Clinical Features
- Insidious onset (weeks in HIV+) vs rapid/fulminant onset (days in non-HIV).
- Classic triad:
- Progressive exertional dyspnea
- Dry/nonproductive cough
- Fever
- Profound hypoxemia disproportionate to physical exam findings (pulmonary auscultation often normal or shows minimal faint crackles). c
Diagnosis
- Initial Lab Testing:
- Serum LDH: Elevated (> 220 U/L) in > 90% of cases (high sensitivity, low specificity).
- ABG: Hypoxemia, ↑ A-a oxygen gradient (≥ 35 mmHg).
- Serum (1,3)-β-D-glucan: High sensitivity; supports diagnosis if positive.
- CXR/CT: Bilateral, diffuse “ground-glass” opacities.
- Definitive Dx: Organisms seen on bronchoalveolar lavage (BAL) sample.
- Stains: Methenamine silver stain shows disc-shaped or “crushed ping-pong ball” cysts.
Management
- Emergency & Oxygenation:
- Supplemental O₂ to maintain SaO₂ > 92%.
- Adjuvant Corticosteroids (CRITICAL HIGH-YIELD STEP): c
- Indication: PaO₂ < 70 mmHg OR A-a gradient ≥ 35 mmHg on room air.
- Timing: Administer prior to or concurrently with antibiotic therapy (prevents inflammatory flare from fungal lysis).
- Regimen: IV Methylprednisolone or PO Prednisone tapered over 21 days.
- First-Line Treatment:
- TMP-SMX (IV or PO high-dose) x 21 days.
- Alternative Treatment (Sulfa Allergy / Severe Intolerance):
- Mild-to-Moderate disease: Atovaquone OR TMP + Dapsone.
- Moderate-to-Severe disease: IV Pentamidine OR Clindamycin + Primaquine.
- Prophylaxis (Prevention):
- Indications:
- HIV w/ CD4 < 200 cells/mm³, CD4 percentage < 14%, or history of oral candidiasis.
- Solid organ transplant / chronic high-dose steroid therapy.
- First-line: TMP-SMX (1 DS or 1 SS tablet daily).
- Alternatives: Dapsone, Atovaquone, or Aerosolized Pentamidine.
- Discontinue in HIV when CD4 > 200 cells/mm³ for > 3 months on ART.