Cryptococcosis
Key Facts
Terminology
Lung infection caused by inhalation of Cryptococcus neoformans spores
Clinical Issues
Acute pulmonary infection can be asymptomatic or self-limited
Progressive infection is seen in immunocompromised hosts and involves lungs and meninges
Microscopic Pathology
Nodular granulomatous lesions with multinucleated giant cells containing intracellular organisms
Nodular lesions may progress to form necrotizing granulomas with palisading histiocytes
Multiple organisms can be seen lying free within alveolar spaces with no inflammation in alveolar walls
C. neoformans yeast are small (4-6 µm in diameter), eosinophilic, round to oval, and occasionally appear refractile with single budding
Cells appear to be surrounded by a halo that actually represents a mucinous capsule
Capsule-deficient variant of C. neoformans is found in immunocompromised patients
Ancillary Tests
Organisms stain with silver stains (GMS) and PAS
Capsule of organisms stains strongly with mucicarmine and Alcian blue stains
Capsule-deficient variant of C. neoformans stains with Fontana-Masson stain
 Gross appearance of cryptococcal infection in the lung shows multiple cryptococcomas distributed in the periphery of the upper lobe. |
 Histologic appearance of cryptococcal pneumonia shows round to oval yeast with thick mucinous capsule creating a “halo” effect. |
TERMINOLOGY
Definitions
Lung infection caused by inhalation of Cryptococcus neoformans spores
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Organisms are found in soil, especially soil contaminated with pigeon droppings
CLINICAL ISSUES
Epidemiology
Incidence
Worldwide distribution; unknown incidence
Presentation
Acute pulmonary infection is most often asymptomatic
Progressive infection is associated with the following symptoms
Cough
Low-grade fever
Pleuritic pain
Weight loss
Natural History
Acute pulmonary infection can be asymptomatic or self-limited
Progressive infection is seen in immunocompromised hosts and involves lungs and meninges
Sequel of self-limited infection is formation of small subpleural fibrocaseous nodules without calcifications
Disease is most severe in immunocompromised patients
Treatment
Surgical approaches
Surgical excision of pulmonary nodules may be helpful to reduce mortality
Drugs
Amphotericin B
Fluconazole
Prognosis
Good response to antifungal agents
Infection with C. gattii in immunocompetent patients is associated with significant mortality despite therapy
IMAGE FINDINGS
General Features
Morphology
Focal pulmonary nodule or masses
Multifocal peripheral pulmonary nodules predominantly in upper lobes
Unilateral or bilateral parenchymal consolidation
Immunocompromised patients may show diffuse, bilateral, reticular, or nodular interstitial opacities or miliary nodules
Fibrosis and calcification are not associated with cryptococcosis
MACROSCOPIC FEATURES
General Features
Well-defined nodules (cryptococcomas) show central necrosis and cavitation but absence of calcifications
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