Definition
• A fungal infection caused by Candida spp.
Pathogenesis
• Candida are ubiquitous yeastlike fungi that normally inhabit the gastrointestinal and upper respiratory tracts without causing symptoms
• Opportunistic infections occur only when host immune system is compromised
Clinical features
Epidemiology
• Candida is the most common fungal pathogen in immunocompromised patients
• However, Candida pneumonia is rare and usually secondary to hematogenous dissemination or aspiration from oral cavity or upper respiratory tract
• Candida albicans is the most common pathogen
Presentation
• Patients usually present with fever, coughing, purulent sputum, and shortness of breath
Prognosis and treatment
• Poor prognosis with high mortality rate, even after intensive antifungal treatment
Pathology
Histology
• If infection is secondary to aspiration there is acute bronchopneumonia or granulomatous inflammation with associated Candida fungal organisms
• Miliary nodules of necrosis and inflammation around vessels are indicative of hematogenous spreading
• Organisms are budding yeasts with pseudohyphae
• Rarely, giant blastoconidia may be present
Immunopathology/special stains
• GMS and PAS stains help identify the presence of fungal organisms
Main differential diagnoses (see Table 6 in the Appendix)
• Histoplasmosis
• Aspergillosis
• Zygomycosis
• Giant blastoconidia should be distinguished from Cryptococcus, Blastomyces, or Paracoccidioides
Fig 1 Candidiasis. Candida pneumonia with granulomatous inflammation with multinucleated giant cell formation.
Fig 2 Candidiasis. Candida organisms with pseudohyphae and budding yeasts: H&E stain (A) and GMS stain (B). Note the presence of blastoconidia.