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Pathology of Mycetoma (Madura Foot ; Maduromycosis)

Dr Sampurna Roy MD

 

                                                                                                                      

 

Mycetoma is a localized chronic, and deforming granulomatous infectious disease of subcutaneous tissues, skin and bones, that is present worldwide and endemic in tropical and subtropical regions.

Mycetoma is a pathological process in which the causative agents - a fungus (eumycetoma) or a bacterium (actinomycetoma) - from exogenous source produce grains. 

Distinction between eumycetoma and actinomycetoma is very important for the treatment.

Geographic distribution:  Seen in tropical region. Example: Asia, Africa, central and south America.    

Mode of infection: Organisms are normally present in environment (soil and dust).

Infection occurs in bare-footed persons after minor penetrating skin injury inoculating soil organisms, occurring preferentially in rural areas, usually among labourers who work barefoot.

Age and sex:  Mycetoma commonly affects adults aged 20 to 40 years, predominantly males.

Site: It is a chronic, tumorous, fungal infection of deep soft tissues and bones of foot (Madura foot). Foot is most commonly affected.

Clinical presentation :

Both forms of mycetoma present as a progressive, cutaneous and subcutaneous swelling, although actinomycetoma has a more rapid course.

Multiple nodules develop which may suppurate and drain through sinuses, discharging grains during the active phase of the disease.

Pathological Features:

The inflammatory reaction in mycetoma is similar regardless of the causative agent.     

Visit:  Nocardiosis ; Actinomycosis.

Lesions contain multiple sinus tracts that usually discharge serosanguinous fluid and, at times, grossly visible granules of various colours, sized, and degrees of hardness depending on the agent involved.

Histologically, the dermis and subcutaneous tissue contain localized abscesses, each of which contains one or more granules in its centre.

Eosinophilic, clublike Splendore-Hoeppli material may border the granules.  

Between abscesses, there is extensive formation of granulation tissue, resulting in tumefaction and deformity that is often so severe as to be mistaken clinically for a neoplasm.

Infection often involve contiguous bone, resulting in destructive osteomyelitis.

Lymphatic or hematogenous dissemination from the primary subcutaneous lesion rarely occurs.

Colour of Grains (Granules) in Mycetomas: 

Eumycetomas:

Black grains: Madurella mycetomatis

Pale grains:  Petriellidium boydii , Aspergillus nidulans , Aspergillus flavus

Actinomycetomas:

Red grain: Actinomadura pelletieri

Yellow grains: Streptomyces somaliensis

Pale grains: Nocardia brasiliensis , N cavae , N asteroides, Actinomadura madurae.           

Visit:  Nocardiosis

(Adapted from Skin Pathology by Weedon: Pg 675-676.)

Morphology of the grains (granules) in Mycetomas:

Eumycetomas :

Madurella mycetomatis: Large granules (up to 5 mm or more) with interlacing hyphae embedded in interstitial brownish matrix; hyphae st periphery arranged radially with numerous chlamydospores.

Petriellidium boydii: Eosinophilic, lighter in the center; numerous vesicles or swollen hyphae ; peripheral eosinophilic fringe; other pale eumycetomas have a minimal fringe and contain a dense mass of intermeshing hyphae.

Actinomycetomas:

Actinomadura madurae: Large ( 1 - 5 mm and large) and multilobulate; peripheral basophilia and central eosinophilia or pale staining ; filaments grow from the peripheral zone.

Streptomyces somaliensis: Large ( 0.5 - 2 mm or more ) with dense thin filaments ; often stains homogeneously ; transverse fracture lines.

Nocardia brasiliensis: Small grains (approximately 1 mm); central purple zone ; loose clumps of filaments ; Gram-positive delicate branching filaments breaking up into bacillary and coccal forms ; Gram-negative amorphous matrix.

 

Diagnosis : Over 30 species have been identified as causes of mycetoma.

The grains of many of these species have overlapping morphological features.

Culture is required for accurate identification of the agent.

Diagnosis may also involve radiology, ultrasonic imaging, cytology, histology or immunodiagnosis. 

Identification of the agent is necessary as it guides the mode of treatment. 

Treatment:

Mycetoma caused by bacteria can usually be managed effectively with antibacterial medication alone, while infections with fungi require antifungal medication and surgery.

Without proper treatment, mycetoma can lead to deformity, amputation, and death.

Further reading:

Mycetoma : a review.

Molecular identification of black-grain mycetoma agents.

Translationally controlled tumor protein from Madurella mycetomatis, a marker for tumorous mycetoma progression.

Mycetoma: a thorn in the flesh.

Mycetoma: 130 cases.

Environmental occurrence of Madurella mycetomatis, the major agent of human eumycetoma in Sudan.

 

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

 

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