Chronic respiratory distress with surfactant metabolism deficiency

Chronic respiratory distress with surfactant metabolism deficiency is a group of rare, severe interstitial lung diseases caused by genetic defects in the production, processing, or recycling of pulmonary surfactant. Pulmonary surfactant is a complex mixture of lipids and proteins that lines the alveoli (air sacs) of the lungs, reducing surface tension and preventing lung collapse during breathing. When surfactant metabolism is disrupted, patients develop progressive respiratory insufficiency characterized by chronic oxygen dependency, tachypnea (rapid breathing), retractions, cyanosis, and failure to thrive. Chest imaging typically reveals diffuse ground-glass opacities and interstitial changes, and lung biopsy may show patterns consistent with pulmonary alveolar proteinosis, desquamative interstitial pneumonitis, or nonspecific interstitial pneumonia. This condition can result from mutations in several genes involved in surfactant metabolism, including SFTPB (surfactant protein B deficiency), SFTPC (surfactant protein C deficiency), ABCA3 (ATP-binding cassette transporter A3 deficiency), and NKX2-1 (thyroid transcription factor 1). The inheritance pattern varies depending on the specific genetic defect: SFTPB and ABCA3 deficiencies follow autosomal recessive inheritance, while SFTPC and NKX2-1 deficiencies are typically autosomal dominant. Age of onset and severity also vary, ranging from fatal neonatal respiratory failure (particularly in SFTPB deficiency) to chronic interstitial lung disease presenting in infancy, childhood, or even adulthood. Treatment is largely supportive and may include supplemental oxygen, mechanical ventilation, exogenous surfactant replacement (though this is often of limited long-term benefit), corticosteroids, hydroxychloroquine, and azithromycin. Whole lung lavage has been used in cases with significant alveolar proteinosis. For the most severe forms, particularly complete surfactant protein B deficiency, lung transplantation remains the only definitive treatment option. Prognosis varies widely depending on the underlying genetic cause and the severity of the surfactant deficiency.

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