Pneumocystis carinii Pneumonia

1. See Also
   1. Pneumocystis prophylaxis
2. Epidemiology
   1. CD4 Count related risk of Pneumocystis
      1. CD4 Count >200: Risk <1% over 6 months
      2. CD4 Count <200 (Accounts for 85-95% of cases)
         1. Risk 6% over 6 months
         2. Risk 18% at 1 year
   2. United States Incidence: 20,000 to 60,000 cases/year
   3. HIV without prophylaxis develops PCP sometime: 75-90%
3. Pathophysiology
   1. Pneumocystis defies classification
      1. Both Protozoan and Fungal Characteristics
   2. Recently renamed as Pneumocystis jiroveci
   3. Ubiquitous organism
      1. Most humans and mammals exposed early in life
   4. Clinical infection may represent reactivation
4. Symptoms
   1. Symptoms usually develop over 1-2 weeks
      1. Typical Bacterial Pneumonia develops over 3-5 days
   2. Initial Symptoms (occur in 66%, often subtle)
      1. Fever
      2. Cough
      3. Dyspnea
   3. Pronounced Symptoms
      1. Sputum production
      2. Chest Pain
      3. Chills
5. Labs
   1. White Blood Cell Count Normal
      1. Elevated WBC Count in typical Bacterial Pneumonia
   2. Sputum induction
      1. Efficacy
         1. Sensitivity 80-90% for Pneumocystis
         2. Negative Predictive Value only 50-60%
      2. Examination stains
         1. Methenamine silver
         2. Giemsa stains
6. Radiology: Chest XRay
   1. Diffuse bilateral Interstitial Infiltrates (80-95%)
      1. Seen in Tuberculosis
      2. Seen in Bacterial Pneumonia
   2. Focal infiltrates rarely seen with Pneumocystis
   3. Images
      1. From MedPix with permission.
      2. From MedPix with permission.
7. Prognosis
   1. Treated appropriately: 60-90% survive
   2. Untreated: Uniformly fatal
8. Management: General
   1. Treatment Duration for 14-21 days
9. Management: Antibiotics
   1. First Line treatment
      1. Bactrim PO or IV (15 mg/kg of trimethoprim/day)
         1. Adverse reactions occur in 40-60% within 3 weeks
   2. Other agents (Bactrim intolerance)
      1. Pentamidine 4 mg/kg/day IV or IM
      2. Atovaquone 750 mg PO bid
      3. Dapsone and Trimethoprim
         1. Indicated for mild-moderate Pneumocystis
         2. Fewer dose limiting adverse reactions
      4. Primaquine and Clindamycin
         1. Indicated for intolerance for other regimens
10. Management: Corticosteroids
    1. Efficacy
       1. Prevents alveolar inflammation and exudation
       2. Results from the killing of Pneumocystis organisms
       3. Reduces the risk of intubation and death by 50%
    2. Indications (based on Arterial Blood Gas)
       1. Arterial pO2 < 70 mmHg
       2. A-a Gradient > 35 mmHg on room air
    3. Dosing: Prednisone
       1. Start: 40 mg bid for 5 days
       2. Next: 40 mg qd for 5 days
       3. Taper: 20 mg qd for 10 days
11. Prevention: Pneumocystis prophylaxis Indications
    1. CD4 Count <200 cells
    2. HIV patients with respiratory symptoms
12. References
    1. Weller (2001) BMJ 322:1350-4