Photo Rounds

Smooth plaque on ankle

A 17-year-old boy presented to Dermatology with a 6-month history of a pink, round, raised plaque on the lateral lower leg. He had tried topical terbinafine for a month without improvement. The patient’s mother had a history of cutaneous lupus and worried that he might be developing it, too.

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Smooth plaque on ankle

A 4-mm punch biopsy of the annular border confirmed a diagnosis of localized granuloma annulare (GA).

There is a long list of differential diagnoses for annular patches and plaques; it includes tinea corporis and important systemic diseases such as sarcoidosis and Lyme disease. Clinical features of GA include annular, minimally scaly patches to plaques with central clearing on extensor surfaces in children and adults. Sometimes GA is much more widespread. Often, the diagnosis can be made clinically, but a punch biopsy of the deep dermis will confirm the diagnosis by showing palisading or interstitial granulomatous inflammation, necrobiotic collagen, and often mucin.

GA is a common inflammatory disorder with an uncertain etiology. Localized GA affects children and adults and is often self limiting. It may, however, last for months or years before resolving. Disseminated disease is much more recalcitrant with few good treatment options if topical steroids or phototherapy fails. Treatment for localized disease is much more successful with topical or intralesional steroids.

Trauma can cause a localized plaque to resolve; a lesion may resolve soon after a biopsy is performed. Possible related conditions include diabetes, thyroid disease, hepatitis C, and hyperlipidemia; but there is no consensus on focused screening. Similarly, associations or nonassociations with malignancy in adults have been cited, but evidence is lacking.1

In this case, the patient and his family were reassured that the diagnosis wasn’t serious. In a single visit, he received a series of 6 to 7 injections of 10 mg/mL triamcinolone which led to resolution of the lesion in 4 weeks.

Text courtesy of Jonathan Karnes, MD, medical director, MDFMR Dermatology Services, Augusta, ME. Photos courtesy of Jonathan Karnes, MD (copyright retained).

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