Pityriasis rosea

• Pityriasis rosea:

  • Common rash
  • Thought to occur after a viral infected
  • Characteristically scaly and pink-coloured
  • Usually self-limiting
  • Most frequently occurs in patients aged 10-35
• Aetiology:

  • Associated with human herpesvirus
  • Particularly HHV-6 and HHV-7
• Clinical features:

  • Prodrome - mild fever, headache, malaise, pharyngitis, joint pain
  • Herald patch - singular salmon coloured, scaly lesion (2-5cm) that clears centrally, commonly on the trunk
  • Widespread rash - develops 5-15 days after the herald patch, smaller lesions (0.5-1cm) with a scaly outer border, often in a Christmas tree pattern along Langer's lines
• Investigations:

  • Clinical diagnosis but if there is clinical uncertainty:
  • Skin scrapings to rule out fungal causes such as tinea corporis
  • Skin biopsy
• 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:

  • Emollients
  • Topical corticosteroids - reduce itching and inflammation
  • Antihistamines - reduce itching
• Severe cases of pityriasis rosea sometimes require:

  • UV-B phototherapy
  • Oral acyclovir
• 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