• Uncommon aberrations of respiratory tract development
-Starts at 4th week of fetal life
-Initial phase of airway branching until 16th wk
-Canalicular phase: Capillaries develop (16th to 26th wk)
-Alveolar phase: 26th wk on, alveolar air sacs form with type I, II pneumocytes
• Tracheobronchial atresia (TA)
-Can occur at any level
-May involve isolated or multiple areas
-Diffuse disease is fatal
-Isolated bronchial atresia results in bronchus with blind pouch leads to compression of surrounding lung and emphysematous changes
-Anomalous tracheal or esophageal bronchi and diverticular are related diseases
• Bronchogenic cysts (BC)
-Abnormal budding of foregut may result in formation of BC
-Commonly occur in pulmonary hilum or mediastinum, occasionally pulmonary parenchyma
-Usually single, lined by cuboidal respiratory epithelium, preferentially in lower lobes
-Cysts generally thin walled, occasionally with cartilage
-May communicate with tracheobronchial tree
-Known to enlarge rapidly and rupture causing tension pneumothorax
• Bronchopulmonary dysplasia (BPD): Cluster of diseases includes pulmonary agenesis, aplasia, and primary and secondary hypoplasia
-Unilateral agenesis occurs when 1 lung and vessels fail to develop
-Pulmonary aplasia: Blind bronchial tumor stump exists and soils normal lung with secretions
-Pulmonary hypoplasia: Low radial alvelolar count and low lung to body weight ratio without inciting cause
-Secondary pulmonary hypoplasia: Occurs due to fetal or maternal abnormalities such as congenital diaphragmatic hernia, oligohydramnios, Potter syndrome, abnormal bone development
• Pulmonary sequestration (PS)
-Abnormal budding of foregut leading to lung parenchyma without bronchial communication
-Can be intralobar (85%) or extralobar
-Often have systemic blood supply from abdominal aorta, 96% drain into pulmonary venous system
• Cystic adenomatoid malformation (CAM)
-Overgrowth of terminal bronchiolar structures lined by respiratory epithelium with disorganized elastic connective tissue and smooth muscle
-Solid structures interspersed with cysts resembling immature alveoli
• Congenital Lobar Emphysema (LE)
-Hypoplastic bronchial cartilage in 25-75% of patients; increased alveoli number in 37% (polyalveoli)
-Neonates with prolonged vent support may develop LE from catheter trauma and barotraumas, affecting right lower lobe (RLL)
• BPD: 50% have associated cardiac anomalies
• PS: Left lung affected 58% of time
• LE: Left upper lobe (LUL) most commonly involved, then right middle lobe (RML)
• Often presents early in life
• Some remain occult until adulthood
• TA: Neonates present with intractable cyanosis with normal larynx on intubation
• Isolated bronchial atresia: Wheezing, stridor, pulmonary infections due to mucocele formation and compression of normal lung
• BC: Mediastinal present with airway compression, parenchymal present with pulmonary infection
• BPD (agenesis): Neonates present with tachypnea and cyanosis
• BPD: Some patients present in childhood; dyspnea and wheezing and tracheal deviation toward side of agenesis
• BPD (hypoplasia): Presents in neonates with tachypnea and hypoxemia resistant to oxygen; persistent fetal circulation
• PS: Presentation ranges from asymptomatic lower lobe masses to recurrent lower lobe infections due to seeding from pores connected to normal lung, rarely hemoptysis, congestive heart failure due ...
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