251.2 📚 國考版

251.2.0.1 必背 — Pathogen

  • Pneumocystis jirovecii (renamed from P. carinii 2002)
  • Fungus (reclassified from protozoan)
  • Cannot culture in vitro

251.2.0.2 必背 — Risk Factors

  • HIV CD4 < 200 (#1)
  • Solid organ transplant
  • HSCT
  • High-dose corticosteroids
  • Chemotherapy
  • Anti-CD20 (rituximab)
  • Anti-TNF
  • Hematologic malignancy
  • Primary immunodeficiencies

251.2.0.3 必背 — Clinical

  • Insidious onset over weeks
  • Dry cough + progressive dyspnea + hypoxia + low fever
  • Exercise desaturation early
  • Bilateral perihilar interstitial CXR / ground-glass HRCT

251.2.0.4 必背 — Lab

  • β-D-glucan > 200 pg/mL
  • Elevated LDH
  • Lymphopenia (HIV)
  • Hypoxia + A-a gradient elevated

251.2.0.5 必背 — Diagnosis

  • BAL + immunofluorescence (gold standard)
  • Induced sputum (less sensitive in non-HIV)
  • PCR (sensitive but detects colonization)
  • CXR / HRCT characteristic

251.2.0.6 必背 — Treatment

  • TMP-SMX 15-20 mg/kg/d (TMP) divided q6h × 21 days (HIV) or 14-21 days (non-HIV)
  • Steroid if A-a > 35 or PaO2 < 70 (prednisone 40 mg bid × 5 → 40 qd × 5 → 20 qd × 11 days)
  • Steroid significantly reduces mortality in HIV-PJP

251.2.0.7 必背 — TMP-SMX Alternatives

  • Clindamycin + primaquine (G6PD screen)
  • Pentamidine IV (toxic)
  • Atovaquone PO (mild-moderate)
  • TMP + dapsone (G6PD screen)

251.2.0.8 必背 — Prophylaxis

  • HIV CD4 < 200: TMP-SMX 1 DS qd (also covers Toxo)
  • Transplant: × 6-12 mo post
  • Anti-CD20: case-by-case
  • Discontinue HIV: CD4 > 200 × 3-6 mo on ART

251.2.0.9 必背 — When to Start ART (HIV-PJP)

  • Within 2 weeks (vs 4-6 wk delay for cryptococcal meningitis)
  • Less IRIS risk than other OIs

251.2.0.10 必背 — Severity

  • Non-HIV-PJP often more severe + rapid onset + higher mortality
  • HIV-PJP: insidious, steroid critical