Studying the Tissue Microenvironment Signatures of the Mycetoma Granuloma

Mycetoma is a chronic, specific, subcutaneous granulomatous, progressive and disfiguring inflammatory disease. It is caused by true fungi or by certain bacteria and hence it is usually classified into eumycetoma and actinomycetoma respectively. Madurella mycetomatis is the commonest eumycetoma causative agent, while Streptomyces somaliensis and Nocardia brasiliensis are the common causative organisms for actinomycetoma. The triad of a painless subcutaneous mass, sinuses formation and purulent or sero-purulent discharge that contains grains is pathognomonic of mycetoma. The inflammatory subcutaneous granuloma usually spreads to involve the skin and the deep structures, resulting in destruction, deformity and loss of function, occasionally it can be fatal. The foot and hand are the most frequently affected sites seen in 82% of cases. In endemic areas, other parts of the body may be involved such as the knee, arm, leg, head and neck, thigh and perineum. No age is exempted in mycetoma; however, it occurs more frequently in young adult men in the age range 20-40 years and almost 30% of reported patients were young students.

The true incidence and prevalence of mycetoma world-wide is not precisely known. It is interesting to note that most of the reported mycetoma data are related to hospital patients with advanced disease. This is attributed to the nature of mycetoma which is usually painless, slowly progressive and the late presentation of the majority of patients due to the poor health education, lack of health facilities and financial constraints.

The worldwide distribution of mycetoma varies widely. It is endemic in many tropical and subtropical regions and prevails in the mycetoma belt, which includes the countries of Sudan, Somalia, Senegal, India, Yemen, Mexico, Venezuela, Columbia, Argentina, and a few others. The African continent seems to have the highest burden and prevalence of the disease. It has also been extensively reported from India. However, mycetoma has been reported in many temperate regions as well. There are a few reports on mycetoma from the USA, Sri Lanka, Germany, Egypt, Turkey, Philippines, Japan, Lebanon, Thailand, Saudi Arabia, Tunisia and Iran.

The proper treatment of mycetoma depends mainly on accurate diagnosis. It is essential to identify the causative organism to the species level and the current tests for that are the classical grains culture, surgical biopsy histopathological examination and various molecular techniques such as PCR. Various imaging techniques such as conventional radiology, ultrasonography, CT scan and MRI are in use to determine the disease extend. Most of these tests and techniques are invasive, expensive and of low sensitivity and specificity. Furthermore, they are not available in the mycetoma endemic regions and hence there is a desperate need forth easy to use, field-friendly test to identify the causative agent.

The management of this distressing and devastating disease is disappointing. The treatment depends mainly on the aetiological agent, the site and extend of the disease. Until recently, the only available treatment for mycetoma was amputation or multiple mutilating disfiguring surgical excisions. Combined medical treatment in the form of antifungals for the eumycetoma and antibiotics and antimicrobial agents for actinomycetoma and various surgical excisions is the gold standard in mycetoma.