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

Click here to take a test on this article and claim a certificate on MIMS Learning

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in

Just published

Patient satisfaction screen

How a GP practice worked with patients to stop a torrent of complaints

A GP practice has seen complaints drop from 50-plus a day to just four in 10 months...

British Army soldiers marching

How the NHS Op COURAGE service can help support veterans

Armed forces veterans often have unique health needs. Clinical staff from London...

GP consultation

Continuity of care would save millions of GP appointments each year, new study finds

GP workload would be significantly reduced if continuity of care was prioritised...

Talking General Practice logo

Podcast: Visa sponsor shortage threatens GP workforce, locum GPs struggle to find work, record appointments

The GPonline team discusses the key news stories affecting general practice in our...

RCGP sign

RCGP condemns threat to retention funding as third of GPs consider quitting

Funding for GP retention risks being stripped away to cover other financial pressures...

Professor Dame Helen Stokes Lampard

Former RCGP chair joins NHS England board

Former RCGP chair Professor Dame Helen Stokes-Lampard has joined the NHS England...