Etiology, Diagnosis, and Therapeutic Management of Granuloma Annulare

An Update

Laura A. Thornsberry; Joseph C. EnglishIII

Disclosures

Am J Clin Dermatol. 2013;14(4):279-290. 

In This Article

4 Diagnosis

4.1 Differential Diagnosis

The differential diagnosis of GA is broad; therefore, a skin biopsy is recommended for clinicopathological correlation when GA is suspected. The differential diagnosis includes sarcoidosis, necrobiosis lipoidica, interstitial granulomatous dermatitis, tinea, nummular eczema, psoriasis, lupus, leprosy, verruca vulgaris, eruptive xanthomas, and granulomatous mycosis fungoides.[60,61] Subcutaneous lesions must be distinguished from rheumatoid nodules, sarcoidosis, panniculitis, and infection in the proper clinical context.

4.2 Diagnosis and Histological Features

The histology is essential for the diagnosis of GA, and is classically characterized by dermal palisading granulomas with central degeneration of collagen, the presence of mucin, and a lymphohistiocytic infiltrate. The presence of mucin is the key histological feature to distinguish GA from other non-infectious granulomatous diseases. Sarcoidosis is characterized by non-caseating epithelioid granulomas with a subtle infiltrate and an absence of mucin. Necrobiosis lipoidica is differentiated from GA by the diffuse involvement of the dermis with horizontal layers of granulomas and degenerated collagen, the presence of plasma cells, and the absence of mucin. The histiocytes in GA have been described in four patterns: (1) interstitial pattern, (2) surrounding the palisading granulomas, (3) nodules that resemble sarcoidosis, and (4) a mixed pattern.[62] Collagen necrosis is usually more prominent in localized GA than generalized GA. Perforating GA differs from other variants histologically by the presence of collagen being expelled through the epidermis.[63] Rarely, perineural infiltration may be seen.[64] Vasculitis changes are not expected with GA.[62]

4.3 Diagnostic Tests

Given the reported systemic associations with GA, further evaluation for underlying diseases can be considered, especially in patients with generalized annular, disseminated papular, atypical generalized, or recalcitrant generalized GA. In the appropriate clinical context and on the basis of clinical suspicion, a thorough review of systems, risk factors, and physical examination, the dermatologist can consider further laboratory and/or imaging evaluations for underlying conditions such as DM, malignancy, thyroid disease, and dyslipidemia (Table 1). Additionally, all patients should be encouraged to complete age-appropriate cancer screening.

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