Benign, self-limiting condition. Aetiology unknown. So named as the lesion resembles a raised ring, or annulus.
- Palisading histocytes surrounding necrobiotic collagen (rheumatoid nodules show a more amorphous, fibrinoid centre)
- Usually superficial to mid-dermis, but sometimes deeper in children
- Absence of plasma cells (presence of plasma cells may suggest rheumatoid nodule or necrobiosis lipodica).
Diagnosis and Management
It tends to be confused with dermatophytosis - tinea - but does not itch so much, and does not respond to anti-fungal agents nor do skin scrapings show fungal elements or grow fungus in culture. The lesions do not fluoresce, but fluorescence is often not obvious with fungal lesions either.
Corticosteroids have been used, topically.