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August 18, 2008

Red Annular Plaque on the Dorsum of the Foot—Diagnosis

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Arch Dermatol. 2008;144(8):1051-1056. doi:10.1001/archderm.144.8.1051-h

The biopsy specimens revealed grouped epithelioid granulomas with a peripheral rim of lymphocytes distributed throughout the dermis and subcutis. The granulomas were arranged arround arrectores pilorum muscles and eccrine glands, and some of them were elongated along the course of the vessels. They contained well-formed Langhans-type giant cells and multinucleate foreign body giant cells. No nerves were identified by hematoxylin-eosin and S100 protein staining. Cultures were negative for bacteria, as were stains for acid-fast bacilli. Electroneurography revealed mononeuropathy of the common peroneal nerve. The Mitsuda reaction was strongly positive. Angiotensin-converting enzyme levels, findings of chest radiography, and serum and urine calcium concentrations were normal. The results of serologic tests for syphilis (rapid plasma reagin tests and Treponema pallidum hemoagglutination assay), a tuberculin test, and mucous nasal bacilloscopy were all negative. Six months of therapy with rifampicin (600 mg/mo) and dapsone (100 mg/d) resulted in a marked improvement of the lesion, which evolved to a brownish, depressed macule. Based on the clinical and microscopic findings, the patient was diagnosed as having tuberculoid leprosy.

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