Dot-in-Circle Sign - A Diagnostic MRI Sign for "Madura Foot"

Abstract

Mycetoma is a slowly progressive localised, granulomatous, subcutaneous tissue infection common among adult males aged 20 - 50 years. The causing agents include both bacteria (actinomycetoma) and fungi (eumycetoma). This chronic infection was described in literature as Madura foot and eventually mycetoma, due to its etiology. Early clinical diagnosis before the appearance of sinuses and grains (aggregates of organism surrounded by granulation tissue, which are discharged from the draining sinuses) is difficult. Early diagnosis is important due to the therapeutic implications. Although biopsy and microbiological cultures provide definitive diagnosis. Delay in diagnosis may lead to amputation of the affected part. The recently described "dot-in-circle" sign on magnetic resonance imaging (MRI) is easy to recognise and highly specific. We present a case of histologically proven mycetoma with characteristic MRI features.