Pneumocystis Pneumonia



  • Originally called Pneumocystis carinii pneumonia, then renamed Pneumocystis jirovecii but still referred to as PCP
  • Most common opportunistic infection in patients with HIV, even with PCP prophylaxis and antiretroviral therapy
  • Believed to be transmitted by respiratory-aerosol route:
    • Cysts colonize respiratory tract
    • Cysts rupture and multiple trophozoites release and form foamy exudate in alveoli
  • Most cases are believed to represent reactivation of latent disease, although person-to-person transmission suggested
  • Actual mode of transmission is unclear


  • Pneumocystis is classified as a fungus
  • Pneumocystis occurs in hosts with altered cellular immunity:
    • HIV infection (most common, especially when CD4 count <200 cells/mm3)
    • Cancer
    • Corticosteroid treatment
    • Organ transplantation
    • Malnutrition
Exists within the alveoli of the lung
Pediatric Considerations
PCP in children is typically more severe

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