Cryptococcosis is a potentially fatal

fungal infection Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ti ...

of mainly the

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

, presenting as a

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

, and

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

, where it appears as a

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...

Cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three pha ...

difficulty breathing Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing disc ...

chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with n ...

and

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

are seen when the lungs are infected. When the brain is infected, symptoms include

headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...

, fever,

neck pain Neck pain, also known as cervicalgia, is a common problem, with two-thirds of the population having neck pain at some point in their lives. Neck pain, although felt in the neck, can be caused by numerous other spinal problems. Neck pain may arise ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

and

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...

light sensitivity Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity ...

and

confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"

or changes in behaviour. It can also affect other parts of the body including

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, where it may appear as several fluid-filled nodules with

dead tissue Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated diges ...

. It is caused by the

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

Cryptococcus neoformans ''Cryptococcus neoformans'' is an encapsulated yeast belonging to the class Tremellomycetes and an obligate aerobe that can live in both plants and animals. Its teleomorph is a filamentous fungus, formerly referred to ''Filobasidiella neoformans' ...

'' or less commonly ''

Cryptococcus gattii ''Cryptococcus gattii'', formerly known as ''Cryptococcus neoformans'' var. ''gattii'', is an encapsulated yeast found primarily in tropical and subtropical climates. Its teleomorph is ''Filobasidiella bacillispora'', a filamentous fungus belongi ...

'', and is acquired by breathing in the

spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

from the air. These fungi are found around the world in soil, decaying wood, pigeon droppings, and in the hollows of some species of trees. Whereas ''C. neoformans'' infects generally people with HIV/AIDS and those on

immunosuppressant drugs Immunosuppressive drugs, also known as immunosuppressive agents, immunosuppressants and antirejection medications, are drugs that inhibit or prevent activity of the immune system. Classification Immunosuppressive drugs can be classified into ...

and does not usually affect fit and healthy people, ''C. gattii'' (found in some parts of Canada and the US) does. Once breathed in, the dried yeast cells colonize the lungs, where they are either cleared by

immune cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

, lie dormant, or cause infection and spread. Diagnosis is by isolating Cryptococcus from a sample of affected tissue or direct observation of the fungus by using staining of body fluids. It can be cultured from a

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

, sputum, and

skin biopsy Skin biopsy is a biopsy technique in which a skin lesion is removed to be sent to a pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 days. ...

. Treatment is with

fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prevent ...

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. Fo ...

. 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. Cryptococcosis was rare before the 1970s which saw an increase in at-risk groups such as people with

organ transplant Organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organs may be transpo ...

or on immunosuppressant medications. The number of cases escalated in the mid-1980s with over 80% occurring in people with

HIV/AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual ...

. Pigeon breeders (or otherwise people who spend significant time with pigeons, known as “pigeon fanciers”) are known to have a high incidence of cryptococcal infections including PCC due to Cryptococcus' association with pigeon droppings.

Classification

Cryptococcus is generally classified according to how it is acquired and its site. It typically begins in the lungs before spreading to other parts of the body, particularly the brain and nervous system. The skin type is less common.

Signs and symptoms

Cough, shortness of breath, chest pain and fever are seen when the lungs are infected, appearing like a pneumonia. There may also be feeling of tiredness. When the brain is infected, symptoms include headache, fever, neck pain, nausea and vomiting, light sensitivity, confusion or changes in behaviour. It can also affect other parts of the body including skin, eyes, bones and prostate. In the skin, it may appear as several fluid-filled nodules with

. Depending on the site of infection, other features may include

loss of vision Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

blurred vision Blurred vision is an ocular symptom where vision becomes less precise and there is added difficulty to resolve fine details. Temporary blurred vision may involve dry eyes, eye infections, alcohol poisoning, hypoglycemia, or low blood pressure. ...

, inability to move an eye and memory loss. Symptom onset is often sudden when lungs are infected and gradual over several weeks when the central nervous system is affected.

Cause

Cryptococcosis is a common opportunistic infection for

AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...

, and is particularly common among people living with AIDS in

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. Other conditions that pose an increased risk include certain

malignancies Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

(such as

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...

), liver

cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue repai ...

s, and long-term

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...

therapy. Distribution is worldwide in soil. The prevalence of cryptococcosis has been increasing over the past 50 years for many reasons, including the increase in incidence of AIDS and the expanded use of immunosuppressive drugs. In humans, ''C. neoformans'' chiefly infects the skin, lungs, and central nervous system (causing

). Less commonly it may affect other organs such as the eye or prostate.

Primary Cutaneous Cryptococcosis

Primary Cutaneous Cryptococcosis (PCC) is a distinct clinical diagnosis separate from the secondary cutaneous cryptococcosis that is spread from systematic infection. Males are more likely to develop the infection and a 2020 study showed that the sex bias may be due to a growth hormone, produced by ''C. neoformans'' called gibberellic acid (GA) that is upregulated by testosterone. The upper limbs account for a majority of infections. Isolates found in PCC include ''

'' (most common), ''

'', and ''

Cryptococcus laurentii ''Papiliotrema laurentii'' (synonym ''Cryptococcus laurentii'') is a species of fungus in the family Rhynchogastremaceae. It is typically isolated in its yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of th ...

''. Prognosis for PCC is generally good outside of disseminated infection. Morphologic description of the lesions show umbilicated papules, nodules, and violaceous plaques that can mimic other cutaneous diseases like

molluscum contagiosum Molluscum contagiosum (MC), sometimes called water warts, is a viral infection of the skin that results in small raised pink lesions with a dimple in the center. They may become itchy or sore, and occur singularly or in groups. Any area of the sk ...

and

Kaposi's sarcoma Kaposi's sarcoma (KS) is a type of cancer that can form masses in the skin, in lymph nodes, in the mouth, or in other organs. The skin lesions are usually painless, purple and may be flat or raised. Lesions can occur singly, multiply in a limite ...

. These lesions may be present months before other signs of system infection in patients with AIDS.

Pulmonary Cryptococcosis

Cryptococcus (both ''C. neoformans'' and ''C. gattii'') plays a common role in pulmonary invasive mycosis seen in adults with HIV and other immunocompromised conditions.Setianingrum F, Rautemaa-Richardson R, Denning DW. Pulmonary cryptococcosis: A review of pathobiology and clinical aspects. Med Mycol. 2019 Feb 1;57(2):133-150. doi: 10.1093/mmy/myy086. PMID 30329097. It also affects healthy adults at a much lower frequency and severity as healthy hosts may have no or mild symptoms. Immune-competent hosts may not seek or require treatment, but careful observation may be important. Cryptococcal pneumonia has a potential to disseminate to the central nervous system (CNS) especially in immunocompromised individuals. Pulmonary cryptococcosis has a worldwide distribution and is commonly underdiagnosed due to limitations in diagnostic capabilities. Since pulmonary nodules are its most common radiological feature, it can clinically and radiologically mimic lung cancer, TB, and other pulmonary mycoses. The sensitivity of cultures and the Cryptococcal (CrAg) antigen with lateral flow device on serum are rarely positive in the absence of disseminated disease. Moreover, pulmonary cryptococcosis worsen the prognosis of cryptococcal meningitis.

Cryptococcal meningitis

Cryptococcal meningitis (infection of the

meninges In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in th ...

, 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. People with defects in their

cell-mediated immunity Cell-mediated immunity or cellular immunity is an immune response that does not involve antibodies. Rather, cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in ...

, for example, people with

, are especially susceptible to disseminated cryptococcosis. Cryptococcosis is often fatal, even if treated. It is estimated that the three-month

case-fatality rate In epidemiology, case fatality rate (CFR) – or sometimes more accurately case-fatality risk – is the proportion of people Medical diagnosis, diagnosed with a certain disease, who end up Cause of death, dying of it. Unlike a disease's mortalit ...

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 ''C. neoformans'' infection most commonly occurs as an opportunistic infection in immunocompromised people (such as those living with AIDS), ''C. gattii'' often infects immunocompetent people as well.

Cryptococcus ''Cryptococcus'' is a genus of fungi in the family Cryptococcaceae that includes both yeasts and filamentous species. The filamentous, sexual forms or teleomorphs were formerly classified in the genus ''Filobasidiella'', while ''Cryptococcus'' ...

(both ''

C. neoformans ''Cryptococcus neoformans'' is an encapsulated yeast belonging to the class (biology), class Tremellomycetes and an obligate aerobe that can live in both plants and animals. Its teleomorph is a filamentous fungus, formerly referred to ''Filobasid ...

'' and '' C. gattii'') is the dominant and leading etiologic agent of meningitis in adults with HIV and is considered an "emerging" disease in healthy adults. Though the rate of infection is clearly higher with immunocompromised individuals, some studies suggest a higher mortality rate in patients with non-HIV cryptococcal meningitis secondary to the role of T-cell mediated reaction and injury. CD4+ T cells have proven roles in the defense against Cryptococcus, but it can also contribute to clinical deterioration due its inflammatory response.

Diagnosis

Dependent on the infectious syndrome, symptoms include fever, fatigue, dry cough, headache, blurred vision, and confusion. Symptom onset is often subacute, progressively worsened over several weeks. The two most common presentations are meningitis (an infection in and around the brain) and pulmonary (lung) infection. Any person who is found to have cryptococcosis at a site outside of the central nervous system (e.g., pulmonary cryptococcosis), a

lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to ...

is indicated to evaluate the

(CSF) for evidence of cryptococcal meningitis, even if they do not have signs or symptoms of CNS disease. Detection of cryptococcal

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

(capsular material) by

culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.Tyl ...

of CSF,

sputum Sputum is mucus that is coughed up from the lower airways (the trachea and bronchi). In medicine, sputum samples are usually used for a naked eye examination, microbiological investigation of respiratory infections and cytological investigations ...

and

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

provides definitive diagnosis. Blood cultures may be positive in heavy infections. India ink of the CSF is a traditional microscopic method of diagnosis, although the sensitivity is poor in early infection, and may miss 15–20% of patients with culture-positive cryptococcal meningitis. Unusual morphological forms are rarely seen. Cryptococcal antigen from

is the best test for diagnosis of cryptococcal meningitis in terms of sensitivity. Apart from conventional methods of detection like direct microscopy and culture, rapid diagnostic methods to detect cryptococcal antigen by latex agglutination test, lateral flow

immunochromatographic Affinity chromatography is a method of separating a biomolecule from a mixture, based on a highly specific macromolecular binding interaction between the biomolecule and another substance. The specific type of binding interaction depends on the ...

assay (LFA), or enzyme immunoassay (EIA). A new cryptococcal antigen LFA was FDA approved in July 2011. Polymerase chain reaction (PCR) has been used on tissue specimens. Cryptococcosis can rarely occur in the non-immunosuppressed people, particularly with ''

''. Image:Cryptococcosis of lung in patient with AIDS. Mucicarmine stain 962 lores.jpg Image:Pulmonary cryptococcosis (1) histiocytic penumonia.jpg Image:Pulmonary cryptococcosis (3) Alcian blue-PAS.jpg Image:Cryptococcus smear MGG 2010-01-26.JPG Image:Cryptococcus smear MGG 2010-01-27.JPG Image:Cryptococcus smear PAS 2010-01-26.JPG

Prevention

Cryptococcosis is a very subacute infection with a prolonged subclinical phase lasting weeks to months in persons with HIV/AIDS before the onset of symptomatic meningitis. In Sub-Saharan Africa, the prevalence rates of detectable cryptococcal antigen in peripheral blood is often 4–12% in persons with CD4 counts lower than 100 cells/mcL. Cryptococcal antigen screen and preemptive treatment with fluconazole is cost saving to the healthcare system by avoiding cryptococcal meningitis. The World Health Organization recommends cryptococcal antigen screening in HIV-infected persons entering care with CD4<100 cells/μL. This undetected subclinical cryptococcal (if not preemptively treated with anti-fungal therapy) will often go on to develop cryptococcal meningitis, despite receiving HIV therapy. Cryptococcosis accounts for 20-25% of the mortality after initiating HIV therapy in Africa. What is effective preemptive treatment is unknown, with the current recommendations on dose and duration based on expert opinion. Screening in the United States is controversial, with official guidelines not recommending screening, despite cost-effectiveness and a 3% U.S. cryptococcal antigen prevalence in CD4<100 cells/μL. Antifungal prophylaxis such as fluconazole and itraconazole reduces the risk of contracting cryptococcosis in those with low CD4 cell count and high risk of developing such disease in a setting of cryptococcal antigen screening tests are not available.

Treatment

Treatment options in persons without HIV-infection have not been well studied.

Intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

Amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. Fo ...

combined with

flucytosine Flucytosine, also known as 5-fluorocytosine (5-FC), is an antifungal medication. It is specifically used, together with amphotericin B, for serious ''Candida'' infections and cryptococcosis. It may be used by itself or with other antifungals for ...

by mouth is recommended for initial treatment (induction therapy). People living with AIDS often have a greater burden of disease and higher mortality (30–70% at 10-weeks), but recommended therapy is with

and

. Where

is not available (many low and middle income countries),

should be used with amphotericin.

Amphotericin Amphotericin B is an antifungal medication used for serious mycosis, fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candida infections, candidiasis, coccidioidomy ...

-based induction therapy has much greater microbiologic activity than

monotherapy with 30% better survival at 10-weeks. Based on a systematic review of existing data, the most cost-effective induction treatment in resource-limited settings appears to be one week of amphotericin B coupled with high-dose

. After initial induction treatment as above, typical consolidation therapy is with oral

for at least 8 weeks used with secondary prophylaxis with fluconazole thereafter. The decision on when to start treatment for HIV appears to be very different than other opportunistic infections. A large multi-site trial supports deferring ART for 4–6 weeks was overall preferable with 15% better 1-year survival than earlier ART initiation at 1–2 weeks after diagnosis. A 2018 Cochrane review also supports the delayed starting of treatment until cryptococcosis starts improving with antifungal treatment.

IRIS

The

immune reconstitution inflammatory syndrome Immune reconstitution inflammatory syndrome (IRIS) is a condition seen in some cases of AIDS or immunosuppression, in which the immune system begins to recover, but then responds to a previously acquired opportunistic infection with an overwhel ...

(IRIS) has been described in those with normal immune function with meningitis caused by ''C. gattii'' and ''C. grubii''. The increasing inflammation can cause brain injury or be fatal.

Epidemiology

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.

Other animals

Cryptococcosis is also seen in cats and occasionally dogs. It is the most common deep fungal disease in cats, usually leading to chronic infection of the nose and sinuses, and skin ulcers. Cats may develop a bump over the bridge of the nose from local tissue inflammation. It can be associated with FeLV infection in cats. Cryptococcosis is most common in dogs and cats but cattle, sheep, goats, horses, wild animals, and birds can also be infected. Soil, fowl manure, and

pigeon Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...

droppings are among the sources of infection.

References

External links

Medscape entry on cryptococcosis
{{Diseases of meninges Animal fungal diseases Bird diseases Bovine diseases Cat diseases Dog diseases Fungi and humans HIV/AIDS Horse diseases Mycosis-related cutaneous conditions Sheep and goat diseases Tremellomycetes Zoonoses Fungal diseases