CASE 14374 Published on 31.01.2017

Madura Foot

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Roopkamal Sidhu, Pinkal Patel, Umangg Parikh, Mukeshchandra Shah.

Department of Radiodiagnosis
Dr. M.K.Shah Medical College & Research Centre, Ahmedabad, India.
Email: roopkamal27@gmail.com
Patient

59 years, male

Categories
Area of Interest Bones, Soft tissues / Skin ; Imaging Technique Digital radiography, Image manipulation / Reconstruction, Ultrasound, MR
Clinical History
A 59-year-old farmer presented with complaint of long-standing swelling over lateral aspect of the right foot with recurrent non-healing ulcers & gradual black pus discharge. No past history of TB and not a known case of diabetes. He was being treated with injectible antibiotics and oral antifungals.
Imaging Findings
A clinical image (Fig. 1) of the lateral aspect of the right foot elicits painful swelling with multiple discharging nodules. The largest nodule appears black.

X-ray right ankle AP (Fig. 2a) and oblique (Fig. 2b) views show soft tissue swelling over lateral aspect and sclerosis of calcaneum with multiple patchy lucent areas, resembling a moth-eaten appearance. Sclerosis & periosteal reaction was noted at the lateral aspect of fifth metatarsal bone as well as talus.

Ultrasound (Fig. 3) with high frequency linear probe at local site demonstrates multiple hypoechoic well-defined lesions with hyperechoic centres, consistent with "Dot-in-circle" sign (arrows).

T2W axial (Fig. 4a) image shows "Dot-in-circle" sign, rounded hyperintensity (representing granulation tissue), surrounded by a low signal intensity rim (representing fibrous septa) with a hypointense dot (representing susceptibility loss due to fungi) in the centre (red arrows). A sagittal (Fig. 4b) image shows oedema (yellow arrows) with moth eaten appearance of the calcaneum (green arrows).
Discussion
A. Background: Mycetoma is a chronic granulomatous fungal infection, endemic in the tropics, mainly Africa, Mexico and India. It is named after Madurai in India, where it was originally described in 1842. It commonly affects the feet, hands, back and gluteal region. It is caused by either actinomycetes or eumycetes group of fungi [1].

B. Clinical perspective: It typically presents in farmers who walk barefoot in dry, dusty conditions. Minor trauma allows pathogens to enter the skin from the soil and gradually form discharging granulomas with subsequent involvement and destruction of underlying bones. It is important to differentiate between actinomycetoma and eumycetoma because of the different responses to treatment. Meticulous diagnosis of the fungus can save the weight-bearing function of the foot as well as circumvent the need for surgical amputation [2].

C. Imaging perspective: X-ray shows changes of chronic osteomyelitis with soft tissue involvement, sclerosis, cavitation, cortical erosion and destruction of underlying bones. Conventional radiographs are used to determine whether bones are affected and to identify the limits of lesions [3].

MRI is useful for visualizing soft tissue involvement and bone destruction. Multiple small spherical hyperintense granulomatous lesions separated by tissues of low signal intensity appear, with hypointense foci of fungal hyphae, consistent with “Dot-in-circle”, which makes this appearance characteristic of mycetoma. This feature is also noted on ultrasound. Actinomycetoma more often delineate soft tissue microabscesses, bony periosteal reaction and reactive sclerosis, while eumycetoma frequently exhibit soft tissue macroabscesses with bone cavitation. However, culture studies remain the gold standard for species identification [3].

D. Outcome: Surgical debridement followed by prolonged antibiotic therapy for several months is required for actinomycetoma. Eumycetomas are only partially responsive to anti-fungal therapy but can be treated by surgery due to their normally well circumscribed nature. Surgery in combination with azole treatment is the recommended regime for small eumycetoma lesions in the extremities. Amputation may be required in recurrent cases [4].

E. Teaching points:
- Typical clinical history with clear radiological signs can lead to early diagnosis of Madura foot and prevent deformity/remodelling.
- It is important to identify the causative species for implementing the correct line of treatment.
- Dot-in-circle sign is characteristic of maduramycosis on MRI and ultrasound.
Differential Diagnosis List
Madura Foot
Chronic bacterial osteomyelitis
Tuberculosis
Final Diagnosis
Madura Foot
Case information
URL: https://www.eurorad.org/case/14374
DOI: 10.1594/EURORAD/CASE.14374
ISSN: 1563-4086
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