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Cryptococcosis, also known as cryptococcal disease, is a potentially fatal fungal disease. It is caused by one of two species; ''Cryptococcus neoformans'' and ''Cryptococcus gattii''. These were all previously thought to be subspecies of ''C. neoformans'' but have now been identified as distinct species. Cryptococcosis is believed to be acquired by inhalation of the infectious propagule from the environment. Although the exact nature of the infectious propagule is unknown, the leading hypothesis is the basidiospore created through sexual or asexual reproduction. == Cause == Cryptococcosis is a defining opportunistic infection for AIDS, and is the second-most-common AIDS-defining illness in Africa. Other conditions that pose an increased risk include certain lymphomas (e.g., Hodgkin's lymphoma), sarcoidosis, liver cirrhosis, and patients on long-term corticosteroid therapy. Distribution is worldwide in soil. The prevalence of cryptococcosis has been increasing over the past 20 years for many reasons, including the increase in incidence of AIDS and the expanded use of immunosuppressive drugs. In humans, ''C. neoformans'' causes three types of infections: * Wound or cutaneous cryptococcosis * Pulmonary cryptococcosis * Cryptococcal meningitis. Cryptococcal meningitis (infection of the meninges, the tissue covering the brain) is believed to result from dissemination of the fungus from either an observed or unappreciated pulmonary infection. Often there is also silent dissemination throughout the brain when meningitis is present. ''Cryptococcus gattii'' causes infections in immunocompetent people (fully functioning immune system), but ''C. neoformans v. grubii'', and ''v. neoformans'' usually only cause clinically evident infections in persons with some form of defect in their immune systems (immunocompromised persons). People with defects in their cell-mediated immunity, for example, people with AIDS, are especially susceptible to disseminated cryptococcosis. Cryptococcosis is often fatal, even if treated. It is estimated that the three-month case-fatality rate is 9% in high-income regions, 55% in low/middle-income regions, and 70% in sub-Saharan Africa. As of 2009 there were globally approximately 958,000 annual cases and 625,000 deaths within three months after infection. Although the most common presentation of cryptococcosis is of ''C. neoformans'' infection in an immunocompromised person (such as persons living with AIDS), the ''C. gattii'' is being increasingly recognised as a pathogen in what is presumed to be immunocompetent hosts,〔Tripathi K, Mor V, Bairwa NK, Del Poeta M, Mohanty BK. (2012).("Hydroxyurea treatment inhibits proliferation of Cryptococcus neoformans in mice." )〕 especially in Canada and Australia. This may be due to rare exposure and high pathogenicity, or to unrecognised isolated defects in immunity, specific for this organism. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cryptococcosis」の詳細全文を読む スポンサード リンク
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