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.
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).
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.
Madura Foot
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
1. X-ray Examination: The right foot tarsal bones and surrounding soft tissue lesion area appear to have chronic osteomyelitis-like changes, including local bone destruction, sclerosis, and irregular bone resorption. The bone cortex shows signs of erosion, and the lesion exhibits cavity-like or honeycomb-like alterations. The surrounding soft tissues are noticeably swollen.
2. MRI Examination: Multiple round or quasi-round high-signal nodular lesions are visible in the soft tissue, with some showing low-signal centers, forming the typical “Dot-in-circle” sign, indicating nodular lesions and their internal pathogen clumps. The lesion boundaries within the soft tissue are relatively clear, and the bone is significantly involved, showing bone destruction and abnormal bone marrow signals.
Considering the patient’s symptoms (long-term ulcers, blackish discharge, no history of diabetes, suspected fungal or actinomycotic infection), occupational background (agricultural work, potential barefoot walking), and the typical radiological manifestation (“Dot-in-circle” sign), the most likely diagnosis is:
Mycetoma (Madura foot).
Further distinction between actinomycotic (Actinomycetoma) or fungal (Eumycetoma) etiology requires culture or histopathological examination. In addition, histological or microbiological evaluation of the local lesion can further confirm the pathogen type, providing guidance for precise treatment.
1. Medication and Surgical Treatment:
- Actinomycetoma (Actinomycotic Mycetoma): Mainly involves surgical debridement in combination with long-term antibiotic therapy. Sulfonamides, tetracyclines, or other broad-spectrum antibiotics are commonly chosen, with treatments lasting several months to over half a year.
- Eumycetoma (Fungal Mycetoma): Partially responsive to antifungal agents, though outcomes can be less favorable, necessitating surgical intervention. For smaller or localized lesions, surgical debridement may be performed first, followed by prolonged azole-based antifungal therapy.
- In cases of extensive lesions causing severe erosion and destruction, amputation may be necessary depending on the situation.
2. Rehabilitation and Exercise Prescription:
Given the chronic foot lesion and bone destruction, early treatment should involve reduced weight-bearing, potentially with braces or crutches, and careful management of the wound and surgical site. Once infection is under control or once postoperative braces are removed, the following principles can be applied to gradually resume activity:
Throughout the rehabilitation process, closely monitor the wound status. Adjust the exercise program based on inflammation or ulcer healing. If increased redness, discharge, or pain occurs, reassess promptly and reduce or pause exercise intensity.
Disclaimer: This report is a reference analysis based on the provided imaging and clinical information. It is not a substitute for an in-person consultation or professional medical advice. Specific treatment and rehabilitation plans should be developed by a professional medical team after comprehensive evaluation of the patient’s actual condition.
Madura Foot
