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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 e.g. Asia, Africa, central and south America.
Vist:
Infectious Disease Online
Mode of infection:
Organisms are normally present in environment (soil & 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.
Image
Link1 ;
Image Link2 .
Histologically, the dermis and subcutaneous tissue contain localized
abscesses, each of which contains one or more granules in its centre.
Image Link1 ;
Image Link2
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 , A flavus
Actinomycetomas:
Red grain:
Actinomadura pelletieri
Yellow
grains:
Streptomyces somaliensis
Pale grains:
Nocardia brasiliensis , N cavae , N
asteroides, Actinomadura madurae.
Visit:
Nocardiosis
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(Adapted from Skin
Pathology by Weedon: Pg 675-676.)
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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.
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