Mycetoma Diagnosis and Causative Agents
Mycetoma
Sample for mycetoma
- Get a sample from the lesion.
- Can take a biopsy of the lesion.
Definition of Mycetoma
- Mycetoma literally means fungal growth or maduromycosis of the foot.
- Mycetoma term refers to severe, deeply chronic, locally progressive, destructive, suppurative, and granulomatous disease.
- It begins in the subcutaneous tissue, usually of the hand and foot.
- This involves subcutaneous tissue, fascia, and bone.
- It is characterized by tumefaction, draining sinuses, and the presence of granules.
Pathology of Mycetoma
- Two types of microorganisms cause Mycetoma:
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Bacteria:
- These are aerobic actinomycetes, which cause Mycetoma called Actinomycetoma in more than 50% of cases.
- The organism in this group are:
- Nocardia brasiliensis.
- Actinomadura pelletieri.
- Actinomadura madurae.
- Streptomyces somaliensis.
- Actinomyces are:
- Actinomyces israelli. It produces actinomycosis.
- This chronic internal abscess formation will develop the sinus tract to the skin.
- There is purulent exudate containing yellow granules called sulfur granules.
- These sulfur granules are masses of actinomycetes.
- Actinomyces bovis.
- Actinomyces israelli. It produces actinomycosis.
-
Fungal:
- Fungal infection causes in the other 50% of the cases.
- This is called Eumycetoma, also known as maduromycosis, and is caused by a true fungus.
- There are at least 23 types of filamentous fungi that cause Mycetoma. An important one is:
- Pseudallescheria boydii (There are yellow granules).
- Madurella mycetomatis (There are big black granules).
- Medurella grisea.
- There are at least 23 types of filamentous fungi that cause Mycetoma. An important one is:
Presentation of mycetoma:
- Mostly there is the involvement of the feet and less common hands and other sites.
- This chronic, suppurative, granulomatous inflammation can involve subcutaneous tissue, fascia, and bone.
- The etiological agents enter the body through the foot from the soil, possibly due to trauma.
- When there is the involvement of the foot, where it is swollen and discolored, numerous draining sinuses form.
- This disease is characterized by tumor formation and draining of the abscess.
- There is the presence of granules or grains in the pus.
- Depending upon the causative agents, these granules have different colors, white, black, yellow, and brown.
- Mycotic mycetoma is more common in men than in women.
- Mycotic mycetoma is usually due to an injury to the foot.
Pathogenesis of mycetoma due to fungi:
- When fungi are implanted in the subcutaneous tissue following the trauma.
- There is a destructive granulomatous lesion that drains through multiple sites.
- There is local spread but no dissemination.
- The most common site is the foot, and this infection is called the Medura foot.
- Causative agent:
- Important fungi are filamentous, including:
- Medurella mycetomatis.
- Medurella grisea.
- Phialophora verrucosa.
- Important fungi are filamentous, including:
- Pathogenesis of fungal Myecetoma:
- First, fungi are implanted into the tissue after trauma, which may be splinter.
- It produces destructive granulomatous inflammation.
- Later on, this lesion drains through multiple sinus tracts.
- There is local spread but no widespread dissemination.
- This is common in barefoot people.
Laboratory Diagnosis of mycetoma:
- Collect the granules from the lesion.
- Then wash the granules with the saline, crush it, and spread it on the slide.
- Also, take the culture of the material. Culture is done on the Sabouraud’s medium for fungus.
- Prepared slides are stained with Gram’s stain :
- The filaments are less than or equal to 1.0 micrometer in diameter; these are diagnostic of aerobic actinomycetes and called actinomycetoma.
- If the filaments are 2 to 5 micrometers and hyphal in shape, is diagnostic of fungal infection is called eumycetoma.
- These granules can also be seen in KOH 10% solution.
Treatment of mycetoma:
- The prognosis of Eumycetoma is poor.
- These patients undergo surgical debridement, oral Itraconazole 200 mg twice a day for a prolonged period of time, and response is only 70%.
- These patients may be given combination therapy.
- Mostly these are treated by surgery.
- Chemotherapy is not effective and is given for a prolonged period of time.
- Treatment surgical and chemotherapy are ineffective when the mycetoma is due to fungi.