Author
June Hu, M.D. 1, Frances White, M.D. 2, F.S. Cole, M.D. 1, Jennifer Wambach, M.D., M.S. 1
1 Edward Mallinckrodt Department of Pediatrics,
Washington University School of Medicine, St. Louis, Missouri, United States 63110
2 Department of Pathology and Immunology,
Washington University School of Medicine, St. Louis, Missouri, United States 63110
Case
A term female infant, born of an uncomplicated pregnancy to a 20-year-old primigravida mother via cesarean section, developed respiratory distress immediately after birth requiring intubation and mechanical ventilation. Her initial chest radiograph was consistent with hyaline membrane disease and she was treated with two doses of surfactant within 48 hours after birth with transient improvement. She continued to have persistent hypoxemic respiratory failure despite escalating care which included conventional mechanical ventilation, high-frequency oscillatory ventilation and inhaled nitric oxide. On day 9 of life, computed tomography of the chest demonstrated diffuse ground glass opacities. A comprehensive infectious disease workup was negative. She was unresponsive to steroid therapy including dexamethasone (0.15 mg/kg/day for 10 days) and three courses of methylprednisolone (30 mg/kg/day for 3 days). Open lung biopsy performed at day of life 15 demonstrated interstitial lung disease with pneumocyte hyperplasia and alveolar proteinosis (figure 1). Immunohistochemical staining demonstrated aberrant surfactant expression. Electron microscopy demonstrated abnormal appearing lamellar bodies (figure 2). Genetic testing for disorders of surfactant metabolism was sent. She was treated with exogenous surfactant every 12-48 hours prior to referral for evaluation for lung transplantation.
Question
Which of the following disrupts phospholipid transport into lamellar bodies where surfactant is assembled, and is the most common genetic cause of disruption of surfactant metabolism?
A. Surfactant protein B deficiency
B. ABCA3 deficiency
C. Mutations in the surfactant protein C gene
D. Mutations in NKX2-1 which encodes thyroid transcription factor 1
E. None of the above