• is a pulmonary infection
• caused by
  • an atypical yeast-like fungus
    • most common opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS).
    • typically occurs at CD4 counts <200 cells/mm
      • (btw  Pneumocystis carinii  has been reclassified as Pneumocystis jiroveci)
    • virtually never seen in immunocompetent individuals
• resulting in
  • pulmonary infection
    •  insidious, dyspnea, non productive cough
    • but can be more dramatic
    • life threatening
  • dx
    • BAL (85-90 sensitivity)
    • The Organism

    • 

      Response by the Lungs – Fluid Filled Exudate

      

Radiology

• 90% of chest radiographs in patients with Pneumocystis pneumonia are abnormal
• Commonly Non Specific
• Characteristic Features
  •  shape – reticular changes
  • position – perihilar
  • character – small cysts – pneumatoceles
  • character – – subpleural blebs
  • associated fx –
    • uncommon pleural effusion
    • CD4 counts  <200/mm³

Perihilar Reticular Changes

Reticular Pattern

Pneumonic Infiltrate

Another Patient with a Pneumonic Infiltrate

 

• Position – Depends on use of prophylactic aerosolized meds
  • On Meds –
    • more prominent
      • upper lobes
  • Not On Meds More prominent
    • lower lobes
  • peripheral sparing – perihilar
• Character
  • ground glass
  • reticular opacities or
  • septal thickening
    • crazy paving
  • pneumatoceles 30%
    • varying
      • size
      • shape
      • wall thickness
  • consolidation
    • often patients without HIV
    • caused by inflammatory response
  • nodules
    • sometimes cavitate
  • lymphadenopathy
  • pleural effusion uncommon

Examples

Reticular Pattern with Ground Glass Dominantly in the Lower Lobes

 

• Cysts
  •  33%.
  • in the acute or
  • postinfective
  • range in
    • number – commonly multiple
    • size,
    • shape, and
    • position-  predilection for the upper lobes.
  • Cause
    • unclear,
    • ? release of elastase from alveolar macrophages,
    • ? vascular invasion with infarction;
    • ? cavitation obstruction of small airways,
      • a ball-valve effect.

35M with small PCP cysts

Spontaneous pneumothorax

• feature of PCP infection,
  • incidence 35% in patients with cysts
  • frequently bilateral
  • often refractory to chest tube Rx,
  • frequently need surgery eg pleurodesis
  • associated higher mortality rate,
    • especially in patients on ventilation.