Granuloma Annulare Mimicking Sarcoidosis: Report of Patient With Localized Granuloma Annulare Whose Skin Lesions Show 3 Clinical Morphologies and 2 Histology Patterns.

Granuloma annulare, a benign dermatosis of undetermined etiology, typically presents in a localized or generalized form. It has 3 distinctive histologic patterns: an infiltrative (interstitial) pattern, a palisading granuloma pattern, and an epithelioid nodule (sarcoidal granuloma) pattern. A man whose granuloma annulare skin lesions mimicked sarcoidosis is described. His localized granuloma annulare presented with a total of 3 lesions that each had a distinctive clinical morphology: an annular lesion of individual papules, a dermal nodule, and a linear arrangement of 3 papules. Two of his lesions showed a palisading granuloma histology pattern of granuloma annulare; however, the linear papules on his posterior neck lesion demonstrated noncaseating granulomas consistent with either the epithelioid nodule histology pattern of granuloma annulare or sarcoidal granuloma compatible with sarcoidosis. A comprehensive evaluation excluded the diagnosis of systemic sarcoidosis. Using the PubMed database, an extensive literature search was performed on granuloma annulare, epithelioid nodule, sarcoidal granuloma, and sarcoidosis. The histology patterns of granuloma annulare-emphasizing the history and differentiating features of the epithelioid nodule pattern from cutaneous sarcoidosis-were reviewed. The epithelioid nodule (sarcoidal granuloma) histology pattern of granuloma annulare is uncommon and may mimic the histology changes observed in sarcoidosis skin lesions; the absence of asteroid or other giant cell inclusions and an increase in mucin deposition between the collagen bundles favor the diagnosis of granuloma annulare. In addition, the epithelioid nodule pattern of granuloma annulare can rarely also show other histologic patterns of granuloma annulare in the same biopsy specimen or concurrently present with other clinical lesions of granuloma annulare that demonstrate a palisading granuloma, or possibly an infiltrative, histology pattern. However, the presence of an isolated skin lesion demonstrating sarcoidal granulomas--even when concurrently appearing with other lesions of granuloma annulare showing either an infiltrative or a palisading granuloma histologic pattern--may prompt the clinician to evaluate and exclude the possibility of systemic sarcoidosis.