Cryptococcal Meningitis

Cryptococcal meningitis is typically caused by the fungus Cryptococcus neoformans.

Infection begins when aerosolized desiccated yeast cells or spores are inhaled from environmental sources, such as aged pigeon droppings.

The spores survive in the lung alveoli, where they can remain extracellular or be phagocytosed by alveolar macrophages.

Here, the spores enlarge and germinate into the fungal form, which expresses two major virulence factors: a capsule that promotes immune evasion, and melanin, which protects against oxidative stress.

Melanin also binds to antifungal agents, reducing the pathogen’s susceptibility to drugs.

The fungus multiplies inside macrophages, exits the cells, and spreads through the bloodstream to the central nervous system.

Here, it produces enzymes like metalloproteinases that help cross the blood–brain barrier.

The fungus enters and multiplies in the cerebrospinal fluid.

This results in inflammation of the meninges and obstruction of CSF outflow, leading to an increase in intracranial pressure.

As a result, patients experience persistent headache, fever, and visual disturbances.