Pityriasis Rosea

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Introduction

Pityriasis rosea is a common rash that is thought to occur after a viral infection. Characteristically scaly and pink-coloured, pityriasis rosea is usually self-limiting and occurs most frequently among patients aged 10-35 years.1


Aetiology

While the exact cause of pityriasis rosea is unknown, it is believed to be associated with certain viruses. Chiefly, an association has been found between pityriasis rosea and human herpesvirus (HHV), in particular, HHV-6 and HHV-7.2 However, it is important to note that evidence on this association, is conflicting.3

Pityriasis rosea can occur in clusters such as schools and families; however, the rash is not contagious and there is no genetic component.


Clinical features

History

The typical history of a patient with pityriasis rosea follows a sequence of stages including prodromal symptoms, a herald patch and finally a more widespread rash.

Prodrome

The prodromal phase usually lasts a few days and includes mild fever, headache, malaise, pharyngitis and joint pain.

Herald patch

In 50% of all cases, the first dermatological presentation of pityriasis rosea is a singular salmon-coloured, scaly lesion known as a ‘herald patch’ (Figure 1). 

Widespread rash

Approximately 5-15 days after the development of the herald patch, a widespread rash appears and continues to develop over 2-6 weeks (Figures 2 & 3). This rash may be pruritic but it is not typically painful.

Clinical examination

A thorough dermatological examination is required for all patients presenting with clinical features of pityriasis rosea.

Herald patch

 Typical clinical appearances of the herald patch are as follows:

  • Site: commonly located on the trunk but may also be present on the face, feet and hands
  • Size: diameter of approximately 2-5cm
  • Configuration: a discrete, oval lesion that clears centrally leaving a collarette scale at the border
  • Colour: the lesion appears pale pink on light skin and can appear dark brown or grey on darker skin
  • Morphology: patch or plaque (if the border is raised and palpable)
herald patch
Figure 1. Herald patch4

Widespread rash

Typical clinical features of the widespread rash which follows the herald patch are as follows:

  • Site and distribution: usually found on the trunk and proximal limbs. The distribution is often symmetrical and occurs along Langer’s lines of the trunk, with an appearance resembling the branches of a Christmas tree
  • Size: smaller than the herald patch with each lesion measuring approximately 0.5-1 cm
  • Configuration: discrete lesions with a scaly outer border
  • Colour: the lesions appear pale pink on light skin, but may appear grey or dark brown on darker skin
  • Morphology: patch or plaque (if the border is raised and palpable)

The widespread rash gradually fades over 6-8 weeks but, in some people, can last up to five months.

Atypical forms of pityriasis rosea can develop such as inverse pityriasis rosea where rashes occur on the face and extremities with sparing of the trunk. See this link for more information on the less common forms of pityriasis rosea.

 


Differential diagnoses

Condition

Similarities

Differences

Guttate psoriasis

  • History: may have a previous history of Streptococcal infection
  • Location: rash commonly appears on the trunk and proximal limbs
  • Appearance: multiple pink and scaly lesions which have a small diameter of 2-10mm
  • History: no history of a herald patch preceding the widespread rash
  • Location: rash does not specifically occur along the cleavage lines of the trunk
  • Appearance: scale appears to be coarse with a silver appearance and occurs across the whole lesion as opposed to just the border

Pityriasis versicolour

  • History: rash may be itchy
  • Location: often affects the trunk and proximal limbs
  • Appearance: multiple small lesions with a fine-scale on the circumference. Often results in hypopigmentation on dark skin which can also occur in pityriasis rosea.
  • History: more commonly occurs in summer months and is associated with hot and humid conditions
  • Location: rash doesn’t specifically occur along the cleavage lines of the trunk
  • Appearance: no scale present and discrete lesions may develop and become confluent over time

Tinea corporis (ringworm)

  • History: rash may be itchy
  • Appearance: the herald patch is very similar to the patches which develop in ringworm due to its size, round shape and raised border of fine-scale
  • History: the large patch in ringworm is not followed by smaller discrete lesions. This lesion is slower growing and develops over a longer period.
  • Appearance: very similar to that of the herald patch seen in pityriasis rosea but is not similar to the widespread rash that follows

Other differential diagnoses for this type of rash include discoid eczema, secondary syphilis, HIV seroconversion, lichen planus and drug reactions.


Investigations

Pityriasis rosea is a clinical diagnosis, however, if there is clinical uncertainty, the following investigations can be performed to rule out other differential diagnoses:

  • Skin scrapings: to rule out fungal causes such as tinea corporis
  • Skin biopsy

Management

Pityriasis rosea is a self-limiting condition and should resolve without treatment, therefore management typically involves reassurance, advice and symptomatic relief.

Conservative management

Some general points of reassurance include:

  • the rash is not contagious
  • children can go to school
  • the rash should resolve on its own
  • the rash should not leave scarring

Advise the patient to avoid exposing the rash to heat such as hot showers, hot baths and vigorous exercise.

Symptomatic relief

The following therapies can be used alone or in combination to manage the symptoms associated with pityriasis rosea:

  • Emollients can be used to moisturise and soothe the skin
  • Topical corticosteroids can be used to reduce itching and inflammation 8
  • Antihistamines can be taken to reduce itching

Other management options

Consider a dermatology referral if:

  • The diagnosis is uncertain
  • The rash is atypical (e.g. a rash on the extremities or the presence of secondary features such as urticaria or petechiae)
  • The rash persists beyond three months

Severe cases of pityriasis rosea sometimes require:

  • UV-B phototherapy
  • Oral acyclovir

Severe cases should be managed by a dermatologist.


Complications

After the resolution of the rash, patients may develop temporary hypo- or hyperpigmentation but this should not cause permanent scarring. This is more common in patients with darker skin.

In some cases, the development of pityriasis rosea in the first 15 weeks of pregnancy has been associated with miscarriage, premature delivery and neonatal hypotonia.8


Key points

  • Pityriasis rosea is a common, self-limiting, pink and scaly rash which is thought to occur due to a viral infection.
  • Clinical features follow a sequence of stages including prodromal symptoms, a herald patch and finally a more widespread rash which lasts 6-8 weeks.
  • Pityriasis rosea is a clinical diagnosis and investigations are only used in the context of diagnostic uncertainty.
  • Management involves reassurance, advice and symptomatic relief including emollients, topical corticosteroids and antihistamines. UV-B phototherapy and oral acyclovir can be used in severe or persistent cases under the advice of a dermatologist.

References

  1. British Association of Dermatologists. Pityriasis rosea. Published in 2019. Available from: [LINK]
  2. Watanabe T., Kawamura T., Aquilino E.A., Blauvelt A., Jacob S.E., Orenstein J.M., Black J.B. Pityriasis Rosea is Associated with Systemic Active Infection with Both Human Herpesvirus-7 and Human Herpesvirus-6. Published in 2002. Available from: [LINK]
  3. Kempf W., Adams V., Kleinhans M., Burg G., Panizzon R.G., Campadelli-Fiume G., Nestle F.O. Pityriasis Rosea Is Not Associated With Human Herpesvirus 7. Published in 1999. Available from: [LINK]
  4. Heilman J.. A herald patch of pityriasis rosea. Licence: CC-BY-SA-3.0. Available from: [LINK]
  5. Heilman J.. Pityriasis rosea. Licence: CC-BY-SA-3.0. Available from: [LINK]
  6. Blyth M.. Pityriasis rosea in a Nigerian boy. Licence: CC-BY-3.0. Available from: [LINK]
  7. Urbina F., Das A., Sudy E.. Clinical variants of pityriasis rosea. Published in 2017. Available from: [LINK]
  8. Pityriasis rosea. Published in 2020. Available from: [LINK]

Reviewers

Dr Susan Smith

General Practitioner

Dr Mona Ebadian

Dermatology Registrar


Editor

Hannah Thomas


 

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