Mycetoma

Disease name and synonyms

Mycetoma; eumycetoma when caused by fungi, actinomycetoma when caused by bacteria.

Fungi responsible

The most common fungal causative agents are Madurella mycetomatis, Madurella tropicana, Madurella fahali and Scedosporium apiospermum.

Disease description

The disease is characterised by a painless subcutaneous mass, multiple sinuses and purulent or seropurulent discharge containing mycetoma grains.  Grains are of various colours, sizes and consistent with the causative organism. The subcutaneous mass usually spreads to involve the skin and deep structures, resulting in destruction, deformity and loss of function – occasionally it can be fatal.

In more than 80% of patients mycetoma affects the hand or foot. Occasional cases of head and neck, chest, abdominal wall, perineum or gluteal region are recorded. Rare mycetoma sites include the eye, sinuses, mastoid bone and scrotum.

Eumycetoma has a slower progression than the more rapidly invasive actinomycetoma, but ultimately can be just as destructive.

Frequency and global burden

The disease is endemic in many tropical and subtropical regions across the world, with high prevalence in the ‘mycetoma belt’. The belt stretches between 150⁰S and 300⁰N, and includes Sudan, Somalia, Senegal, India, Yemen, Mexico, Venezuela, Columbia, Argentina, and Iran, amongst others. There are probably between 20,000 and 50,000 cases worldwide based on literature reports. Most cases are reported from Sudan, Mexico and India..

Underlying problems and at risk patients

The most common age of infection is young adulthood (70% of the cases are between ages 11 and 40), with some children and older people affected. In most countries men are affected more than women.

Diagnostic testing

Surgical biopsy is important to obtain grains for culture, molecular identification and histopathological examination. Individual grains have a distinctive appearance under direct microscopy, depending on causative agent, but this is insufficient to determine the bacteria or fungi responsible for the infection.

Culture requires a range of media, including fungal, bacterial and mycobacteria plates and/or liquid culture. Years of experience are required to identify all of the fungi and bacteria that cause mycetoma, and there are many variants and isolates that resemble others. It is recommended to plate as many grains as possible in order to increase the chance of culturing the organism.

Formal genetic identification using sequencing is most reliable. Susceptibility testing is not standardized and has not been well correlated with treatment outcome. Various imaging modalities are useful to define the extent of disease. Conventional X-ray, ultrasound to identify grains and MRI all have an essential place in determining the disease spread, and to establish a disease management plan. Currently, the available diagnostic tests and techniques are invasive, tedious and expensive. Most of them do not exist in endemic regions, and patients need to travel far to establish the diagnosis.

Treatment

The treatment of eumycetoma involves a combination of antifungal treatment (currently itraconazole 400mg/day) and surgical excision. Excision ranges in extent from wide local excision to repetitive debridement, and in severe cases, amputation. Surgery is indicated for cases resistant to medical therapy and when the lesion is localised. It may be life-saving in advanced disease that is complicated by secondary bacterial infection, sepsis, massive bone involvement, and poor general condition. Some data indicate that voriconazole may be a better treatment for certain organisms, notably Medicopsis (Pyrenochaeta) romeroi. Eumycetoma treatment is prolonged with a low cure rate and high recurrence and dropout rates.

Outlook and prognosis

Eumycetoma patients usually respond poorly to medical therapy. Improvement is slow and hard to evaluate, even after months of treatment. Many patients eventually fail to complete education or lose their jobs.

 

 

For more information on actinomycetoma see Dermatology Advisor

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