Cryptococcosis is a condition that is caused by infection with a fungus from the Cryptococcus family. There are over 30 types of this fungus but there are two main species that are responsible for nearly all cryptococcus infections in both humans and animals. These are called Cryptococcus neoformans and Cryptococcus gatti.
Risks and transmission of infection
C. neoformans and C. gatti are very common in the environment, particularly in soil. People are at risk of infection if they inhale airborne spores of these fungus species, although very few people become ill after exposure to the spores. C. neoformans primarily affects people with weakened immunity such as those with HIV or who are taking immunosuppressants.
Symptoms and signs of the infection
In most cases, the spores are inhaled and therefore initially replicate in the lungs. Most individuals with pulmonary infections do not display symptoms even if they are immunocompetent, although an X-ray may reveal lung lesions.
In the minority of cases where symptoms do develop, signs may vary from a non-specific cough to more severe symptoms such as shortness of breath (dyspnea) or pleuritic chest pain. Other symptoms include fever, weight loss, malaise and coughing up blood or hemoptysis. On rare occasions, pleural effusion occurs.
Severe pulmonary diseases and respiratory syndromes are more likely to occur in those with weakened immune systems. In healthy patients, infection may be self-limited. In people with HIV/AIDS, however, the fungus can lie dormant in the body and reactivate at a later point, spreading to other sites in the body and causing serious infections and symptoms.
Diagnosis and treatment
Cryptcoccosis infection is suspected based on symptoms and is confirmed using culturing techniques. This is achieved using a sample of cerbrospinal fluid, sputum or urine. The sample is placed on a glass slide and stained with special dyes which help to detect the fungi when the sample is analysed under the microscope.
Aside from direct conventional methods, some rapid diagnostic tests to detect the cryptococcal antigen include the latex agglutination test, lateral flow immunochromatographic assay (LFA) and enzyme immunoassay (EIA). One new LFA test was approved by the FDA in 2011.
Treatment generally involves the use of typical antifungal agents such as amphotericin B, flucytosine, itraconazole, fluconazole and ketoconazole.
Reviewed by Sally Robertson, BSc