mycetoma pedis , or madura foot , was first described as a clinical entity by gill in 1842 , from a clinic in madurai , india . in 1880 , carter coined the term  mycetoma  .
the disease can be caused by one of two organisms , the eumyces , or true fungi ( eumycetoma ) , or actinomyces , filamentous bacteria of the order actinomycetales ( actinomycetoma ) .
it is a localized , chronic , suppurative infection characterized by exuberant granulation tissue and discharging sinuses and bone involvement later in the course of the disease .
early clinical diagnosis before the appearance of discharging sinuses is difficult as the entity may clinically mimic a low grade neoplasm or a chronic bacterial or tubercular infection .
the recently described  dot in circle sign  on magnetic resonance imaging ( mri ) is easy to recognize and specific to this condition and establishes the role of mri in early diagnosis.[35 ] we present a case of mycetoma foot that demonstrated the  dot - in - circle sign  on mri .
a 48-year - old man complained of painless swelling in the left foot that had been present for the past 6 years .
the patient had been treated with multiple courses of oral and intravenous antibiotics in a primary health center .
the patient did not respond to the treatment . at the peripheral hospital two attempts were made to incise and drain the lesion . for the past 1 month
, the patient had experienced mild dull aching pain in the foot , mainly during the night .
the patient did not mention a history of past discharge of granules from any area of the foot .
plain radiograph of the left foot showed mild soft tissue swelling with changes of chronic osteomyelitis involving the tarsal and metatarsals [ figure 1 ] .
mri was performed to characterize the lesion and to evaluate the extent of the disease .
multiple discrete , as well as , conglomerate small spherical hyperintense lesions with peripheral hypointense rim were seen .
few of these lesions showed a central tiny hypointense focus suggestive of  dot in circle  sign [ figure 2 ] .
t2-weighted fat saturated ( t2w fs ) and t1-weighted fat saturated ( t1w fs ) postcontrast images depicted the proximal extent of the lesion up to the distal half of the leg with ankle joint effusion and synovial thickening [ figure 3 ] . on the basis of mri findings , the diagnosis of mycetoma was considered and a biopsy was performed .
the final microbiological test showed the presence of curvularia lunata ( eumycetoma sp . ) [ figure 4 ] .
the patient was amputated 10 inches below the knee joint and put on 400 mg oral itraconazole daily for 6 months .
frontal radiograph shows moth eaten area of destruction involving tarsal ( white arrow ) and metatarsals ( black arrow ) with patchy erosions and mild soft tissue swelling ( yellow arrow ) .
mri t2 weighted coronal images show inflammatory changes with multiple soft tissue and osseus small hyperintense lesions with peripheral hypointense rim corresponding to mycetoma grains ( yellow arrows ) .
few of them showing  dot in circle  sign ( thicker white arrow ) .
( a ) t2 weighted fat suppressed sagittal and ( b ) t1w fat suppressed postcontrast sagittal images show extension of inflammation proximally up to distal leg with ankle joint effusion ( yellow arrow ) and synovial thickening .
 dot in circle  sign ( white arrow ) is seen in postcontrast image .
histopathology slide prepared using lactophenol cotton blue shows septated conidia which is curved at 3rd cell from the base ( yellow arrow ) confirming the diagnosis of curvularia lunata ( eumycetoma sp . ) 1500 .
mycetoma is a chronic debilitating granulomatous disease that is prevalent in tropical and subtropical regions .
the term mycetoma is a clinical entity , which applies to a chronic inflammatory process of soft tissue , usually of the foot , resulting from infection by one or more fungi or actinomycetes ( a gram - positive bacillus ) .
initially , there is formation of soft tissue swelling with induration due to underlying granulation tissue , which progresses to the formation of discharging sinuses .
the lesion may be confined to the soft tissue for years before bone involvement occurs .
the diagnosis of mycetoma should be considered when a patient presents with soft tissue lesion and discharging sinuses with or without bone involvement .
although various radiographic bone changes have been described in cases of mycetoma , bone involvement usually occurs late in the course of the disease .
noninvasive imaging with mri can characterize the soft tissue lesion of mycetoma and aid in early diagnosis .
mycetoma is characterized by the formation of aggregates of the organism , known as  grains 
this could account for the appearance observed on mri of conglomerates of small ( 25 mm ) round hyperintense lesions , representing the granulation tissue , surrounded by low - signal intensity rim , representing intervening fibrous septa .
the central low - signal intensity dot is the result of susceptibility effect caused by the presence of fungal grains .
this unique appearance known as  dot in circle sign  appears to be highly suggestive of mycetoma.[35 ] this sign was first proposed by sarris et al . , in 2003 on t2-weighted short - tau inversion recovery ( stir ) , and t1-weighted fast spin gadolinium - enhanced images in a series of two cases .
czechowski et al . , described small t1 and t2 hypointense lesion on mri caused by the susceptibility effect of the fungal grains .
however , they did not describe the  dot in circle  sign in their study . in our case ,
mri clearly depicted the conglomerate as well as discrete small round t2 hyperintense lesions with central hypointense foci in some of them .
eumycotic lesions tend to form a few cavities in the bone 1 cm in diameter , while actinomycetes often form smaller , but more numerous cavities . in a study by lewall et al .
, a moth eaten appearance caused by a combination of irregular periosteal reaction , periosteal erosion , and small cavities within bone were seen in 25% of cases of actinomycetoma , but in none of the patients with eumycetoma .
modern chemotherapeautic drugs are effective in early stage of the disease when combined with surgery .
difficulty in accurately identifying the extent of the lesion during surgery is the chief cause of recurrence .
mri can be helpful in early diagnosis and to monitor recurrence . in the absence of typical clinical features of discharging sinuses , mycetoma foot
mri could aid in the early diagnosis of this chronic infection and may differentiate it from other clinically similar conditions .
the demonstration of the organism in the lesion by biopsy and microbiological examination can be difficult . in india ,
the disease is still endemic and mri may help in early recognition and prevention of amputations that maybe required because of delayed diagnosis .
 mycetoma or maduramycosis is a localized chronic suppurative infection characterized by exuberant granulation tissue , discharging sinuses , and bone involvement later in the course of the disease . 
 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 . 
 delay in diagnosis may lead to amputation of the affected part . 
 definitive diagnosis is through biopsy and microbiological examination . 
 however , at times diagnosis may still be difficult . 
 the recently described  dot in circle  sign on magnetic resonance imaging ( mri ) is easy to recognize and highly specific . 
 we present a case of mycetoma foot with characteristic mri features . 
INTRODUCTION
CASE REPORT
DISCUSSION