Cryptococcosis

Epidemiology

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Etiology

• Caused by encapsulated yeast: Cryptococcus neoformans (worldwide, associated with pigeon droppings, immunocompromised hosts) and C. gattii (tropical/subtropical areas, can infect immunocompetent hosts).
• Transmission is via inhalation of spores. The primary infection is in the lungs, often asymptomatic.
• Hematogenous dissemination to the CNS is the most common and feared manifestation, especially in immunocompromised individuals.
• The thick polysaccharide capsule is a major virulence factor, inhibiting phagocytosis.

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Pathophysiology

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Clinical features

• Cryptococcal meningoencephalitis or brain abscess
  • Hematogenous spread of fungi to meninges
  • Headache, fever, signs of increased intracranial pressure, confusion, absent meningeal signs
• Pulmonary cryptococcosis
  • Most commonly seen in immunocompromised patients
  • Clinical presentation is variable and nonspecific (e.g., cough, fever, shortness of breath).

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Diagnostics

• Latex agglutination test: positive for cryptococcal polysaccharide capsular antigen
  • High specificity and sensitivity
  • Specimen: Blood or CSF
• CSF analysis
  • India ink stain: clear halo; Round or oval budding yeast
  • Mucicarmine: stains the thick inner polysaccharide capsule bright red
  • Fungal culture (Sabouraud agar) showing:
    • 5–10 μm yeast
    • Thick polysaccharide capsule
    • Narrow, unequal budding
• MRI: “Soap bubble” lesions in cryptococcal encephalitis

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Treatment

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