Pneumocystis Pneumonia (PCP)

Question 1

What is PCP?

Answer 1

One of the leading causes of opportunistic infections among HIV-infected persons with low CD4 cell counts, such as those who are unaware of their HIV diagnoses or are not receiving medical care.

Question 2

What is pneumocystis categorized as?

Answer 2

Fungus (previously recognized as protozoan)

Question 3

What kind of organisms are pneumocystis?

Answer 3

Atypical fungi as they do not grow in fungal culture

Question 4

Life cycle of pneumocystis

Answer 4

• The life cycle consists of the trophic form, a precystic form, and the cystic form.
• The trophic form predominates over the cystic form during infection**

Question 5

Nomenclature change for pneumocystis

Answer 5

• P. jirovecii is now designated as the species name to use in publications and references to human infections.
• The abbreviation of “PCP” is still used to refer to the clinical entity of “Pneumocystis Pneumonia”

Question 6

PCP transmission

Answer 6

• The primary mode of transmission of P. jirovecii is via the airborne route.
• Animal and human studies have shown clearance of the organism, and there is increasing evidence of transmission from person to person and possibly through environmental reservoirs

Question 7

Where does pneumocystis reside in the body?

Answer 7

Almost exclusively within the alveoli of the lung

Question 8

PCP risk factors

Answer 8

**Main risk factor for PCP is advanced immunosuppression in patients not taking antiretroviral therapy.

Other risk factors include:

• CD4 cell count less than 200 cells/microL**
• CD4 cell percentage of less than 14%
• Previous episodes of PCP
• Oral thrush
• Recurrent bacterial pneumonia
• Unintentional weight loss
• Higher plasma HIV RNA levels

Question 9

Clinical manifestations of PCP

Answer 9

• Fever (80 to 100 percent), cough (95 percent), and dyspnea (95 percent) progressing over days to weeks
• Avg. pt has pulmonary symptoms for about 3 weeks before presentation
• Cough is generally nonproductive

Question 10

What are MC findings on physical exam?

Answer 10

Fever and tachypnea

Question 11

What is a common co-infection with PCP?

Answer 11

Oral thrush

Question 12

Lab findings for PCP

Answer 12

• Low CD4 counts < 200cells/micorL
• Oxygenation: hypoxia occurs with progression and oxygen desaturation that occurs during exercise is highly suggestive of Dx
• Lactate dehydrogenase level (LDH) – elevated in 90% of infected and rising LDH level despite tx is a poor prognosis
• Beta-D-glucan levels-1-3-beta-d-glucan is a component of the cell wall of P. jirovecii, we use this assay to support the diagnosis

Question 13

Radiographic manifestations of PCP

Answer 13

• CXR are initially normal in up to one-fourth of patients with PCP
• The MC radiographic abnormalities are diffuse, bilateral, interstitial, or alveolar infiltrates
• High resolution computed tomography (HRCT) has a high sensitivity for PCP among HIV-positive patients with presence of patchy or nodular ground-glass attenuation
• (-) HRCT makes dx of PCP highly unlikely

Question 14

Diagnosis of PCP

Answer 14

A definitive diagnosis of PCP requires visualization of the cystic or trophic forms in respiratory secretions since Pneumocystis cannot be cultured

Question 15

Diff dx for PCP

Answer 15

• Tuberculosis
• Nontuberculous mycobacteria
• Fungi
• Toxoplasma
• CMV
• Influenza
• Kaposi’s sarcoma

Question 16

When do extrapulmonary manifestations occur in PCP?

Answer 16

• Rare and have been observed in patients with very advanced HIV infection
• When multiple noncontiguous sites are involved, pulmonary disease is often present as well

Question 17

Treatment of PCP

Answer 17

• Antimicrobial therapy directed against P. jirovecii
• Some patients will require adjunctive corticosteroids
• ART should be initiated to restore cellular immunity

Question 18

Severe disease treatment

Answer 18

IV trimethoprim-sulfamethoxazole (TMP-SMX), if unable to take use clindamycin-primaquine

Question 19

When is PCP prophylaxis needed?

Answer 19

CD4 count < 200 cells/microL

CD4 percentage < 14%

Question 20

List PCP Prophylaxis

Answer 20

In patients without sulfa allergy we use TMP-SMX:
*One double-strength (DS) tab PO daily to patients who require antimicrobial therapy to prevent toxoplasmosis (i.e., those who have a CD4 count < 100 cells/microL and are IgG-positive for Toxoplasma gondii)

Question 21

PCP prophylaxis in pt who can’t tolerate Bactrim

Answer 21

For patients with sulfa allergy or once who are unable to tolerate TMP-SMX we use dapsone
*Dapsone 50 mg TID or Dapsone 100 mg daily

Question 22

What co-morbidity should you consider when prescribing dapsone?

Answer 22

Patients should be screened for glucose-6-phosphate dehydrogenase (G6PD) deficiency since patients with G6PD-deficiency are the risk for developing hemolytic anemia with dapsone