What is Pneumonia?
Pneumonia is an inflammation in the lungs, usually caused by an infection, that affects the alveoli and distal airways, characterized by fever, cough, difficulty breathing, and radiographic evidence of lung infiltrates. 1
Clinical Definition and Diagnosis
- Pneumonia is defined clinically as the presence of fever and/or acute respiratory symptoms, including new onset of fever, purulent sputum, and leukocytosis, along with confirmatory chest radiographic findings 2
- Diagnosis requires a compatible clinical picture (fever, cough, and/or auscultatory findings such as rales and/or evidence of pulmonary consolidation) together with chest radiographic findings and, when possible, isolation of the causative pathogen(s) 2
- In children, bacterial pneumonia should be considered when there is fever >38.5°C together with chest recession and a respiratory rate >50/min in those up to 3 years of age 2
- For older children, a history of difficulty breathing is more helpful than clinical signs 2
Types of Pneumonia
Based on Acquisition Setting:
- Community-acquired pneumonia (CAP): Occurs in previously healthy individuals outside of the hospital setting 2
- Hospital-acquired pneumonia: Develops after 48 hours of hospitalization that was not present at admission 2
- Ventilator-associated pneumonia: A subset of hospital-acquired pneumonia occurring in mechanically ventilated patients 2
Based on Pathogen:
- Bacterial pneumonia: Commonly caused by Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae 2
- Viral pneumonia: Can be primary or secondary to influenza, with respiratory syncytial virus being common in children 2
- Atypical pneumonia: Caused by organisms like Mycoplasma pneumoniae, characterized by slow progression, malaise, and low-grade fever 2, 3
Clinical Presentation
Symptoms:
- Fever (typically >38.5°C) 2, 3
- Cough (initially dry, may become productive) 2
- Dyspnea (breathlessness) 2
- Chest pain 2
- Abdominal pain (especially in children, reflecting referred pain from diaphragmatic pleura) 2
- Headache and arthralgia (common in mycoplasma pneumonia) 3
Signs:
- Tachypnea (increased respiratory rate) 2
- Chest recession/indrawing 2
- Crackles on auscultation 3
- Wheeze (if present in a preschool child, primary bacterial pneumonia is unlikely) 2
- Cyanosis (in severe cases) 2
Pathogen-Specific Presentations
- Pneumococcal pneumonia: Starts with fever and tachypnea; cough occurs when lysis is present; characterized by fever, breathlessness, tachypnea, indrawing, and unwell appearance 2
- Staphylococcal pneumonia: Rare in developed countries, almost exclusively a disease of infants, can complicate influenza in older children 2
- Mycoplasma pneumonia: Common in school-aged children with fever, arthralgia, headache, cough, and crackles 3
- Primary viral pneumonia: Patients typically become breathless within first 48 hours of fever onset; initially dry cough may become productive of blood-stained sputum; chest radiograph shows bilateral interstitial infiltrates 2
- Secondary bacterial pneumonia: More common than primary viral pneumonia; symptoms develop during early convalescent period or blend with initial influenza symptoms; chest radiography shows lobar pattern of consolidation 2
Complications and Outcomes
- Pneumonia can lead to respiratory failure, sepsis, and acute respiratory distress syndrome 4
- Mortality varies by pathogen and patient factors, with higher rates in primary viral pneumonia (>40%) compared to secondary bacterial pneumonia (7-24%) 2
- Pneumonia survivors often experience accelerated health decline with increased risk of cardiovascular disease 5
- Mixed viral-bacterial pneumonia carries a high mortality rate (>40%) 2
Diagnostic Approach
- Chest radiography is not recommended for routine management of uncomplicated community-acquired pneumonia in non-hospitalized patients 2
- Radiography should be considered in young children with pyrexia of unknown origin or when signs of respiratory distress are present 2
- Testing for specific pathogens like influenza and COVID-19 is recommended when these viruses are common in the community 4
Treatment Considerations
- Empirical antibacterial therapy should be selected based on disease severity, likelihood of bacterial infection, and risk of resistant infection 4
- For Mycoplasma pneumonia, macrolide antibiotics are recommended as first-line treatment 3
- Hospitalized patients without risk factors for resistant bacteria can be treated with β-lactam/macrolide combination therapy 4
- Supportive care includes ensuring adequate hydration, providing oxygen therapy if oxygen saturation is ≤92%, and using antipyretics and analgesics for symptom relief 3