A.K. Kumar K T
Mycetoma is a chronic tropical disease caused by a diverse group of fungi (Eumycetoma) and filamentous bacteria (Actinomycetoma). This article comprises of a series of four interesting cases of mycetoma of the foot.
Actinomycetoma, Eumycetoma, foot
Mycetoma is a chronic, progressive, subcutaneous granulomatous infection caused by a diverse group of fungi (Eumycetoma) and filamentous bacteria (Actinomycetoma). It is characterized by a triad of tumefaction, draining sinus tracts and purulent discharge. [1,2]
It was first described by John Gill in 1842 in Madras, India, hence giving the term Madura foot. It is endemic in tropical regions and the most common site of occurrence is the foot (approximately 70% of cases). This series describes four cases of mycetoma of the foot where histopathology played a key role in distinguishing Eumycetoma from Actinomycetoma.
A 41-year-old male with multiple swellings and draining sinuses over the left foot for the past eight years. Above knee amputation of the left lower limb was performed and sent for histopathological evaluation. Grossly, the entire limb measured 78 cm and the foot measured 27 cm. The lateral and posterior aspect of the leg showed multiple discharging sinuses (Figure 1).
Figure 1. Specimen of an above knee amputation of the left lower limb.
The lateral and posterior aspects of the leg show multiple discharging sinuses. The left foot which is grossly swollen and shows multiple ulcers, the largest measuring 2 x 1.2 cm with yellowish discharge.
A 55-year-old male with a non tender swelling over the lateral aspect of the right foot for the past eight years. Excision of the swelling was done and sent to histopathology.
A 43-year-old male with a swelling over the right foot for the past four years associated with purulent discharge. On wound debridement, granules were seen in the discharge. Tissue was sent for histopathological evaluation.
Histological examination of these three cases showed many colonies composed of a denselytangled mass of thin filamentous, blue stained colonies. Peripherally, club shaped eosinophilic Splendore-Hoeppli reaction was seen (Figure 2).
Figure 2. shows many colonies of thin, filamentous, blue stained organisms. Peripherally, eosinophilic Splendore-Hoeppli phenomenon is seen. Surrounding tissue shows neutrophilic infiltrate with Hematoxylin Eosin stain (H&E, 10x).
The surrounding tissue showed dense neutrophilic infiltrate, with proliferating fibroblasts and capillaries. The colonies stained positively with Gram stain (Figure 3) and Periodic Acid Schiff (PAS) stain but stained negative with Gomori’s Methenamine silver stain (GMS). A diagnosis of actinomycetoma was made in these cases.
Figure 3. Gram stain positive organisms (Gram stain, 40x).
A 43-year-old female with a small swelling over the dorsum of the right foot for ten years and clinically suspected to be ganglion. The swelling was excised and tissue was sent to the histopathology lab. Sections on H&E staining, showed granulomatous inflammation. The centre of the granulomas showed conspicuous dark, thick walled ovoid spores of fungi in clusters (Figure 4). Surrounding tissue showed a dense inflammatory cell infiltrate composed of neutrophils, eosinophils, lymphocytes and numerous multinucleated giant cells. Histopathology with special stains (Gram’s stain, Gomori’s methenamine silver stain, PAS stain) was used to differentiate the organisms. This case was confirmed to be a Eumycetoma.
Figure 4. A colony of the organisms on hematoxylin and eosin staining (H&E, 10x).
Mycetoma is characterized by the formation of grains containing aggregates of the causative organisms that may be discharged onto the skin surface through multiple sinuses. The two main forms are Eumycetoma and Actinomycetoma.
Actinomycetoma is caused by filamentous bacteria such as Actinomadura madurae,Nocardia spp, Streptomyces somaliensis and Actinomadura pelletieri. Actinomycosis mainly manifests as cervicofacial, thoracic and intestinal actinomycosis. On histopathology, an inflammatory reaction is seen with polymorphs, granulation tissue and fibrosis. The organisms form grains, commonly termed as sulphur granules. The bacilli within are 1 micrometre in diameter. A Splendore Hoeppli reaction may be seen peripheral to the bacteria in the grain. [2,5]
Eumycetoma is caused by fungi such as Madurella spp, Curvularia spp, Exophiala jeanselmei, Phialophora verrucosa, Pseudallescheria boydii, Acremonium spp, Aspergillus spp and Fusarium spp. Eumycetoma is a persistent, relentlessly progressive infection, without a tendency to spread systemically. Histopathology shows extensive granulation tissue containing abscesses. The diagnosis can be established by finding sulphur granules, which measure 0.5 mm to 2 mm in diameter and are visible macroscopically.[2,5]
The granules in eumycetoma have septate hyphae which measure 4-5 micron in diameter whereas the granules of actinomycetoma consist of thin, branching filaments measuring 1 micron in diameter. The granules of both actinomycetoma and eumycetoma stain with PAS. However, filaments of actinomycetoma are gram positive whereas those of eumycetoma are gram negative, which help in distinguishing between the two.[2,5]
Cases 1, 2 and 3 were clinically diagnosed as Madura foot. On histological examination, they were diagnosed as actinomycosis. Case 4 was clinically suspected to be ganglion of the foot, but was histologically diagnosed as eumycetoma. Therefore, histological diagnosis was useful in distinguishing between bacterial and fungal infections which can then be treated accordingly. The infection of the forefoot is quite typical in Madura foot. It progresses slowly affecting the deep dermis and subcutaneous tissues and extending to the underlying bones. If it is not diagnosed early enough, mycetoma can cause functional and aesthetic impairments.[4,6]
Since both groups have similar clinical presentation it is important to differentiate between them as the treatment differs. This emphasizes the need for correct diagnosis after meticulous clinical examination, assisted by histopathology, along with the use of special stains.
Athulya Krishna Kumar K T, MBBS
Prema Saldanha, MD, DNBE
Professor, Department of Pathology,
Yenepoya Medical College, Mangalore,
Karnataka 575018, India,
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