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  • • 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)

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Epidemiology

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  • 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)

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Symptoms and Signs

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  • • 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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