What is the treatment for pityriasis rosea?

General measures

While pityriasis rosea is a self-limiting disease, an important goal of treatment is to control pruritus, which may be severe in 25% of patients. In addition to education and reassurance, many patients will benefit from:

Specific measures

The following therapies may help with the symptoms and speed up clearance:

  • Medium potency topical steroid creams/ointments and oral antihistamines may reduce the itch while waiting for the rash to resolve.
  • For patients with severe itching, treatment with zinc oxide, calamine lotion, and even oral steroids may be helpful. Routine use of oral steroids is not recommended due to risk for relapse after treatment and limited evidence.
  • A 7-day course of aciclovir may lead to faster resolution of lesions and help to relieve itching in severe cases
  • Extensive or persistent cases can be treated by phototherapy (narrowband ultraviolet B therapy)
  • Macrolide antibiotics were once advocated, but do not appear to be beneficial.

What is the outcome for pityriasis rosea?

Pityriasis rosea will resolve in about 6–10 weeks. Skin discolouration may persist for a few months in darker-skinned people but eventually the skin returns to its normal appearance.

Recurrence of pityriasis rosea outside the acute phase is rare (1–3%), perhaps adding weight to the suggestion that there is long-lasting immunity after a proposed infection. However, a different viral infection may trigger recurrence years later.

See more pityriasis rosea images

 

Bibliography

  • Drago F, Ranieri E, Malaguti F, Battifoglio ML, Losi E, Rebora A. Human herpesvirus 7 in patients with pityriasis rosea. Electron microscopy investigations and polymerase chain reaction in mononuclear cells, plasma and skin. Dermatol. 1997;195(4):374–8. doi:10.1159/000245991. Journal
  • Drago F, Ciccarese G, Rebora A, Parodi A. Human herpesvirus-6, -7, and Epstein-Barr virus reactivation in pityriasis rosea during COVID-19. J Med Virol. 2021;93(4):1850–1. doi:10.1002/jmv.26549. Journal
  • Drago F, Ciccarese G, Herzum A, Rebora A, Parodi A. Pityriasis Rosea during Pregnancy: Major and Minor Alarming Signs. Dermatology. 2018;234(1-2):31–6. doi:10.1159/000489879. Journal
  • Drago F, Ciccarese G, Rebora A, Parodi A. The efficacy of macrolides and acyclovir in pityriasis rosea. Ind J Dermatol Venereol Leprol. Jan-Feb 2015;81(1):56. doi:10.4103/0378-6323.148572. Journal
  • Drago F, Broccolo F, Javor S, Drago F, Rebora A, Parodi A. Evidence of human herpesvirus-6 and -7 reactivation in miscarrying women with pityriasis rosea. J Am Acad Dermatol. Jul 2014;71(1):198–9. doi:10.1016/j.jaad.2014.02.023. Journal
  • Ganguly S. A Randomized, Double-blind, Placebo-Controlled Study of Efficacy of Oral Acyclovir in the Treatment of Pityriasis Rosea. J Clin Diagn Res. 2014;8(5):Yc01-4. doi:10.7860/jcdr/2014/8140.4360. Journal
  • Jairath V, Mohan M, Jindal N, et al. Narrowband UVB phototherapy in pityriasis rosea. Indian Dermatol Online J. 2015;6(5):326–9. doi:10.4103/2229-5178.164480. Journal
  • Rodriguez-Zuniga M, Torres N, Garcia-Perdomo H. Effectiveness of acyclovir in the treatment of pityriasis rosea. A systematic review and meta-analysis. An Bras Dermatol. Sep-Oct 2018;93(5):686–95. doi:10.1590/abd1806-4841.20187252. Journal
  • Zawar V, Chuh A. Applicability of proposed diagnostic criteria of pityriasis rosea: results of a prospective case-control study in India. Ind J Dermatol. Nov 2013;58(6):439–42. doi:10.4103/0019-5154.119950 Journal

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