Pneumocystis Jirovecii Pneumonia

Pneumocystis jirovecii was previously known as Pneumocystis carinii, and is sometimes still referred to by the “PCP” acronym.

Severe fungal pneumonia caused by Pneumocystis Jirovecii, which is essentially confined to the severely immunocompromised:

After its rechristening, PJP was spelled jiroveci (after a Czech parasitologist) as it was at the time believed to be a protozoa.

The enigmatic organism was later confirmed to be a fungus, and therefore naming rights passed from the International Code of Zoological Nomenclature (ICZN) to the International Code of Nomenclature of algae, fungi, and plants (ICNafp) which requires the substantival epithet to be formed with a second -i. Hence, jirocevii.

Epidemiology and Risk Factors

Pathophysiology

Pneumocystis Jirovecii differs from most fungi as it has cholesterol rather than ergosterol in the cell wall, which results in:

  • Minimal extrapulmonary invasion
  • Immunity to most classical antifungals
    • No response to amphotericin or azoles
    • Highly resistant to echinocandins

Aetiology

Clinical Features

Usually insidious:

  • Non-productive cough
  • Dyspnoea
  • Fever
  • Fatigue
  • Weight loss
  • Crepitations are rare

Diagnostic Approach and DDx

  • Alternative diagnosis for respiratory failure is present in ~15%

Investigations

Laboratory:

  • Blood
    • ↑ LDH
      Common, non-specific.
  • Sputum
    • PJP PCR
    • Adequate non-invasive sampling requires induced sputum
      • Hypertonic saline nebuliser provokes bronchorrhoea and extensive coughing
      • Time consuming
      • Requires good operator skill
    • Bronchoscopy with BAL
      Diagnostic in >90%.

Organisms persist for days or weeks, so unlike many other infections, treatment can start prior to sampling if diagnostic suspicion is high enough.

Imaging:

  • CXR
    • Normal in 10%
    • Perihilar and interstitial shadowing
      Often subtle and missed.

Management

Resuscitation:

Specific therapy:

  • Pharmacological
    • Antimicrobials
      • Trimethoprim/Sulphamethoxazole (cotrimoxazole) 20+100mg/kg daily for 3 weeks
        Dose ↓ by 25% if WCC falls
      • Pentamidine 4mg/kg IV daily
        Only if cotrimoxazole not tolerated. Note that cotrimoxazole is a much better agent, and so mild hypersensitivity reactions are best put up with.
    • Corticosteroids
      For patients with HIV infection or ↑ A-a gradient >35mmHg.
      • Prednisolone
        • 40mg BD for 5 days
        • 20mg BD for 5 days
        • 20mg daily until antibiotic treatment completed
  • Physical
  • Procedural

Supportive care:

Disposition:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

  • B
    • Pneumothorax

Prognosis

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.