Differential diagnoses: Keratinous conditions

Dr Nigel Stollery compares four keratinous conditions and offers clues for their diagnosis including actinic keratosis, ichthyosis vulgaris, seborrhoeic keratosis and hyperkeratotic horn.

Actinic keratosis


  • UV light induced, crusted skin lesion, more common in fair-skinned individuals
  • Malignant potential although low risk of change to squamous cell carcinoma (SCC)
  • Occurs on sun-exposed areas
  • More common in men
  • Increased incidence in immunocompromised individuals
  • If diagnosis in doubt, biopsy can be helpful


  • If small, emollients may be adequate
  • Various topical therapies for larger lesions
  • Cryotherapy another treatment option

Ichthyosis vulgaris


  • Most common form of inherited ichthyosis
  • Autosomal dominant transmission
  • Affects one in 250 people
  • Symptoms usually start in childhood
  • Worse in winter and temperate climates
  • Usually less severe in older age


  • Chronic condition with no cure
  • Emollients mainstay of treatment

Seborrhoeic keratosis


  • Very common wart-like lesion of unknown aetiology
  • Greasy 'stuck on' appearance
  • Can be any colour from pale to black
  • More common with increasing age, but usually starts in patients aged over 40 years
  • Often runs in families
  • No potential for malignant change


  • Treatment not usually required
  • Options include cryotherapy or curettage and cautery
  • Recurrence unlikely, but new lesions very common

Hyperkeratotic horn


  • Can arise from different lesions, such as seborrhoeic warts, actinic keratoses or viral warts
  • 15% develop from an underlying SCC
  • Induration or inflammation at base may indicate malignancy
  • Usually asymptomatic
  • Common on sun-exposed sites


  • Treatment can be undertaken with curettage and cautery
  • Base and tissue beneath should be sent for histology to exclude SCC
  • If malignancy suspected, can be referred under two-week wait rule
  • Dr Stollery is a GP in Kibworth, Leicestershire, and clinical assistant in dermatology at Leicester Royal Infirmary

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