Mycetoma

Mycetoma is a chronic subcutaneous infection caused by actinomycetes or fungi. This infection results in a granulomatous inflammatory response in the deep dermis and subcutaneous tissue, which can extend to the underlying bone. 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. Mycetoma named because of the tumour-like mass it forms.

More than 20 species of fungi and bacteria can cause mycetoma. The ratio of mycetoma cases caused by bacteria (actinomycetoma) to those caused by true fungi (eumycetoma) is 197:67.

History

Mycetoma was described first in the mid-1800s and was initially called Madura foot. Mycetoma (a tumor produced by fungi) was first described in 1842 in the Madura district of India, hence the terms “Madura foot,” “maduromycosis,” and “maduromycetoma.” Mycetoma is a chronic, slowly progressive infection of diverse etiology that starts in subcutaneous tissue and spreads across tissue planes to contiguous structures. 

Infectious agents

Two groups of soil-inhabiting pathogens, each of which accounts for approximately 50% of cases, cause mycetoma: (1) filamentous aerobic actinomycetes, hence the termactinomycetoma, and (2) a wide range of saprophytic soil and woody plant fungi, hence the termeumycetoma.

·         Even more numerous are the agents that cause eumycetoma, such as Madurella species, probably the most prevalent mycetoma-causing fungal species worldwide (e.g., Madurella mycetomatis causes 70% of all cases of eumycetoma), as well as Fusarium species, Acremonium species, Pseudallescheria boydii, Exophialaspecies, and Curvularia species.

A variety of Nocardia species (e.g., Nocardia brasiliensis, Nocardia asteroides), Actinomaduraspecies (e.g., Actinomadura pelletieri, Actinomadura madurae), and Streptomyces species (e.g.,Streptomyces somaliensis) have been reported to cause actinomycetoma.

Site of infection      

Infection enters through sites of local trauma, eg cut or splinter, causing a granulomatous reaction. Spread occurs through skin facial planes and can involve the bone. It most commonly involves the foot but can involve the hands, back or shoulders.

Signs & symptoms 

• The earliest sign of mycetoma is a painless subcutaneous swelling. Some patients have a history of a penetrating injury at that site.
• Slow spreading skin infection
• Local swelling
• Pus on skin
• Small hard painless nodules
• Ulceration
• Pus discharge
• Holes in skin
• Scarred skin
• Pale skin
• Itching
• Pain
• Burning sensation

 Complications

• Muscle complications
• Muscle infection
• Bone complications
• Bone infection
• Amputation - in severe cases
• Secondary bacterial infection
• Deformity (type of Orthopedic disorders)

Epidemiology  

Although mycetoma has a broad worldwide distribution, it occurs primarily in the tropical and, to a lesser extent, the temperate zones. More specifically, the infection is quite prevalent in India, Mexico, Central America, South America, the Middle East, and especially sub-Saharan Africa (the “mycetoma belt”); Sudan in particular has a high burden of mycetoma. Indigenously acquired mycetoma is sporadic in North America and Europe. However, the globalization of tourism and the increase in immigration from countries with a high endemicity of mycetoma to Western countries necessitates awareness of this entity, even in the developed world.

• There are a series of case reports from African countries including Sudan.
• The incidence of mycetoma is likely to rise in temperate regions due to increases in worldwide travel and, since mycoses are not notifiable, the incidence in the UK is unknown.

Diagnosis  

·         The causative organisms can be detected by examining surgical tissue biopsy as well the lesion sinuses discharge.

·         Grains microscopy is helpful in detecting the characteristic grains, it is important to culture them to identify the causative organism properly.

·         Other useful techniques for the diagnosis of mycetoma and that included DNA sequencing and many imaging techniques.

 All these tests are not commonly available in endemic areas. There are no simple friendly used diagnostic tests to use in mycetoma endemic villages.

The specific manifestations of mycetoma are sometimes confused with those of other rare entities. For example, mycetoma must occasionally be distinguished from chronic cutaneous fungal infections such as sporotrichosis (mycetomatous lymphatic sporotrichosis) and dermatophytic mycetoma. The latter infection, which is typically seen in Africans and sometimes called pseudomycetoma, is a painless granulomatous induration of the skin and subcutaneous tissues caused by ringworm that may be associated with grains consisting of fungi. 

Treatment

The treatment depends on the causative organisms for the bacterial; it is a long term antibiotics combination whereas for fungal type it is combined antifungals drugs and surgery. The treatment is unsatisfactory, has many side effects, expensive and not available in endemic areas.

If left untreated, mycetoma can affect the underlying bones, joints, or adjacent organs.

Risk factors

• Mycetoma typically presents in agricultural workers (hands, shoulders and back - from carrying contaminated vegetation and other burdens), or in individuals who walk barefoot in dry, dusty conditions.
• Minor trauma allows pathogens from the soil to enter the skin.

Prevention & Control

Mycetoma is not a notifiable disease (a disease required by law to be reported) and no surveillance systems exist. There no preventable or control programmes for mycetoma yet. Preventing infection is difficult, but people living in or travelling to endemic areas should be advised not to walk barefooted.