Respiratory and systemic mycoses: an overview

Respiratory and systemic mycoses are globally emerging as a problem of increasing importance in infectious diseases. This is attributed to the growing population of immunocompromised patients due to epidemic outbreak of AIDS or to other factors such as use of immunosuppressive drugs in recipients of organ transplantation. The available evidence has unequivocally established the endemic occurrence of blastomycosis, histoplasmosis and penicilliosis mameffei in India. In fact, pencilliosis marneffei has emerged as a major endemic mycosis of AIDS patients in Southeast Asia. It has manifestations simulating those of histoplasmosis capsulati, and it may spread to other regions with enlarging population of AIDS patients. Comprehensive studies are indicated in order to delineate the endemic areas of the afore-mentioned systemic mycoses. Among the other important systemic mycoses reported from India are aspergillosis, cryptococcosis, candidiasis and zygomycosis. Our current knowledge of the global distribution of systemic mycoses does not depict their true prevalence. It largely reflects the geographic distribution of medical mycologists or other investigators engaged in the study of fungal diseases and their research interests. Invasive aspergillosis has emerged as an important disease in patients with neutropenia and bone narrow transplant recipients, cryptoccosis, penicilliosis marneffei and pneumocystosis in patients with AIDS, fusariosis in patients with leukaemia receiving cytotoxic therapy, zygomycosis in diabetic patients and in patients on defroxamine therapy, and Malasseziafurfur infection in patients on total parenteral nutrition: Opportunistic systemic mycoses due to yeasts and yeast-like fungi have become commoner than those due to filamentous fungi, occupying fourth position in the list of bloodstream pathogens in some centers in USA. Also, their incidence, pattern of clinical presentations and species spectrum have significantly changed, largely due to more frequent and prolonged therapeutic or prophylactic use of antifungal drugs and subsequent development of resistance. Consequently, infections with resistant yeast-like fungi such as C. lusitaniae, C. krusei, C. tropicalis, C. glabrata and Trichosporon ovoides (T. beigelii) have recently been reported with greater frequency. Since respiratory and systemic mycoses have no pathognomonic clinical or radiologic syndrome and mycological diagnostic facilities are restricted to only some of the major metropolitan centres, these diseases may be frequently confused with tuberculosis or other diseases of obscure etiology in India and other developing countries. Greater awareness and a high index of clinical suspicion are important pre-requisites for their diagnosis. Also, active collaboration of internists, pathologists, mycologists and microbiologists is advocated for their expeditous diagnosis and successful management. Further studies should focus on the development of rapid techniques for selective isolation and identification of systemic pathogenic fungi. The problem of antifungal resistance is likely to become more serious in the future as more and more patients with AIDS, bone marrow transplantation and neutropenia will require chemoprophylaxis cover against systemic fungal infections. Thus, it would be of vital importance to intensify search for more potent and less toxic antifungal drugs. It is recognized that an increasing number of people whose life is saved or prolonged due to successful treatment of their underlying diseases fall victim to opportunistic, life threatening systemic mycoses. A great majority of the deaths due to these infections occurs because they remain undiagnosed for want of mycological diagnostic services. In order to cope with the challenge of systemic mycoses, the health authorities of the developing countries are called upon to urgently take necessary measures for establishing a network of diagnostic mycology laboratories.