Diagnosis: Granuloma annulare
Granuloma annulare (GA) is a self-limited cutaneous disorder predominantly seen in women that affects children and adults. The cause is unknown. Inciting factors can include herpes zoster infection, sun exposure, medications, and trauma.
Several clinical variants exist. Localized GA is the most common form, often presenting in the first three decades of life as an asymptomatic, erythematous, annular plaque with a firm border and central clearing localized to the wrists, ankles, and dorsal hands or feet. Generalized GA accounts for 15% of reported cases and presents in the fourth to seventh decades of life as multiple asymptomatic or pruritic skin-colored or erythematous papules and plaques on the trunk and extremities. Subcutaneous GA is more common in children and presents as multiple painless nodules on the scalp or extremities. Patch GA can be localized or generalized. Perforating GA presents as asymptomatic erythematous papules that evolve into yellow, umbilicated papules with a clear-to-white discharge.
Histopathologically, an interstitial or palisading pattern is seen with a dermal lymphohistiocytic infiltrate, degenerated collagen, and mucin deposition (visualized with alcian blue or colloidal iron stains). The interstitial pattern presents in the majority of cases.
Diagnosis of GA is predominantly clinically based. When the diagnosis is questionable or the presentation is atypical, biopsy is useful. Granuloma annulare is often self-limiting and resolves within 2 years, although recurrence is possible. First-line therapy for localized GA includes high-potency topical corticosteroids or intralesional corticosteroids. Other treatments include cryotherapy, phototherapy, and topical tacrolimus. For generalized GA, topical or intralesional corticosteroids may be used for select lesions. Topical calcineurin inhibitors, light therapy, hydroxychloroquine, isotretinion, and dapsone also have been reported as treatments in the literature.