A 28-week male infant born to a 32-year-old primigravida with gestational diabetes is delivered by emergency cesarean section for fetal distress. Birth weight is 1.2 kg. At 2 hours of life, the infant develops progressive respiratory distress with tachypnea (68 breaths/min), intercostal retractions, grunting, and cyanosis on room air. Chest X-ray shows a diffuse ground-glass appearance with air bronchograms. Blood gas analysis reveals pH 7.20, PaCO₂ 58 mmHg, PaO₂ 45 mmHg on FiO₂ 0.60. The infant was not given antenatal corticosteroids. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Respiratory Distress Syndrome (RDS) ### Key Distinguishing Features **Key Point:** RDS (Hyaline Membrane Disease) is the most common cause of respiratory distress in preterm infants, caused by surfactant deficiency. ### Why This Case Points to RDS | Feature | RDS | TTN | MAS | Pneumonia | |---------|-----|-----|-----|----------| | **Gestation** | <37 weeks (esp <32) | ≥35 weeks | Term/post-term | Any | | **Onset** | 0–2 hours | 1–6 hours | 0–4 hours | 12–72 hours | | **CXR pattern** | Ground-glass + air bronchograms | Hyperinflation + fluid lines | Patchy infiltrates + hyperinflation | Focal infiltrates | | **Risk factors** | Prematurity, maternal DM, male sex | Maternal sedation, LSCS | Meconium-stained liquor | Chorioamnionitis, prolonged ROM | | **Surfactant** | Deficient | Normal | Normal | Normal | **Clinical Pearl:** This 28-week male infant has **classic RDS risk factors**: extreme prematurity, male sex, maternal gestational diabetes (impairs fetal lung maturation), and **no antenatal corticosteroids** (which accelerate surfactant synthesis). The **immediate onset at 2 hours**, ground-glass CXR, and **respiratory acidosis with hypoxia** are pathognomonic. ### Pathophysiology 1. Surfactant deficiency → increased alveolar surface tension 2. Alveolar collapse (atelectasis) → ventilation-perfusion mismatch 3. Hypoxemia, hypercarbia, and respiratory acidosis 4. Protein-rich fluid leaks into alveoli → hyaline membrane formation **High-Yield:** The **ground-glass appearance with air bronchograms** on CXR is the hallmark radiological finding of RDS. ### Management Principles **Key Point:** Exogenous surfactant replacement is the definitive treatment. - **Antenatal corticosteroids** (betamethasone 12 mg IM × 2 doses, 24 hours apart) reduce RDS incidence by ~50% if given between 24–34 weeks - **Postnatal surfactant therapy** (within 1–2 hours of birth): reduces mortality and air leak complications - **Respiratory support**: CPAP or mechanical ventilation depending on severity - **Supportive care**: thermoregulation, fluid/electrolyte management, glucose control **Mnemonic: SURFACTANT** — **S**urfactant replacement, **U**se antenatal steroids, **R**espiratory support (CPAP/ventilation), **F**luid management, **A**void hypothermia, **C**ontinuous monitoring, **T**emperature control, **A**ntibiotics if sepsis suspected, **N**utrition support, **T**reatment of complications. [cite:Nelson Textbook of Pediatrics 21e Ch 101]