Genetic Variability of Surfactant Protein-B and Respiratory Distress Syndrome: Clinical Implications

, Departments of Cellular and Molecular Physiology and Pediatrics; , Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pa.

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Abstract

Pulmonary surfactant, a lipoprotein complex produced by alveolar epithelial cells, is essential for normal lung function. It reduces alveolar collapse by decreasing surface tension within the alveoli. Because surfactant is produced relatively late in fetal life, the prematurely-born infant may have insufficient quantities necessary to maintain pulmonary integrity. Deficiency of surfactant can lead to onset of respiratory distress syndrome (RDS), a major cause of morbidity and mortality in the premature infant. Direct tracheal instillation of surfactant preparations have been effective in reducing disease severity. Results of a number of studies suggest that multiple factors -- both genetic and environmental -- may contribute to the etiology/pathogenesis of RDS. Because the surfactant proteins play an important role in endogenous surfactant function, alterations in the genes encoding these proteins can have a significant impact on disease course. Two of these proteins, SP-A and SP-B, are found in reduced amounts in infants who died or suffer from RDS. Therefore, the SP-A and SP-B genes seem likely candidates for investigating the impact of genetic abnormalities on the pathogenesis of RDS. In this article we review the role of surfactant in normal lung function, the consequences of surfactant deficiency on the clinical outcome of the prematurely-born infant, and the physiological role of SP-B in surfactant function. We also discuss the genetic characterization of the SP-B gene in the context of known mutations or polymorphisms and the potential impact of these genetic alterations on the SP-B protein product.

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