Annular Lesions: Diagnosis and Treatment.

Annular lesions can present in a variety of diseases. Knowledge of the physical appearance and history of presentation of these skin findings can help in the diagnosis. A pruritic, annular, erythematous patch that grows centrifugally should prompt evaluation for tinea corporis. Tinea corporis may be diagnosed through potassium hydroxide examination of scrapings. Recognizing erythema migrans is important in making the diagnosis of Lyme disease so that antibiotics can be initiated promptly. Plaque psoriasis generally presents with sharply demarcated, erythematous silver plaques. Erythema multiforme, which is due to a hypersensitivity reaction, presents with annular, raised lesions with central clearing. Lichen planus characteristically appears as planar, purple, polygonal, pruritic papules and plaques. Nummular eczema presents as a rash composed of coin-shaped papulovesicular erythematous lesions. Treatment is aimed at reducing skin dryness. Pityriasis rosea presents with multiple erythematous lesions with raised, scaly borders, and is generally self-limited. Urticaria results from the release of histamines and appears as well-circumscribed, erythematous lesions with raised borders and blanched centers. Annular lesions occur less commonly in persons with fixed drug eruptions, leprosy, immunoglobulin A vasculitis, secondary syphilis, sarcoidosis, subacute cutaneous lupus erythematosus, and granuloma annulare.