Author:
Alan M.Kumar
Christine A.Babcock
Description
- Originally called Pneumocystis carinii pneumonia, then renamed Pneumocystis jirovecii but still referred to as PCP
- Most common opportunistic infection in patients with HIV, even with PCP prophylaxis and antiretroviral therapy
- Believed to be transmitted by respiratory-aerosol route:
- Cysts colonize respiratory tract
- Cysts rupture and multiple trophozoites release and form foamy exudate in alveoli
- Most cases are believed to represent reactivation of latent disease, although person-to-person transmission suggested
- Actual mode of transmission is unclear
Etiology
- Pneumocystis is classified as a fungus
- Pneumocystis occurs in hosts with altered cellular immunity:
- HIV infection (most common, especially when CD4 count <200 cells/mm3)
- Cancer
- Corticosteroid treatment
- Organ transplantation
- Malnutrition
Exists within the alveoli of the lung
Pediatric Considerations |
| PCP in children is typically more severe |
Signs and Symptoms
- Subacute presentation
- Up to 7% of patients can be asymptomatic
- Patients on inhaled pentamidine prophylaxis may have milder symptoms:
- Increased incidence of pneumothorax
- Increased incidence of extrapulmonary disease
History
- Fever
- Cough with none or minimal amount of white sputum
- Dyspnea on exertion or at rest:
- Progressive over days (most common in non-HIV-immunocompromised hosts)
- Indolent, developing over weeks to months (more common in HIV-positive hosts)
- Oxygen desaturation with exercise
- Chills
- Fatigue
- Weight loss
- Chest pain
Physical Exam
- Tachypnea
- Tachycardia
- Crackles and rhonchi on lung exam
- Lung exam may be normal
Essential Workup
- CBC
- Electrolytes
- Arterial blood gas (ABG)
- Lactate dehydrogenase (LDH)
- Blood cultures
- Chest x-ray
Diagnostic Tests & Interpretation
Lab
- ABG:
- Obtain in all cases of PCP
- Calculate the alveolar-arterial (A-a) gradient (usually increased)
- Adjunctive corticosteroid therapy for A-a gradient >35 mm Hg or PaO2<70 mm Hg
- LDH:
- Elevated in HIV-positive patients with PCP compared to non-PCP pneumonia
- Higher levels correlate with poorer prognosis
Imaging
- Chest radiograph:
- Classically reveals bilateral interstitial or central alveolar infiltrates
- Radiograph normal in up to 25% of patients with PCP
- Early or mild infection associated with decreased sensitivity
- Atypical presentations include:
- Lobar infiltrates
- Cysts
- Pneumothoraces
- Pleural effusions
- Nodular infiltrates
- Prophylaxis with aerosolized pentamidine is a risk factor for developing predominantly upper lobe
- Chest radiograph abnormalities can persist for months after treatment
- High-resolution chest CT:
- High sensitivity for PCP in HIV-positive patients
- Reveals patchy ground-glass attenuation
Diagnostic Procedures/Surgery
- Induced sputum:
- Definitive diagnosis requires presence of Pneumocystis organisms in an appropriately stained respiratory specimen
- Specificity approaches 100%, but sensitivity depends on quality of induced sputum and lab expertise
- Less sensitive in patients on inhaled pentamidine prophylaxis and non-HIV-positive patients
- Bronchoalveolar lavage:
- Perform if the induced sputum is nondiagnostic and the suspicion for PCP is still high
- Sensitivity 80-100%
Differential Diagnosis
Constellation of dyspnea, fever, diffuse radiographic infiltrates, minimal or nonproductive cough, and slow progressive course suggests atypical cause of the pneumonia:
- Chlamydia pneumoniae
- Legionella
- Mycoplasma
- Tuberculosis
- Viral pneumonia (especially cytomegalovirus)
Prehospital
Provide supplemental oxygen for symptomatic patients
Initial Stabilization/Therapy
- ABCs
- Provide adequate oxygenation with nasal cannula up to 100% nonrebreather
- Perform endotracheal intubation in those with refractory hypoxemia despite maximal oxygenation or hypercarbic respiratory failure
- At least 500-1,000 cc 0.9% normal saline IV bolus for hypotension, sepsis, dehydration
ED Treatment/Procedures
- Initiate antibiotics:
- IV Bactrim is the first-line agent
- IV pentamidine for those who cannot tolerate Bactrim
- Oral therapy is an option for well-appearing patients
- Alternative regimens include trimethoprim-dapsone, clindamycin-primaquine, and atovaquone
- Continue antibiotics for 21 d
- Adjunctive corticosteroids in patients with A-a gradient >35 mm Hg or PaO2<70 mm Hg:
- Must start within first 72 hr of treatment
- Isolate suspected PCP patients from others who are immunocompromised
Medication
- Atovaquone: 750 mg (peds: Dosing not established) PO q12h
- Clindamycin/primaquine: Clindamycin 900 mg (peds: Dosing not established) IV q8h or 300-450 mg PO q6h and primaquine 15-30 mg (peds: Dosing not established) PO per day
- Pentamidine: 4 mg/kg/24 hr IV over 1 hr (peds: 3-4 mg/kg IM or IV once/day for 21 d)
- Prednisone: 40 mg (peds: Dosing not established) PO q12h for 5 d, 40 mg PO per day for 5 d, then 20 mg PO per day for 11 d (IV methylprednisolone at 75% of the prednisone dose may be substituted)
- Trimethoprim/dapsone: Trimethoprim 15-20 mg/kg/d IV div q8h + dapsone 100 mg PO per day (peds: Dosing not established)
- Trimethoprim/sulfamethoxazole (Bactrim): Trimethoprim 15-20 mg/kg/d IV div q6h and sulfamethoxazole 100 mg/kg/d IV div q6h (peds: Dosing same)
Pediatric Considerations |
- Treatment of choice is IV trimethoprim/sulfamethoxazole, followed by IV pentamidine
- Dosing for alternative medications not yet established (consult pediatric infectious disease specialist)
|
Disposition
Admission Criteria
- Moderate to severe disease (PaO2<70 mm Hg or A-a gradient >35 mm Hg)
- Inability to digest medications
- Inability to return for careful follow-up
Discharge Criteria
- Nontoxic clinical appearance
- Mild disease state (no hypoxemia or A-a gradient)
- Ability to tolerate medications
- Close follow-up arranged
- If results of induced sputum are not available, add macrolide to empirical regimen
Follow-up Recommendations
Close follow-up must be arranged with infectious disease specialist to allow for outpatient management
- CatherinotE, LanternierF, BougnouxM, et al. Pneumocystis jirovecii pneumonia . Infect Dis Clin North Am. 2010;24(1):107-138.
- HuangL, QuartinA, JonesD, et al. Intensive care of patients with HIV infection . N Engl J Med. 2006;355(2):173-181.
- KovacsJA, MasurH. Evolving health effects of pneumocystis: One hundred years of progress in diagnosis and treatment . JAMA. 2009;301(24):2578-2585.
- ThomasCF Jr, LimperAH. Pneumocystis pneumonia . N Engl J Med. 2004;350(24):2487-2498.
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