Pneumocystis jirovecii pneumonia

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Background

  • Thought to be caused by opportunistic protozoan vs. fungal infection seen most commonly in immunocompromised patients
    • Risk factors: CD4 count < 200, immunosuppressive medications, cancer, primary immunodeficiencies, severe malnutrition

Clinical Features

  • Non-HIV infected patients tend to present with fever, dry cough, and respiratory failure
  • HIV infected patients commonly present with dry cough, weakness, and chest pain lasting > 2 weeks
  • Fever - 62%
  • Crackles - 50%
  • High percentage of normal physical exams

Diagnosis

  • Chest X-ray
    • Can be normal in 25% of cases
    • May see asymmetry, cysts, nodules, bullae, or pleural effusions
  • CT Chest
    • High sensitivity ~ 100%
    • Specificity 89%
    • May see ground glass infiltrative pattern
  • Lactate dehydrogenase level
    • Suggestive of PCP
    • may be used as prognostic indicator
  • Immunofluorescent antibody staining
    • Staining of sputum samples yields 100% specificity, but 50-90% sensitivity
    • Staining of bronchoalveolar lavage samples has 97% diagnostic yield

Work-Up

  • CBC
  • Complete Metabolic Panel
  • Lactate dehydrogenase
  • Arterial blood gas
  • CD 4 count
  • Chest x-ray
  • Alveolar-arterial gradient
    • P(A-a)O2 = 145 – PaCO2 – PaO2 (normal is <10 in young, healthy pts)

DDX

Treatment

  • Trimethoprim-Sulfamethoxazole
    • Oral/intravenous regimen: Trimethoprim 20 mg/kg/day + Sulfamethoxazole 75 mg/kg/day divided bid-tid x21 days
      • Average adult - Bactrim DS 2 tabs PO q8hrs
    • Consider intravenous regimen for:
      • Severe respiratory distress
      • A-a gradient above 45 mm Hg
      • PaO2 < 60 mm Hg
  • Steroids
    • Oral regimen: Prednisone 40 mg PO BID x5 days with taper
    • Indicated for:
      • A-a gradient above 35 mm Hg
      • PaO2 < 70 mm Hg
  • Other regimens
    • Pentamidine (IV)
      • Side effects: renal failure, hypoglycemia, hypotension, induction of diabetes
    • Clindamycin + primaquine (IV/PO)
      • Caution when using primaquine in patients with G6P deficiency
    • Atovaquone (PO)
      • Indicated only in mild cases of PCP
    • Dapsone + TMP (PO)
      • Caution when using dapsone in patients with G6P deficiency

Disposition

  • Symptoms usually worsen after 2-3 days of treatment
  • Patients with disease severe enough to warrant IV therapy or corticosteroids should be admitted for close monitoring

Source

Uptodate

Rosen