At a Glance - Granuloma annulare vs tinea incognito

Contributed by Dr Jean Watkins, a sessional GP in Hampshire.

Localised granuloma annulare


Clinical features

  • Benign inflammatory dermatosis.
  • Aetiology unknown.
  • Occasionally associated with diabetes mellitus or thyroid disease (more often in generalised granuloma annulare).
  • Tends to mainly affect children and young adults.
  • Red, flat-topped papules coalesce to form a rough, annular lesion over weeks or months.
  • Usually on the dorsal surfaces of the hands or feet or extensor surfaces of the limbs.
  • Usually symptomless but may be painful and tender.
  • After resolution, may tend to recur at the same site.

Management

  • Reassure the patient that this is a benign condition that should resolve spontaneously within about two years.
  • If in doubt, skin scraping will help to exclude ringworm.
  • Diagnosis can usually be made on clinical grounds but biopsy if necessary.
  • Potent topical steroids, under occlusion if necessary, or intralesional steroids.
  • Small plaques can be treated with cryotherapy.

Tinea incognito

Clinical features

  • Tinea is caused by a dermatophyte fungal infection, most commonly Trichphyton rubrum.
  • If misdiagnosed and treated with a topical steroid, the appearance of the rash is altered (tinea incognito).
  • Typically, tinea presents with an erythematous scaling annular plaque or plaques with a more marked inflammatory edge and central clearing.
  • Following the use of a topical steroid there is initial improvement and less itching.
  • The rash then becomes more extensive, has a less raised margin, more pustules develop and it is less scaly.
  • Purpura, telangiectasia and skin atrophy may develop if a potent topical steroid has been used for a long time.

Management

  • Skin scrapings for microscopy and culture confirm diagnosis.
  • It may be necessary to stop the steroid for a few days if a positive result is to be obtained, although there may initially be some rebound inflammation.
  • For localised lesions a topical antifungal cream such as miconazole, econazole or terbinafine twice daily for up to two weeks may suffice.
  • For more widespread lesions an oral antifungal agent such as terbinafine 250mg daily for four weeks should clear it.

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