Pneumocystis jirovecii pneumonia

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

Background

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

Fever (62%)
Dry cough
Shortness of breath (progressive from exertion only to at rest)

Differential Diagnosis

Acute dyspnea

Emergent

Pulmonary
- Airway obstruction
- Anaphylaxis
- Angioedema
- Aspiration
- Asthma
- Cor pulmonale
- Inhalation exposure
- Noncardiogenic pulmonary edema
- Pneumonia
- Pneumocystis Pneumonia (PCP)
- Pulmonary embolism
- Pulmonary hypertension
- Tension pneumothorax
- Idiopathic pulmonary fibrosis acute exacerbation
- Cystic fibrosis exacerbation
Cardiac
Other Associated with Normal/↑ Respiratory Effort
- Abdominal distension
- Anemia
- CO Poisoning
- Salicylate toxicity
- Diabetic ketoacidosis (DKA)
- Diaphragm injury
- Electrolyte abnormalities
- Epiglottitis
- Flail chest
- Hypotension
- Metabolic acidosis
- Pneumonia
- Pneumothorax/hemothorax
- Renal Failure
- Sepsis
- Toxic ingestion
Other Associated with ↓ Respiratory Effort

Non-Emergent

HIV associated conditions

HIV neurologic complications
HIV pulmonary complications
Ophthalmologic complications
- CMV Retinitis
- Herpes Zoster Ophthalmicus
Other
HAART medication side effects^[2]
- HAART-induced lactic acidosis
- Neuropyschiatric effects
- Hepatic toxicity
- Renal toxicity
- Steven-Johnson's
- Cytopenias
- GI symptoms
- Endocrine abnormalities

Evaluation

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.

Workup

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

Diagnosis

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

Management

Antibiotics

Require HCAP or CAP (ceftriaxone and azithromycin) coverage as well^[3]

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

Prophylaxis

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

Corticosteroids

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

Disposition

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

References

↑ 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.
↑ 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.
↑ 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.
↑ CDC Guidelines for Prophylaxis Against Pneumocystis carinii Pneumonia for Children Infected with Human Immunodeficiency Virus http://www.cdc.gov/mmwr/preview/mmwrhtml/00001957.htm
↑ 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.
↑ Wilken A, Feinberg J. Pneumocystis carinii Pneumonia: A Clinical Review. Am Fam Physician. 1999 Oct 15;60(6):1699-1708. http://www.aafp.org/afp/1999/1015/p1699.html.

Authors:

[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 http://www.cdc.gov/mmwr/preview/mmwrhtml/00001957.htm

[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. http://www.aafp.org/afp/1999/1015/p1699.html.

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