What is the differential diagnosis for respiratory distress in a child under 5 years of age?

Differential Diagnosis of Respiratory Distress in Children Under 5 Years

Age-Specific Diagnostic Categories

In children under 5 years presenting with respiratory distress, systematically categorize the presentation into one of five major groups: upper airway obstruction, pneumonia syndrome (cough, fever, breathing difficulty), lower airway obstruction, slow/irregular breathing without pulmonary signs, or respiratory distress with cardiac findings. 1

Upper Airway Obstruction

• Croup (laryngotracheobronchitis) - presents with barking cough, inspiratory stridor, and hoarseness 1
• Epiglottitis - sudden onset with drooling, muffled voice, and toxic appearance 1
• Foreign body aspiration - sudden onset, unilateral wheeze, history of choking episode 1
• Retropharyngeal abscess - fever, neck stiffness, difficulty swallowing 1

Pneumonia Syndrome (Cough + Fever + Breathing Difficulty)

• Bacterial pneumonia - fever, tachypnea (≥70 breaths/minute indicates increased severity risk), focal crackles, chest indrawing 2, 1
• Viral pneumonia - gradual onset, bilateral findings, lower fever 1
• Aspiration pneumonia - history of vomiting, choking, or neurological impairment 1

Lower Airway Obstruction

Bronchiolitis - the most common cause in infants under 2 years, presents with tachypnea, wheezing, crackles, and respiratory distress following upper respiratory symptoms 2

• RSV accounts for 60-75% of hospitalized bronchiolitis cases 2
• Apnea occurs particularly in infants <1 month or <48 weeks postconceptional age for preterm infants 2
• Routine viral testing is NOT recommended except when determining breakthrough infection in infants receiving palivizumab prophylaxis 2

Asthma/Reactive Airway Disease

• Recurrent wheeze is the most important symptom suggesting asthma in young children 3, 4
• Diagnosis in children under 5 years relies on documented wheeze (by auscultation or reliable parental report), pattern of symptoms with triggers (viral infections, exercise, allergens), and response to bronchodilator treatment 4
• Chronic cough alone without wheeze is unlikely to be asthma and should prompt investigation for alternative diagnoses 3, 5
• Objective testing (spirometry, FeNO, peak flow) cannot be reliably performed in children under 6-7 years 3

Respiratory Distress in Neonates (First Month of Life)

Transient tachypnea of the newborn (TTN) - most common in term infants delivered by elective cesarean section, especially before 39 weeks gestation 6, 7

Respiratory distress syndrome (RDS) - inversely related to gestational age, responds to surfactant administration 7

Meconium aspiration syndrome - history of meconium-stained amniotic fluid, respiratory distress at birth 6, 7

Neonatal pneumonia - particularly Group B Streptococcus; maternal screening and intrapartum antibiotic prophylaxis are effective prevention strategies 7

Persistent pulmonary hypertension of the neonate (PPHN) - severe hypoxemia disproportionate to chest radiograph findings 6

Pneumothorax - sudden deterioration, decreased breath sounds unilaterally, requires needle thoracotomy 1, 6

Slow or Irregular Breathing Without Pulmonary Signs

• Central nervous system pathology - meningitis, encephalitis, increased intracranial pressure 1
• Metabolic disorders - hypoglycemia, electrolyte disturbances, inborn errors of metabolism 1
• Neuromuscular disorders - botulism, myasthenia gravis, spinal muscular atrophy 1
• Drug/toxin exposure - opioids, sedatives, organophosphates 1

Respiratory Distress with Cardiac Findings

• Congenital heart disease - cyanosis, heart murmur, hepatomegaly, poor perfusion 2, 1
• Congestive heart failure - tachycardia, gallop rhythm, cardiomegaly on chest radiograph 1
• Myocarditis - preceding viral illness, muffled heart sounds, arrhythmias 1

Critical Assessment Parameters

Respiratory rate thresholds: Normal 50th percentile decreases from 41 breaths/minute at 0-3 months to 31 breaths/minute at 12-18 months; tachypnea ≥70 breaths/minute indicates increased severity risk 2

Pulse oximetry: Oxygen saturation <95% on room air among outpatients may predict disease progression, though evidence differs on predictive value for mild reductions 2

Physical examination findings: Nasal flaring, chest retractions (subcostal, intercostal, suprasternal), grunting, cyanosis 1, 7

Critical Pitfalls to Avoid

• Do NOT diagnose asthma based on breathing difficulty or cough alone - these symptoms are highly nonspecific 4
• Do NOT use vague labels like "reactive airway disease" or "wheezy bronchitis" to avoid proper diagnostic evaluation 5
• Do NOT perform routine viral testing for bronchiolitis except in specific circumstances (palivizumab recipients) 2
• Do NOT rely on allergy testing to diagnose asthma - it may identify triggers but has low specificity for diagnosis 3