Pneumonia - Community-Acquired (Pediatric)

Definition

Community-acquired pneumonia (CAP) in children is an acute infection of the lung parenchyma acquired outside a hospital setting, caused by bacteria, viruses, or atypical pathogens, leading to respiratory symptoms and systemic manifestations.

Epidemiology

• Leading cause of morbidity and mortality in children under 5 years globally
• Incidence higher in low- and middle-income countries
• Peak incidence in children <2 years
• Viral causes more common in infants and toddlers; bacterial causes increase with age
• Seasonal peaks often occur in winter and early spring

Etiology

• Bacterial: Streptococcus pneumoniae, Haemophilus influenzae type b, Staphylococcus aureus, Moraxella catarrhalis
• Viral: RSV, influenza virus, adenovirus, parainfluenza, human metapneumovirus
• Atypical bacteria: Mycoplasma pneumoniae, Chlamydophila pneumoniae
• Risk factors: malnutrition, immunodeficiency, chronic lung disease, congenital heart disease, exposure to smoke

Pathophysiology

• Pathogen inhalation or aspiration leads to alveolar infection and inflammation
• Recruitment of neutrophils and inflammatory mediators into alveoli
• Alveolar exudate causes impaired gas exchange, hypoxia, and consolidation
• Bronchial inflammation contributes to cough and airway obstruction
• Systemic inflammatory response may lead to fever, malaise, and tachycardia
• Severe cases may progress to respiratory distress or sepsis