Localised granuloma annulare
- 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.
- 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 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.
- 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.