An autopsy is performed on a 6-month-old girl who was born at 25 weeks gestation and died of respiratory complications. A sample of the patient's lung tissue is obtained, and histopathologic examination shows few, dilated alveoli with decreased septation. Alveolar capillaries are dysmorphic, and pulmonary arterioles have narrow lumina with thick, muscular walls. These findings are most consistent with which of the following conditions?
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This infant's autopsy findings are consistent with bronchopulmonary dysplasia (BPD), or chronic lung disease of prematurity. The pathologic findings of BPD have evolved over time as advanced treatment modalities (eg, surfactant, noninvasive ventilation) have improved survival rates and reduced iatrogenic lung injury (eg, airway overdistension, oxygen toxicity).
Currently, BPD is primarily characterized by disrupted fetal lung development in the early saccular stage. During this stage, which begins at 26 weeks gestation and extends until birth, terminal sacs form and undergo septation, increasing the surface area for gas exchange. This period is also critical for the development and growth of a capillary network within the septa.
Characteristic histopathologic findings of BPD currently include:
Few, dilated alveoli that have poor septation due to disrupted alveolarization. These malformed alveoli have decreased surface area for gas exchange, which manifests as respiratory distress in the neonatal period and a prolonged oxygen requirement.
Dysmorphic alveolar capillaries due to impaired vasculogenesis, contributing to persistent hypoxia. Patients may also have thickening of the muscular layer of the pulmonary arterioles, which leads to increased pulmonary vascular resistance and pulmonary hypertension.
(Choice B) Congenital cystic adenomatoid malformation (ie, congenital pulmonary airway malformation) is an anomaly of the respiratory tract in which abnormal lung tissue forms a cystic mass. Histopathologic examination would likely show cystic areas (lined by ciliated columnar epithelium) surrounded by relatively normal alveoli.
(Choice C) Neonatal pneumonia is most commonly bacterial, and a predominance of inflammatory cells with neutrophils within the alveoli would be seen on histopathologic examination.
(Choice D) Cystic fibrosis is caused by a defective chloride channel that allows viscous secretions to accumulate in the airways, predisposing patients to chronic inflammation and bronchiectasis. Thickened, dilated bronchi with mucus plugging would be seen.
(Choice E) Pulmonary alveolar proteinosis is characterized by surfactant accumulation within the alveoli due to impaired clearance by alveolar macrophages. Histopathologic findings would include granular, proteinaceous material within the alveoli with normal alveolar architecture.
Educational objective:
Bronchopulmonary dysplasia is common in premature infants due to arrest of fetal lung development in the saccular stage. Histopathologic examination of lung tissue shows impaired alveolarization (ie, dilated alveoli with decreased septation) and abnormal vasculogenesis (ie, dysmorphic alveolar capillaries).