Pneumocystis Carinii Pneumonia

PCP
 

• Most common cause of interstitial pneumonia in immunocompromised patients
• Organism
  • Protozoan / fungus Pneumocystis carinii
    
• Predisposed
  • AIDS
  • Debilitated
  • Premature infants
  • Children with hypogammaglobulinemia
  • Other immunocompromised patients
    • Congenital immunodeficiency syndromes
    • Lymphoproliferative disorders
    • Organ transplant recipients
    • Patients on long-term corticosteroid therapy
    • Patients on chemotherapy for cancer
      
• Associated infections
  • CMV
  • Mycobacterium avium-intracellulare (MAI)
  • Herpes simplex
    
• Clinical
  • Severe dyspnea and cyanosis
  • Subacute insidious onset of malaise and slight cough (frequent in AIDS patients)
  • Respiratory failure
  • WBC slightly elevated (polys)
  • Lymphopenia (50%) indicates poor prognosis
    
• Imaging findings
  • Normal CXR in 10-40%
  • Bilateral diffuse symmetric finely granular / reticular interstitial / airspace infiltrates in 80%
    • Characteristic central location
    • Rapid progression to diffuse airspace disease
      • Resembles non-cardiogenic pulmonary edema

PCP

• Pleural effusion and hilar lymphadenopathy are uncommon
• Atypical pattern in 5%
  • Isolated lobar disease / focal parenchymal opacities
  • Lung nodules ± cavitation
  • Hilar / mediastinal lymphadenopathy
  • Thin- / thick-walled cysts
  • Cavities with predilection for upper lobes
    
• Course
  • Usually responds to therapy in 5-7 days
  • Effect of prophylactic use of aerosolized pentamidine
    • Redistribution of infection to upper lobes
      
• Complications
  • Cystic lung disease
    • Central location to cysts
  • Spontaneous pneumothorax, frequently bilateral (6-7%)
  • Disseminated extrapulmonary disease (1%)
  • Punctate / rimlike calcifications within enlarged lymph nodes and abdominal viscera
    
• CT findings
  • Patchwork pattern (56%)
    • Bilateral, asymmetric patchy mosaic appearance
  • Ground-glass pattern (26%)
    • Bilateral, diffuse air-space disease in symmetric distribution
  • Interstitial pattern (18%)
    • Bilateral, symmetric / asymmetric, reticular markings (thickening of lobular septa)
  • Abnormal air-filled spaces (38%)
    • Pneumatocoeles
      • Thin-walled spaces without lobar predilection resolving within 6 months
    • Subpleural bullae due to emphysema
    • Thin-walled cysts
    • Necrosis of pneumocystis granuloma
    • Pneumothorax (13%)
  • Lymphadenopathy (18%)
  • Pleural effusion (18%)
    
• Pulmonary nodules and cavities
  • Usually due to malignancy
    • Leukemia, lymphoma
    • Kaposi sarcoma
    • Metastasis
    • Or septic emboli
  • Pulmonary cavities usually due to superimposed fungal / mycobacterial infection
    
• Nuclear medicine
  • Bilateral and diffuse Ga-67 uptake without mediastinal involvement prior to roentgenographic changes
    
• DDx
  • Non-cardiogenic pulmonary edema
  • TB
  • MAI infection
     
• Diagnosis
  • Sputum collection
  • Bronchoscopy with lavage
  • Transbronchial or transthoracic or open lung Bx

Dahnert 4^th edition