Cryptococcosis

Cryptococcosis is a potentially fatal fungal infection of mainly the lungs, presenting as a pneumonia, and in the brain, where it appears as a meningitis.^[4][9][12] Coughing, difficulty breathing, chest pain and fever are seen when the lungs are infected.^[5] When the brain is infected, symptoms include headache, fever, neck pain, nausea and vomiting, light sensitivity and confusion or changes in behavior.^[5] It can also affect other parts of the body including skin, where it may appear as several fluid-filled nodules with dead tissue.^[6]

It is caused by the fungi Cryptococcus neoformans or less commonly Cryptococcus gattii, and is acquired by breathing in the spores from the air.^[4] These fungi are found globally in soil, decaying wood, pigeon droppings, and in the hollows of some species of trees.^[9][13] Whereas C. neoformans generally infects people with HIV/AIDS and those on immunosuppressant drugs and does not usually affect fit and healthy people, C. gattii (found in some parts of Canada and the US) does.^[9][13] Once breathed in, the dried yeast cells colonize the lungs, where they are either cleared by immune cells, lie dormant, or cause infection and spread.^[14]

Diagnosis is by isolating Cryptococcus from a sample of affected tissue or direct observation of the fungus by using staining of body fluids.^[9] It can be cultured from a cerebrospinal fluid, sputum, and skin biopsy.^[9] Characteristic neuroimaging findings include dilated Virchow-Robin spaces, the ‘dirty CSF sign’,^[15] hydrocephalus, cryptococcomas and hazy brain base sign. Many of these findings are non-specific, but the presence of basal meningeal enhancement is significant as it is associated with the future development of cerebral infarct. Treatment is with fluconazole or amphotericin B.^[9][10]

Data from 2009 estimated that of the almost one million cases of cryptococcal meningitis that occurred worldwide annually, 700,000 occurred in sub-Saharan Africa, and 600,000 per year died.^[16] Cryptococcosis was rare before the 1970s, which saw an increase in at-risk groups such as people with organ transplant or on immunosuppressant medications.^[9] The number of cases escalated in the mid-1980s with over 80% occurring in people with HIV/AIDS.^[9] Pigeon breeders (or otherwise people who spend significant time with pigeons) are known to have a high incidence of cryptococcal infections including primary cutaneous cryptococcus due to the fungi's association with pigeon droppings.^[17]