Introduction

Pityriasis rosea is a common presentation to general practice.

  • Pityriasis – causes a fine flake or flake
  • Rosea – pink coloured

It is a widespread rash caused by a viral infection (exact cause unknown – but has been linked with herpesvirus types 6 and 7), which starts of as a herald patch, and is followed by multiple other patches 1-2 weeks later and typically lasts 6-12 weeks. The lesions themselves are pink, or a dull brown colour.

It mainly affects the trunk and the upper parts of the arms and legs, which is sometimes referred to as a Christmas tree distribution

It is most commonly seen in teenagers and young adults, but can occur at any age. There is a slight female predominance. It occurs mostly during spring and autumn. It is often intensely itchy.

There is no specific treatment, but emollients, topical steroids and antihistamines may all help to receive the itch.

Presentation

Typical appearance of pityriasis rosea type rash on the trunk

Typical appearance of pityriasis rosea type rash on the trunk

The diagnosis is usually clinical. No investigations are usually required. In cases where there is diagnostic uncertainty, a skin biopsy may be performed. Clinical features can include:

  • Prodromal viral symptoms may or may not occur. They typically occur before the herald patch and may include:
    • Malaise
    • Nausea
    • Fever
    • Joint pains
    • headache
  • Itch – can be severe
  • Herald patch
    • About 75% of cases tart with a herald patch
    • Typically a single lesion 2-5cm diameter
    • Ocal or round
    • Pink coloured central area, with a brown outer rim
    • Usually on the trunk
  • Main rash
    • 1-2 weeks after the herald patch
    • Much smaller versions of the herald patch
  • Oral lesions can occur but are rare

Differentials

  • Drug rash reaction
  • Urticaria
    • Drug induced
    • Other allergic
    • Viral
  • Psoriasis
  • Tinea
  • Erythema multiforme
  • Pityriasis versicolour
  • Lichen planus
  • Secondary syphilis

Management

Managed in primary care. There is no specific treatment and the disease is self-limiting. Explain the diagnosis and reassure the patient it will disappear on its own within 3 months (usually sooner, some may take up to 5 months).

  • New areas may appear up to 6 weeks after the initial herald patch.
  • It is not contagious.
  • After the lesions resolve there may be some temporary pigment changes in the area
  • There is usually no scarring
  • The risk of recurrence is very low – about 2%

The main management problem is often itch. Evidence is very poor, but patients may report some benefit with any (or a combination of) the following:

  • Topical steroid cream – e.g. 1% hydrocortisone
  • Emollients
  • Topical menthol
  • Antihistamines

There is some evidence from a small case study that contracting pityriasis rosea early in pregnancy increases the risk of miscarriage.

Indications for referral to dermatology

  • Rash not resolving after 3 months
  • Intractable itch
  • Uncertain diagnosis

References

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