Differentiating Common Annular Lesions: Tinea Corporis vs Granuloma Annulare

A biopsy from the lesion on the hand was consistent with features of localized granuloma annulare. The patient was reassured that the condition was self-limited. The lesion on her calf, however, grew larger and new nummular and annular plaques developed that ultimately involved her legs, arms, abdomen, and back. A new diagnosis was made of generalized granuloma annulare. During the next 21⁄2 years, the patient received numerous systemic and topical treatments with little improvement in symptoms. Treatments included topical corticosteroids, intralesional and intramuscular injections of triamcinolone, biotin (vitamin H, coenzyme R), hydroxychloroquine, quinacrine, pentoxifylline, and dapsone. She is currently receiving treatment with methotrexate and folic acid, although the response has been poor. Tinea corporis and granuloma annulare are commonly seen in primary care practice. They have similar presentations, and subtle differences, and so are often misdiagnosed. A missed or erroneous diagnosis can lead to initial treatment failure and/or unnecessary therapy. Tinea corporis—a dermatophyte infection— manifests on the trunk and extremities (excluding the hair, nails, palms, soles, and groin) and often mimics benign inflammatory skin conditions, such as granuloma annulare. Tinea is generally limited to the stratum corneum and is most commonly caused by Trichophyton rubrum and Trichophyton mentagrophytes.1 The infection can be transmitted from human to human, from animal to human, and from soil to human.2 Tinea corporis typically presents as an annular erythematous plaque with a raised leading edge and scale. Clearance occurs in the center of the lesion; however, residual nodules may be scattered throughout the infected area. This creates the characteristic annular plaque that gives the disease its common name, “ringworm.” Tinea lesions also can appear as arcuate, circinate, and oval.2 When you suspect tinea corporis infection, scrape the periphery of lesions to harvest surface scale for a KOH preparation. Fungal cultures on Sabouraud agar medium may also be used to confirm the diagnosis.3 Topical azole creams—clotrimizole or miconazole—are first-line therapy for tinea corporis. Second-line topical therapies include terbinafine 1% cream, ciclopirox, and 40% urea cream.4 Granuloma annulare is a benign inflammation that classically presents with 1 or more indurated, erythematous or violaceous annular plaques on the extremities. Unlike tinea corporis, scale is absent and the lesion may or may not be pruritic. Although its etiology is unknown, 4 clinical variants have been identified: • Localized • Disseminated • Subcutaneous • Perforating While diagnosis can be made by visual examination, definitive diagnosis requires skin biopsy. Lesions are histologically characterized by necrobiotic collagen surrounded by a lymphohistiocytic infiltrate. Based on the T-cell subpopulations identified in the infiltrate, a delayed-type hypersensitivity reaction to an unknown antigen has been postulated as the precipitating event.