Granuloma annulare is a benign, chronic, idiopathic condition characterized by papules or nodules that spread peripherally to form a ring around normal or slightly depressed skin.
Etiology of granuloma annulare is unclear but proposed mechanisms include cell-mediated immunity (type IV), immune complex vasculitis, and an abnormality of tissue monocytes. Granuloma annulare is not associated with systemic disorders, except that the incidence of abnormal glucose metabolism is increased among adults with many lesions. In some cases, exposure to sunlight, insect bites, TB skin testing, BCG vaccination, trauma, Borrelia infection, and viral infections have induced disease flares. The condition is twice as prevalent among women.
Lesions are erythematous, yellowish tan, bluish, or the color of the surrounding skin; one or more lesions may occur, most often on dorsal feet, legs, hands, or fingers. They are usually asymptomatic but may occasionally be tender. The lesions often expand or join to form rings. The center of each ring may be clear or be slightly depressed and sometimes pale or light brown. In some cases, lesions may become generalized and widespread.
Diagnosis of granuloma annulare is usually clinical but can be confirmed by skin biopsy. Unlike tinea corporis (which can cause raised annular lesions with central clearing), granuloma annulare typically has no scale and does not itch.
Usually no treatment is necessary; spontaneous resolution is common. For patients with more widespread or bothersome lesions, quicker resolution may be promoted by the use of high-strength topical corticosteroids under occlusive dressings every night, flurandrenolide-impregnated tape, topical tacrolimus (eg, 0.1% ointment bid, with dosing frequency decreasing as symptoms resolve), and intralesional corticosteroids. PUVA therapy, isotretinoin, dapsone, and cyclosporine have been reported to be successful in treating widespread disease.
Recent reports have suggested that TNF-alpha inhibitors (eg, infliximab, adalimumab), 595-nm pulsed-dye laser, excimer laser, and fractional photothermolysis are useful in managing disseminated and recalcitrant lesions.
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