Cryptococcosis: Information & Cryptococcosis Specialists

Cryptococcosis is a severe fungal infection of the lungs. If not treated promptly, it has a poor prognosis and is often fatal.

Cryptococcosis was first described in 1894 by

• Otto Busse, a German pathologist from Brandenburg, and
• Abraham Buschke, a German dermatologist,

. In the past, cryptococcosis was also known as “European blastomycosis.”

Cryptococcosis is most commonly caused by the fungus Cryptococcus neoformans. It belongs to the group of so-called encapsulated yeasts and requires a weakened immune system or other underlying medical conditions to cause infection. It is referred to as a facultative pathogen.

In healthy people with a functioning immune system, cryptococcosis usually causes little harm. The body is generally able to fight off the fungal pathogens effectively.

In people infected with HIV, however, the pathogen can multiply rapidly. Cryptococcosis can then spread to other organs. The central nervous system is particularly affected by cryptococcosis in people with HIV.

There is no mandatory reporting requirement for fungal infections, including cryptococcosis. However, it is encouraged to report cases of the disease to the Robert Koch Institute.

Cryptococcosis occurs worldwide. However, it is significantly more common in the United States and Southeast Asia than in Europe.

The mortality rate among HIV patients is approximately 20 percent. In total, over 600,000 people die from cryptococcosis each year.

Nearly one million people living with HIV develop cryptococcal meningoencephalitis—a condition caused by cryptococcosis—each year. Meningoencephalitis is an inflammation of the brain and the meninges.

Animals can also contract cryptococcosis, including cats. In animals, however, the disease affects the lungs, nervous system, and skin to a lesser extent. Instead,

• an infection of the upper respiratory tract,
• discharge from the mouth and eyes, and
• the formation of granulation tissue in the paranasal sinuses.

In addition, tumor-like growths may appear on the face and skull bones. As a result, cryptococcosis is also life-threatening for pets.

In Europe, cryptococcosis is usually caused by the yeast fungus Cryptococcus neoformans. Much less commonly, the pathogen Cryptococcus gattii causes cryptococcosis. This fungus is a variant of Cryptococcus neoformans.

There are 30 other subspecies in the Cryptococcus genus. However, only a few of them appear to be capable of causing cryptococcosis.

It usually takes several weeks from the time of infection until the onset of cryptococcosis.

Cryptococcus neoformans as the causative agent

Cryptococcus neoformans reproduces by budding. This means that a daughter cell, approximately 2 to 8 µm in size, grows out of the mother cell. This yeast belongs to the Basidiomycota phylum. Baker’s yeast, which is also a yeast, belongs to the Ascomycota, however.

Cryptococcus neoformans is most commonly found in soil and on grass and grain stalks. It is also present in bird droppings. When these droppings break down into dust, the pathogen is released into the air, where a host can inhale it. The fungus is highly resistant to heat and desiccation.

Cryptococcus neoformans is so dangerous because it has developed strategies to evade our immune system. The fungus is surrounded by a polysaccharide capsule. This prevents the immune system’s phagocytes from engulfing the fungus and thereby destroying it. In addition, the fungus has incorporated melanin into its cell walls. This, too, makes it resistant to the immune system’s defense cells.

Due to the pathogen’s resilience, it can often cause cryptococcosis.

Routes of Transmission of the Pathogen

Cryptococcus neoformans can multiply very easily in the intestines of birds. Humans inhale the pathogen when bird droppings are stirred up. This allows the pathogen to enter the respiratory tract and the lungs, where cryptococcosis then develops. 

Bird droppings often contain the fungal pathogen Cryptococcus neoformans © Nutlegal | AdobeStock

In very rare cases, transmission via the bloodstream following an injury is also possible. Human-to-human transmission is virtually impossible. Pets, especially cats, can also be affected by cryptococcosis. However, transmission from animals to humans has never been observed to date.

From the lungs, the pathogens travel through the bloodstream to other organs. This is referred to as hematogenous spread. For people with weakened immune systems, the infection can be life-threatening. This includes, among others,

• people infected with HIV,
• people with leukemia,
• people with Hodgkin’s disease, or
• patients who must take corticosteroids.

Fatal lesions can occur, particularly in the brain. Cryptococcosis often leads to the formation of harmful granulomas. The result is life-threatening meningoencephalitis.

The symptoms are often nonspecific. Cryptococcosis frequently causes

• uncharacteristic headaches,
• fever,
• altered consciousness,
• difficulty walking, and
• hearing and vision problems.

Due to the hematogenous spread of the pathogen, impairments can occur almost anywhere in the body:

• in the brain,
• in the eyes,
• the ears,
• in the bones, and
• in the joints.

There is a risk

• of meningoencephalitis (inflammation of the brain and meninges) or
• chronic meningitis (inflammation of the meninges).

Non-specific skin lesions also very commonly occur as a manifestation of cryptococcosis. If cryptococcosis is caused by a skin injury, the infection may remain localized.

Diagnosis begins with a patient interview, the medical history. During this process, the doctor reconstructs the course of a possible infection. This is followed by a physical examination. This includes

• palpation (feeling for abnormalities) and
• auscultation (listening).

If cryptococcosis is suspected, the lungs and the central nervous system are thoroughly examined. Standard imaging techniques are used for this, such as

• funduscopy (examination of the back of the eye) and
• an MRI (magnetic resonance imaging).

Afterward, a lumbar puncture is the most important diagnostic procedure for detecting cryptococcosis. This involves the collection of cerebrospinal fluid (CSF) from the spinal canal and its subsequent examination. A negative stain is applied using an ink preparation.

In the vast majority of cases, analysis of the cerebrospinal fluid can confirm a diagnosis of cryptococcosis.

If only a localized area of the skin is affected, the investigation is initially limited to a biopsy in order to definitively diagnose cryptococcosis.

Since cryptococcosis can be fatal, prompt treatment is lifesaving. Treatment takes place on an inpatient basis, i.e., in a hospital.

Treatment for cryptococcosis depends primarily on the symptoms and the site of the disease. Antimycotics (antifungal medications) are the primary treatment.

If meningitis has already developed, a combination of several antifungal medications is usually necessary. In most cases, the patient is prescribed the antifungal medication

• fluconazole,
• flucytosine, and
• amphotericin B.

The success of the treatment is monitored clinically and through regular lumbar punctures. During a lumbar puncture, cerebrospinal fluid is collected for analysis. If the cerebrospinal fluid is free of pathogens after at least one month, the patient can be switched to secondary prophylaxis.

Cryptococcosis can increase intracranial pressure. In this case, a shunt is necessary.

The goal of treatment is to restore adequate immune function. Once this is achieved, the patient can discontinue treatment—no sooner than six months later.

People with AIDS are typically prescribed the medication fluconazole. It serves as long-term prophylaxis against cryptococcosis.

Otherwise, it is nearly impossible to protect oneself against the disease, as the fungal pathogens are present in the air. Birds, whose droppings often contain fungal pathogens, are found everywhere. If there is a pigeon infestation, it can be controlled to help prevent cryptococcosis.

People with weakened immune systems should strengthen their immune systems through

• regular exercise and
• a balanced, healthy diet

.