Differential diagnoses - Tinea, BCC, herald patch and fixed drug eruption

Dr Nigel Stollery explains how to recognise basal cell carcinoma among four similar lesions.

Fixed drug eruption


  • Reaction to particular medication which recurs every time the medication is taken
  • With continued exposure, multiple sites may be affected
  • Aetiology not fully understood
  • Well-defined round or oval patches of redness and swelling
  • Lesions develop 30 minutes to eight hours after taking the drug
  • Common causes include paracetamol, tetracyclines and NSAIDs


  • Lesions are self-limiting
  • Postinflammatory hyperpigmentation may occur
  • Future avoidance of causative drugs is recommended

Herald patch


  • Single lesion initially, followed by multiple smaller lesions
  • Called the herald patch because it heralds the development of pityriasis rosea
  • Occurs more commonly on the trunk
  • Has a fine surface scale and may be itchy
  • More common in autumn/winter


  • Self-limiting condition that usually settles after six to eight weeks
  • Topical antipruritics, such as calamine, may help the itch
  • In severe or widespread cases, moderately potent topical steroids may be helpful



  • Fungal infection more commonly referred to as ringworm
  • Affects all age groups
  • Expands with time, with central clearance
  • Usually very itchy, solitary lesion
  • Occurs anywhere on the body


  • Treatment includes topical or oral antifungals

Nodular basal cell carcinoma


  • The most common form of skin cancer
  • Incidence increases with age
  • More common on areas with higher UV light exposure
  • Very low metastatic potential
  • Untreated lesions can progress and become very extensive
  • Multiple lesions are common


  • Main treatment is surgical excision with Mohs micrographic surgery for more difficult lesions
  • Radiotherapy may be an option for the elderly or for those with extensive lesions
  • Dr Stollery is a GP in Kibworth, Leicestershire

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