Pneumocystis Carinii Pneumonia
Pneomocystis Jerovecii

General Considerations

• Most common cause of interstitial pneumonia in immunocompromised patients
• Organism
• Protozoan / fungus Pneumocystis carinii (jiroveci)
  

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 Findings

• 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
• 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

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
  

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
  

DDx

• Non-cardiogenic pulmonary edema
• TB
• MAI infection

Diagnosis

• Sputum collection
• Bronchoscopy with lavage
• Transbronchial or transthoracic or open lung Bx

Pneumocystis Pneumonia. There is diffuse, mostly reticular, interstitial lung disease greater at the bases. is a similar picture to that of congestive heart failure under other clinical circumstances.
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