Pneumocystis jirovecii pneumonia

(Redirected from PCP PNA)

Note: this page is about the infection. For the drug PCP, see phencyclidine toxicity


  • Formerly known known as "pneumocystis carinii pneumonia" (i.e. "PCP")
  • An atypical fungus [1]
  • Most common opportunistic infection in AIDS patients
    • Most common identifiable cause of death

Risk factors

  • CD4 < 200
  • Immunosuppressive medications
  • Cancer
  • Primary immunodeficiencies
  • Severe malnutrition

Clinical Features

Differential Diagnosis

Acute dyspnea



HIV associated conditions


PA CXR and CT of pneumocystis jirovecii pneumonia before (A and B) and after (C and D) treatment.
CT of Pneumocystis jirovecii pneumonia, showing small nodular lesions surrounded by diffuse GGO.
CT of Pneumocystis jirovecii pneumonia, showing diffuse GGO with interlobular septal lines and cyst formation.
CT of Pneumocystis jirovecii pneumonia showing diffuse GGO with inhomogeneous distribution unrelated to secondary lobules and with spared peripheral lung parenchyma.


  • CBC
  • Chemistry
  • LDH elevation - sensitive but not specific
  • ABG
  • CD4 count
  • CXR - bat wing appearance (bilat interstitial infiltrates)
  • A-a gradient
    • P(A-a)O2 = 150 – (PaCO2/0.8) – PaO2 at sea level on RA (normal is <10 in young, healthy patients)
    • Increased in PCP pneumonia secondary to decreased diffusion thru thick aveoli


  • Imaging
    • CXR
      • Normal in 25% of cases
      • Diffuse, interstitial infiltrates
    • CT Chest
      • Sn 100%, Sp 89%
      • May see ground glass infiltrative pattern



Mild Disease

  • TMP/SMX 2 DS tablets PO q8hrs daily OR
    • High incidence of allergy in HIV
  • Dapsone 100mg PO once daily + TMP 5mg/kg PO q8hrs OR
    • caution: dapsone can cause methemoglobinemia
  • Atavaquone 750mg PO q12hrs OR
  • Primaquine 30mg PO q24hrs + Clindamycin 450mg PO q8hrs

Severe Disease

  • TMP/SMX 5mg/kg IV q8hrs daily x 21 days OR
  • Pentamidine 4mg/kg IV daily infused over 60 minutes OR
    • Watch for side effects of hypoglycemia and hypotension
  • Primaquine 30mg PO once daily + Clindamycin 900mg IV q8hrs daily


  • TMP/SMX 1 double strength tablet daily, but one single strength tablet daily or one double-strength three times weekly is acceptable.[4]


When used early, found to reduce the risk of progression of hypoxemia, respiratory failure, and death. [5]

  • Only in patients with HIV with severe respiratory parameters:
    • Room air PaO2 < 70 mmHg
    • OR A-a gradient > 35 mmHg
  • Treatment schedule for moderate to severe PCP[6]
    • Day 1-5: 40mg prednisone BID
    • Day 6-10: 40mg prednisone once daily
    • Day 11-21: 20mg prednisone once daily
    • Patients too ill to take PO may take equivalent IV methylprednisolone


  • Symptoms usually worsen 2-3d after start of treatment
  • Patients with disease severe enough to warrant IV therapy or steroids should be admitted


  1. Chapman, M., Muse, V., Mojica, J., & Anahtar, M. (2021). Case 35-2021: A 50 Year Old woman with Pain in the Left Upper Quadrant and Hypoxemia. The New England Journal of Medicine, 385(21), 1995–2001.
  2. Gutteridge, David L MD, MPH, Egan, Daniel J. MD. The HIV-Infected Adult Patient in The Emergency Department: The Changing Landscape of the Disease. Emergency Medicine Practice: An Evidence-Based Approach to Emergency Medicine. Vol 18, Num 2. Feb 2016.
  3. Rothmans RE, Marco CA, Yang S. Human immunodeficiency virus infection and acquired immunodeficiency syndrome, in Tintinalli JE, Stapczynski JS, Ma OJ, et al (eds): Tintinalli’s Emergency Medicine, ed 7. New York, The McGraw-Hill Companies Inc., 2011.
  4. CDC Guidelines for Prophylaxis Against Pneumocystis carinii Pneumonia for Children Infected with Human Immunodeficiency Virus
  5. Chapman, M., Muse, V., Mojica, J., & Anahtar, M. (2021). Case 35-2021: A 50 Year Old woman with Pain in the Left Upper Quadrant and Hypoxemia. The New England Journal of Medicine, 385(21), 1995–2001.
  6. Wilken A, Feinberg J. Pneumocystis carinii Pneumonia: A Clinical Review. Am Fam Physician. 1999 Oct 15;60(6):1699-1708.