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Pneumonia in Immunocompromised Patients

By

Sanjay Sethi

, MD, University at Buffalo, Jacobs School of Medicine and Biomedical Sciences

Reviewed/Revised Feb 2024
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Pneumonia in immunocompromised patients is often caused by unusual pathogens that otherwise have limited virulence; it may also be caused by the same pathogens that cause pneumonia in immunocompetent patients, but manifests as more severe infection. Symptoms and signs depend on the pathogen and on the conditions compromising the immune system. Diagnosis is based on blood cultures and bronchoscopic sampling of respiratory secretions, sometimes with quantitative cultures. Molecular diagnostics are being increasingly used. Because of the variety of possible pathogens, identifying an etiology early is important. Treatment depends on the immune system defect and the pathogen.

The potential pathogens in patients with compromised immune system defenses are legion; they include those that cause community-acquired pneumonia Etiology Community-acquired pneumonia is defined as pneumonia that is acquired outside the hospital. The most commonly identified pathogens are Streptococcus pneumoniae, Haemophilus influenzae... read more Etiology as well as unusual pathogens. More than one pathogen may be involved. Likely pathogens depend on the type of defect in immune system defenses (see table ). However, respiratory symptoms and changes on chest x-rays in immunocompromised patients may be due to various processes other than (or in addition to) infection, such as pulmonary hemorrhage Diffuse Alveolar Hemorrhage Diffuse alveolar hemorrhage is persistent or recurrent pulmonary hemorrhage that originates from the lung parenchyma (ie, the alveoli) as opposed to the airways. There are numerous causes, but... read more Diffuse Alveolar Hemorrhage , pulmonary edema Pulmonary Edema Pulmonary edema is acute, severe left ventricular failure with pulmonary venous hypertension and alveolar flooding. Findings are severe dyspnea, diaphoresis, wheezing, and sometimes blood-tinged... read more Pulmonary Edema , radiation injury Focal radiation injury Ionizing radiation injures tissues variably, depending on factors such as radiation dose, rate of exposure, type of radiation, and part of the body exposed. Symptoms may be local (eg, burns)... read more Focal radiation injury , pulmonary toxicity due to cytotoxic or immunotherapy drugs, and tumor infiltrates.

Table

Symptoms and Signs of Pneumonia in Immunocompromised Patients

Symptoms and signs may be the same as those that occur with community-acquired pneumonia Symptoms and Signs Community-acquired pneumonia is defined as pneumonia that is acquired outside the hospital. The most commonly identified pathogens are Streptococcus pneumoniae, Haemophilus influenzae... read more Symptoms and Signs in immunocompetent patients. Symptoms may include malaise, chills, fever, rigor, cough, dyspnea, and chest pain. However, immunocompromised patients may have no fever or respiratory signs and are less likely to have purulent sputum if they are neutropenic. In some patients, the only sign is fever.

Pearls & Pitfalls

  • Have a high index of suspicion for pneumonia in patients who are immunocompromised because symptoms can be atypical or muted.

Diagnosis of Pneumonia in Immunocompromised Patients

  • Chest x-ray

  • Assessment of oxygenation

  • Sputum induction or bronchoscopy to obtain lower respiratory samples

  • Blood cultures

  • Pathogens predicted based on symptoms, x-ray changes, and type of immunodeficiency

Chest x-ray and assessment of oxygenation (usually by pulse oximetry) are done in immunocompromised patients with respiratory symptoms or signs, or fever. If an infiltrate or hypoxemia is present, diagnostic studies should be done. Chest x-ray may be normal in Pneumocystis jirovecii pneumonia Pneumocystis jirovecii Pneumonia Pneumocystis jirovecii, an atypical fungus, is a common cause of pneumonia in immunosuppressed patients, especially in those infected with human immunodeficiency virus (HIV) and in those... read more <i >Pneumocystis jirovecii</i> Pneumonia , but hypoxia or an increased alveolar-arterial oxygen gradient is usually present. If clinical suspicion of pneumonia is high and the chest x-ray is unrevealing, a chest CT scan should be done.

Sputum testing and blood cultures are done. Sputum testing should include Gram stain, mycobacterial and fungal stains and cultures, and sometimes testing for viruses (eg, polymerase chain reaction for cytomegalovirus in a patient who has had a transplant or in a patient with HIV). If signs, symptoms, or risk factors for Aspergillus infection Pathophysiology Aspergillosis is an opportunistic infection that usually affects the lower respiratory tract and is caused by inhaling spores of the filamentous fungus Aspergillus, commonly present in... read more Pathophysiology are present, serum galactomannan assay Diagnosis Diagnosis should be done.

It is important to aggressively pursue a microbiological diagnosis with induced sputum, bronchoscopy, or both, especially in patients with severe defects in immune function or failure to respond to broad-spectrum antibiotics.

Molecular testing that detects pathogen-specific nucleic acids or antigens is being increasingly used to determine the microbial cause.

Pathogen identification

Likely pathogens can often be predicted based on symptoms, x-ray changes, and the type of immunodeficiency. In patients with acute symptoms, the differential diagnosis includes bacterial infection, hemorrhage, pulmonary edema, a leukocyte agglutinin reaction to transfusion of blood products, and pulmonary emboli. An indolent time course is more suggestive of a fungal or mycobacterial infection, an opportunistic viral infection, P. jirovecii pneumonia Pneumocystis jirovecii Pneumonia Pneumocystis jirovecii, an atypical fungus, is a common cause of pneumonia in immunosuppressed patients, especially in those infected with human immunodeficiency virus (HIV) and in those... read more <i >Pneumocystis jirovecii</i> Pneumonia , a tumor, a cytotoxic drug reaction, or radiation injury.

X-rays showing localized consolidation usually indicate an infection involving bacteria (including Nocardia), mycobacteria, or fungi.

A diffuse interstitial pattern is more likely to represent a viral infection, P. jirovecii pneumonia, drug or radiation injury, or pulmonary edema.

Diffuse nodular lesions suggest mycobacteria, Nocardia species, fungi, or tumor.

Cavitary disease suggests mycobacteria, Nocardia species, fungi, or bacteria, particularly S. aureus.

In organ or bone marrow transplantation recipients with bilateral interstitial pneumonia, the usual cause is cytomegalovirus, or the disease is idiopathic.

A pleural-based consolidation is usually Aspergillus infection.

In patients with acquired immunodeficiency syndrome (AIDS), bilateral pneumonia is usually P. jirovecii pneumonia Pneumocystis jirovecii Pneumonia Pneumocystis jirovecii, an atypical fungus, is a common cause of pneumonia in immunosuppressed patients, especially in those infected with human immunodeficiency virus (HIV) and in those... read more <i >Pneumocystis jirovecii</i> Pneumonia . About 30% of patients with human immunodeficiency virus (HIV) infection have P. jirovecii pneumonia as the initial AIDS-defining diagnosis. Patients with HIV infection who are not on antiretroviral therapy are at high risk for developing this pneumonia if prophylaxis Postexposure prophylaxis (PEP) Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more Postexposure prophylaxis (PEP) is not given. Patients with HIV infection become vulnerable to P. jirovecii pneumonia when the CD4+ T cell count is < 200 cells/microL.

Treatment of Pneumonia in Immunocompromised Patients

  • Broad-spectrum antimicrobial therapy

The antimicrobial therapy depends on the immune system defect and the risk factors for specific pathogens. Consultation with an infectious diseases specialist is usually indicated. In patients with neutropenia, empiric treatment depends on the immune system defect, x-ray findings, and severity of illness. Generally, broad-spectrum antibiotics that are effective against gram-negative bacilli, Staphylococcus aureus, and anaerobes are needed, as for hospital-acquired pneumonia Treatment Hospital-acquired pneumonia (HAP) develops at least 48 hours after hospital admission. The most common pathogens are gram-negative bacilli and Staphylococcus aureus; antibiotic-resistant... read more . If patients with conditions other than HIV infection do not improve with 5 days of antibiotic therapy, antifungal therapy is frequently added empirically.

Therapies to enhance immune system function are an important adjunct for the treatment of pneumonia in immunocompromised patients.

Prevention of Pneumonia in Immunocompromised Patients

Therapies to enhance immune system function are indicated for the prevention of pneumonia in immunocompromised patients. For example, patients with chemotherapy-induced neutropenia should receive granulocyte-colony stimulating factor (G-CSF, or filgrastim), and patients with hypogammaglobulinemia due to an inherited or acquired disease (eg, multiple myeloma, leukemia) should receive IV immune globulin.

Patients with HIV and CD4+ T cell count < 200 cells/microL should receive daily prophylactic therapy with trimethoprim/sulfamethoxazole or other appropriate therapy.

Key Points

  • Consider typical as well as unusual pathogens in immunocompromised patients who have pneumonia.

  • If patients have hypoxemia or an abnormal chest x-ray, do further testing, including obtaining lower respiratory samples, either induced or bronchoscopically.

  • Begin with broad-spectrum antimicrobial therapy.

Drugs Mentioned In This Article

Drug Name Select Trade
Neupogen, Nivestym, Releuko, Zarxio
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NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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