Pneumonia in Children

Definition and Epidemiology

Inflammation of lung parenchyma.
Leading infectious cause of death globally in children <5 years.
Mortality closely linked to poverty; >99% of deaths in low- and middle-income countries.
Incidence decline attributed to antibiotics and vaccines (measles, pertussis, Haemophilus influenzae type b [Hib], pneumococcal conjugate vaccine [PCV]).

Pathogenesis

Disruption of complex lower respiratory ecosystem.
Pathogen entry via droplet infection.
Viral: Infection spreads along respiratory epithelium $\to$ airway obstruction from swelling, abnormal secretions, cellular debris.
Bacterial: Multiplication in alveoli $\to$ inflammatory exudate $\to$ consolidation of alveoli or infiltration of interstitial tissue.

Anatomical Classification

Lobar pneumonia.
Lobular pneumonia (bronchopneumonia).
Interstitial pneumonia.

Etiology

Age-Specific Pathogens

Age Group	Frequent Pathogens
Neonates (<3 wk)	Group B Streptococcus, Escherichia coli, Gram-negative bacilli, Streptococcus pneumoniae, H. influenzae.
3 wk to 3 mo	Respiratory syncytial virus (RSV), Rhinoviruses, Parainfluenza, S. pneumoniae, H. influenzae, Chlamydia trachomatis.
4 mo to 4 yr	RSV, Rhinoviruses, Parainfluenza, Adenovirus, S. pneumoniae, H. influenzae, Mycoplasma pneumoniae, Group A Streptococcus (GAS).
$\geq$ 5 yr	M. pneumoniae, S. pneumoniae, Chlamydophila pneumoniae, H. influenzae, Influenza, COVID-19, Legionella pneumophila.

Exposure-Specific Pathogens

Exposure History	Suspected Agent
School dormitory/household outbreak	M. pneumoniae, Neisseria meningitidis.
Contaminated aerosols (air coolers)	Legionella species.
Goat hair, raw wool, animal hides	Bacillus anthracis (Anthrax).
Bird contact	Chlamydophila psittaci.
Unpasteurized milk ingestion	Brucellosis.

Clinical Features

General Presentation

Prodrome: Upper respiratory tract infection, rhinitis, cough.
Tachypnea: Most consistent clinical manifestation.
Respiratory Distress: Intercostal/subcostal/suprasternal retractions, nasal flaring, accessory muscle use, grunting.
Auscultation: Crackles, wheezing, bronchial breathing, diminished air entry.
Severe signs: Cyanosis, lethargy, tachycardia, hypoxemia.
Abdominal pain: Referred pain from lower lobe involvement.

WHO Criteria for Tachypnea

Age Group	Respiratory Rate Cut-off
<2 months	$\geq$ 60 breaths/minute.
2 months to 1 year	$\geq$ 50 breaths/minute.
1 year to 5 years	$\geq$ 40 breaths/minute.
>5 years	$\geq$ 30 breaths/minute.

Differentiating Pneumonia Syndromes

Feature	Viral Pneumonia	Bacterial (Typical)	Atypical Pneumonia
Onset	Gradual, follows short URTI.	Sudden, rapid progression.	Gradual.
Fever	Low-grade.	High-grade.	Low-grade.
Toxicity	Less toxic.	Highly toxic.	Non-toxic (“walking pneumonia”).
Auscultation	Bilateral crackles, wheezing.	Localized crackles, bronchial breathing.	Diffuse crackles, wheezing.
X-ray	Hyperinflation, bilateral interstitial infiltrates.	Lobar consolidation.	Diffuse lung involvement, bilateral perihilar streaks.

Differential Diagnosis: Recurrent Pneumonia

Definition: $\geq$ 2 episodes/year or $\geq$ 3 episodes ever, with radiographic clearing between episodes.

Hereditary: Cystic fibrosis, Sickle cell disease.
Immunodeficiency: HIV/AIDS, Bruton agammaglobulinemia, Chronic granulomatous disease, SCID.
Ciliary Disorders: Primary ciliary dyskinesia, Kartagener syndrome.
Anatomic Disorders: Pulmonary sequestration, Congenital pulmonary airway malformation (CPAM), Bronchiectasis, Tracheoesophageal fistula.
Acquired: Foreign body aspiration, Gastroesophageal reflux.

Investigations

Laboratory

Complete Blood Count (CBC): Viral $\to$ WBC normal/elevated $\leq$ 20,000/mm³, lymphocyte predominance. Bacterial $\to$ WBC 15,000-40,000/mm³, polymorphonuclear predominance.
Biomarkers: C-reactive protein (CRP), Procalcitonin, ESR elevated in bacterial etiology.
Blood Culture: Indicated for hospitalized, toxic children, or complicated pneumonia; positive in ~10% of pneumococcal cases.
Pathogen-specific tests: Multiplex RT-PCR for viruses; Serology/PCR for Mycoplasma.

Imaging

Chest Radiograph (CXR): Identifies consolidation, atelectasis, hyperinflation, effusions. Pneumatoceles suggest Staphylococcus or Klebsiella. Routine CXR not required for uncomplicated outpatient cases.
Chest Ultrasound: Highly sensitive/specific point-of-care tool. Identifies consolidations, B-lines, air bronchograms, pleural effusions.
Chest CT: Superior for identifying early abnormalities, necrosis, abscesses, or underlying anatomical defects.

Management

Indications for Hospitalization

Age <6 months.
Hypoxemia (SpO2 <90%-92% on room air).
Toxic appearance, severe respiratory distress (grunting, cyanosis, apnea).
Inability to tolerate oral fluids/medications, severe dehydration.
Complicated pneumonia (effusion, empyema, abscess).
Failure of outpatient therapy within 48-72 hours.

Pharmacotherapy: Outpatient (Oral Therapy)

Age	First-Line	Second-Line / Alternatives
<3 months	Admit to hospital.	Admit to hospital.
3 mo to 5 yr	Amoxicillin (40-50 mg/kg/day BD in India; 80-90 mg/kg/day if high resistance).	Co-amoxiclav OR Cefpodoxime OR Cefuroxime.
>5 yr	Amoxicillin.	Macrolides (Azithromycin 10 mg/kg/day OD) for atypical organisms.

Pharmacotherapy: Inpatient (Parenteral Therapy)

Age	First-Line	Suspected S. aureus
<3 months	Cefotaxime $\pm$ Gentamicin/Amikacin OR Ceftriaxone.	Ceftriaxone + Cloxacillin OR Vancomycin/Linezolid.
3 mo to 5 yr	Ampicillin OR Ceftriaxone OR Cefotaxime.	Ceftriaxone + Cloxacillin OR Vancomycin/Clindamycin.
>5 yr	Ampicillin OR Ceftriaxone OR Macrolide.	Ceftriaxone + Cloxacillin OR Vancomycin/Clindamycin.

Note: Transition to oral antibiotics upon clinical improvement (afebrile for 48-72 hours). Total duration: 7-10 days for uncomplicated cases.

Supportive Care

Oxygen therapy to maintain SpO2 >94%.
Intravenous fluids for severe distress/dehydration.
Antipyretics (Paracetamol) for fever/comfort.
Bubble CPAP, high-flow nasal cannula (HFNC), or mechanical ventilation for impending respiratory failure.

Complications

Local/Intrathoracic: Pleural effusion, empyema, pyopneumothorax, pneumatocele, lung abscess, necrotizing pneumonia, bronchopleural fistula.
Systemic/Metastatic: Bacteremia, sepsis, purulent pericarditis, meningitis, suppurative arthritis, osteomyelitis.

Prevention

Immunization: PCV (Pneumococcal conjugate vaccine), Hib vaccine, Influenza vaccine, Measles vaccine, Pertussis vaccine.
Prophylaxis: Nirsevimab (RSV monoclonal antibody) for high-risk infants.
Environmental & Nutritional: Promotion of exclusive breastfeeding, avoidance of passive smoking, prevention of household crowding, Zinc supplementation.

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