What are the differential diagnoses for a child less than 5 years of age presenting with respiratory distress?

Differential Diagnoses for Respiratory Distress in Children Under 5 Years

The differential diagnosis for respiratory distress in children under 5 years should be systematically categorized into five major groups: upper airway obstruction, pneumonia syndrome, lower airway obstruction, central/neuromuscular causes, and cardiac causes, with pneumonia and bronchiolitis being the most common etiologies in this age group. 1, 2, 3

Clinical Recognition of Respiratory Distress

Before considering differentials, recognize respiratory distress by these specific signs:

• Tachypnea: Age-specific thresholds are critical: 0-2 months >60 breaths/min, 2-12 months >50 breaths/min, 1-5 years >40 breaths/min 1, 4
• Increased work of breathing: Retractions (suprasternal, subcostal, intercostal), nasal flaring, use of accessory muscles 1
• Grunting: This is a sign of severe disease and impending respiratory failure with a positive likelihood ratio of 2.7 for serious pulmonary pathology 1, 2
• Hypoxemia: SpO2 <92% at sea level (or <90% in some guidelines) 1, 2
• Altered mental status: Due to hypercarbia or hypoxemia 1

Category 1: Upper Airway Obstruction

Anatomic Causes

• Choanal atresia: Presents with unilateral or bilateral nasal obstruction; particularly critical in infants under 2-6 months who are obligate nasal breathers 4
• Laryngomalacia/tracheomalacia: Diagnosed via flexible bronchoscopy 1
• Subglottic stenosis: May prevent extubation in mechanically ventilated infants 1
• Foreign body aspiration: Consider in sudden onset respiratory distress 3

Infectious/Inflammatory Causes

• Croup (laryngotracheobronchitis): Barking cough, stridor 3
• Epiglottitis: Toxic appearance, drooling, tripod positioning 3
• Retropharyngeal abscess: Fever, neck stiffness, muffled voice 3

Category 2: Pneumonia Syndrome (Cough, Fever, Breathing Difficulty)

Pneumonia is the most likely diagnosis when grunting accompanies fever, tachypnea, and respiratory distress in children under 5 years. 2

Bacterial Pneumonia

• Community-acquired pneumonia (CAP): Can be simple (single lobe) or complicated (multilobar, effusions, empyema, necrotizing) 1
• CA-MRSA pneumonia: Increased virulence pathogen requiring hospitalization 1
• Mixed bacterial-viral infections: Higher rates of mechanical ventilation (8.3%) and mortality (5.6%) 1

Viral Pneumonia

• Bronchiolitis: Most common in infants <6 months, presents with preceding URI symptoms, wheezing, crackles; grunting indicates moderate-to-severe disease 2
• RSV, influenza, rhinovirus, adenovirus: Children with concurrent viral and invasive pneumococcal infection have longer ICU stays 1

Risk Factors to Identify

• Prematurity, malnutrition, HIV exposure, immunodeficiency 2
• Age <3-6 months with suspected bacterial infection warrants hospitalization 1, 5

Category 3: Lower Airway Obstruction

Obstructive Diseases

• Asthma exacerbation: Wheezing, prolonged expiration, response to bronchodilators 3
• Bronchiolitis: Viral lower respiratory tract infection with wheezing and crackles 2

Aspiration Syndromes

• Meconium aspiration syndrome: In newborns with meconium-stained amniotic fluid 6, 7
• Milk aspiration/laryngopharyngeal reflux: Choking during feeds, apneic spells, recurrent pneumonia 4
• Foreign body aspiration: Sudden onset, unilateral findings 3

Category 4: Central/Neuromuscular Causes (Slow or Irregular Breathing Without Pulmonary Signs)

• Neuromuscular diseases: Spinal muscular atrophy, muscular dystrophy causing restrictive lung disease 8
• Central nervous system depression: Sepsis, meningitis, metabolic disorders 3
• Primary ciliary dyskinesia: Recurrent rhinitis, neonatal respiratory distress (80% of cases), situs inversus (40-55%), chronic wet cough from early childhood 1

Category 5: Cardiac Causes (Respiratory Distress with Cardiac Findings)

• Congenital heart defects: Critical congenital heart disease should be screened via pulse oximetry after 24 hours but before discharge 6
• Heart failure: Tachycardia, hepatomegaly, poor perfusion 3
• Persistent pulmonary hypertension of the newborn: Severe hypoxemia disproportionate to lung disease 6

Age-Specific Considerations

Neonates and Young Infants (<3-6 months)

• Transient tachypnea of the newborn: Self-limited, typically resolves within 24-72 hours 6, 7
• Respiratory distress syndrome (RDS): Prematurity, surfactant deficiency 6, 7
• Neonatal sepsis/pneumonia: Group B streptococcus, E. coli 6, 7
• Neonatal respiratory distress in PCD: 80% of PCD patients have history of neonatal respiratory distress as term newborns requiring supplemental oxygen or positive pressure ventilation >24 hours 1

Infants and Children (6 months to 5 years)

• Pneumonia: Bacterial (S. pneumoniae, CA-MRSA) or viral (RSV, influenza) 1
• Bronchiolitis: Peak incidence in infants <12 months 2
• Asthma: Can present as early as 1-2 years 3

Critical Pitfalls to Avoid

• Do not dismiss grunting: It indicates severe disease and impending respiratory failure requiring immediate hospitalization 1, 2
• Do not rely solely on severity scores: Clinical appearance and behavior predict severity as much as any score; use scores in context with clinical findings 1
• Do not overlook anatomic causes in young infants: Nasal passages contribute 50% of total airway resistance in newborns; even minor obstruction can cause near-total blockage 4
• Do not miss aspiration: Look for symptoms during/after feeds, history of choking, apneic spells, recurrent pneumonia 4
• Do not forget cardiac screening: All newborns should be screened for critical congenital heart defects before discharge 6
• Consider PCD in children with: Year-round daily wet cough and rhinosinusitis from early childhood, neonatal respiratory distress as term infant, laterality defects, chronic otitis media requiring tubes before age 5 1

Immediate Diagnostic Approach

1. Measure oxygen saturation immediately: SpO2 <90-92% mandates supplemental oxygen and hospitalization 1, 2, 5
2. Assess work of breathing: Retractions, nasal flaring, grunting indicate severity 1, 4
3. Obtain chest radiography: Helpful in differentiating pneumonia, pneumothorax, cardiac causes 6
4. Consider blood cultures: In children requiring hospitalization for presumed bacterial pneumonia, particularly if complicated 5
5. Arterial blood gas if severe: PaO2/FiO2 ratio indicates degree of respiratory insufficiency 1