At a Glance - Porokeratosis of Mibelli versus Bowen's disease

Contributed by Dr Jean Watkins, a sessional GP in Hampshire


Clinical features

  • Annular plaque with raised, ridged edge develops from small brownish keratotic papule.
  • Atrophic central area.
  • May occur anywhere on the body, including mucous membranes. Most common on the limbs, especially hands and feet.
  • Usually symptomless, but may be itchy.
  • Genetic link with autosomal dominant inheritance.
  • Sometimes develops at site of injury, such as on a burn or after radiation.
  • Usually first develops in childhood or at puberty. May even occur at birth.
  • Rare condition, but more common in men. Occurs only in the fair skinned.
  • May slowly increase to reach several centimetres in size.
  • Risk of malignant change to basal cell carcinoma (BCC) or squamous cell carcinoma (SCC). Risk is particularly high in the immunosupressed.


  • No known cure.
  • Appearance may be improved with topical 5-fluorouracil, calcipotriol or imiquimod cream, cryotherapy, laser or topical or oral retinoid.
  • In view of risk of malignancy, advise regular monitoring and reporting of any change in the lesion. If in doubt, perform a biopsy and treat accordingly.
  • Sun protection is very important to prevent development of skin cancer.


Clinical features

  • In situ SCC.
  • Follows long-term exposure to UV or X-ray radiation, arsenic or HPV type 16.
  • More common in the fair skinned.
  • Good prognosis. Only 5 per cent progress to invasive SCC.
  • Erythematous, scaly plaque which gradually increases in size.
  • Unresponsive to topical steroids.
  • Usually on sun-exposed areas, especially head, neck or limbs.


  • Biopsy to confirm diagnosis.
  • Check the rest of the body for lesions.
  • Cryotherapy, curettage and cautery - although these methods do not allow for confirmation of complete lesion removal.
  • Topical 5-fluorouracil or imiquimod.
  • Radiotherapy may be advised for those in poor health or with multiple lesions.
  • Photodynamic therapy is sometimes recommended.
  • Surgical excision and histological check.

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