Chronic swelling of the foot
Skeletal Radiol
Chronic swelling of the foot
Dyan V. Flores 1
0 2 Amorsolo Street, Legaspi Village, Makati City, Metro Manila 1229 , Philippines
1 Department of Radiology, Makati Medical Center
2 Dyan V. Flores
-
Discussion
In the case demonstrated, radiography of the great toe (Fig. 1)
shows sclerosis and periostitis on either side of the proximal
phalanx of the first digit, and flowing sclerosis in the medial
aspect of the proximal phalanx of the second digit. Axial and
coronal T2-weighted fat-suppressed images (Fig. 2) show
ovoid, hyperintense lesions with low signal rims and faint,
tiny central dots (dot-in-circle sign), particularly in the dorsal
and medial aspects of the forefoot. Coronal (Fig. 3) and axial
(Fig. 4) T1-weighted and T1-weighted fat-suppressed
postcontrast images demonstrate enhancement of these lesions
separated by internal, non-enhancing, low-intensity tissues.
Histopathology confirms the presence of filamentous colonies
of Actinomyces (Fig. 5).
Mycetoma, first described in the Madura district of India in
1842 [
1–3
], is a clinical entity referring to a chronic,
debilitating, granulomatous disease of soft tissues, usually of the foot,
resulting from infection either with filamentous bacteria
(actinomycetoma) or true fungi (eumycetoma) [
1, 2, 4–6
]. It
is endemic in equatorial, tropical, and subtropical regions,
including the Middle East [
1, 4, 5
], but is not well known in
the USA and Europe [
5
], except in migrant populations [
7
].
Data on its prevalence have been few and far between. A
meta-analysis by van de Sande et al. in 2013 reviewed several
single-center studies from various countries and estimated a
prevalence between <0.01 to 3.49 cases per 100,000
The case presentation can be found at doi: 10.1007/s00256-017-2642-5
inhabitants, with Mexico, Sudan, and India being the most
commonly affected countries [
3
]. Patients are typically male
[
1, 3, 6
] and under 30 years old [
3, 6
]. An update from the
Mycetoma Research Center in Sudan released in 2015
predicted higher numbers in the future, with possibly more accurate
estimates of its exact global burden as more research and
surveillance programs are implemented [6].
The disease is usually slow and painless [
5
], with the
organism first lodging in the soft tissues typically as an
aftermath of skin trauma [
1, 4–6
], before multiplying and forming
colonies that spread along fascial planes to the deeper soft
tissue structures [
1, 6
]. It may be confined to the soft tissues
for years [
4–6
], but has the potential for imminent osseous
changes such as periosteal reaction and cortical erosion that
almost always commences from the outside, in contrast to the
centrifugal spread typical of bacterial osteomyelitis [
1
].
The clinical picture of mycetoma is uniform, regardless of
the causative species [
1
]. The characteristic triad includes a
painless subcutaneous mass, draining sinuses, and exuding
Bgrains^ representing either a conglomerate of fungal hyphae
[
1, 6, 7
], or bacteria in microabscesses [
8
], although these
findings may not be present until the advanced stages, when
extensive bone and soft tissue damage has already occurred
[
4
]. Moreover, constitutional symptoms and signs are rare and
may occur only after secondary bacterial infection of open
sinuses [
1
].
The available diagnostic tests for mycetoma are few and
not without limitations; early laboratory diagnosis before the
appearance of sinuses and grains is particularly challenging
[
8
]. Isolation of the fungal grains may be performed either via
a deep-seated biopsy or aspiration cytology [
2
], necessitating
the use of special stains for thorough identification of the
causative organism [
2
]. Microbiological culture provides
definitive diagnosis, but may take several weeks to months [
2, 6,
9
], with the potential for inadvertent contamination, and
Mycetoma should be part of the differential diagnosis in
any case of a chronically swollen foot, particularly one with
discharging sinuses. MRI may be important in the early
recognition of the disease to prevent progressive bone destruction
requiring surgery. The dot-in-circle sign that can be seen both
in MRI and ultrasound reflects the unique pathologic features
of the disease, is easy to recognize, is virtually pathognomonic
of mycetoma, and may suggest the possible diagnosis without
the need to wait for the histologic outcome.
Compliance with ethical standards
Grants received
None.
Disclosures None.
Conflicts of interest None.
1. Fahal A , Hassan M. Mycetoma . Br J Surg . 1992 ; 79 ( 11 ): 1138 - 41 .
2. Van de Sande W , Fahal A , Goodfellow M , Mahgoub E , Welsh O , Zijlstra E . Merits and pitfalls of currently used diagnostic tools in mycetoma . PLoS Negl Trop Dis . 2014 ; 8 ( 7 ): e2918 .
3. Van de Sande W. Global burden of human mycetoma: a systematic review and meta-analysis . PLoS Negl Trop Dis . 2013 ; 7 ( 11 ): e2550 .
4. Bouziane M , Amriss O , (...truncated)