Polymorphisms of surfactant protein B encoding gene: modifiers of the course of neonatal respiratory distress syndrome?

Abstract

Surfactant protein B (SP-B) is a lipophilic protein and plays a major role in lung mechanics. Polymorphisms of surfactant protein A, another component of the surfactant system, have been previously described to be a risk factor for respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD) in preterms. The aim of this prospective study was to determine whether polymorphisms within intron 4 of the SP-B gene are related to the incidence, severity and complications of RDS in Caucasian newborns. In order to identify SP-B intron 4 polymorphisms, we analysed genomic DNA by means of polymerase chain reaction, fragment length and sequence analysis in 140 preterms and 58 healthy term neonates. The frequency of intron 4 variations did not differ between preterms and terms. A total of 111 preterms with the intron 4 wild type (group 1) and 29 preterms carrying the genetic variations (group 2) did not differ in gestational age, gender distribution and birth weight. Compared to group 1, the overall incidence of RDS (75.7% versus 93.1%, P < 0.05), the frequency of severe RDS (28.4% versus 55.2%, P < 0.01) and BPD (21.6% versus 48.3%, P < 0.01) were all higher in group 2. The median duration of oxygen dependency (4 days versus 17 days, P < 0.05) and the need for surfactant administration were also higher in group 2 than in group 1 (43.2% versus 72.4%, P < 0.01). Duration of mechanical ventilation and rate of chronic lung disease at 36 weeks were comparable in both groups. we suggest that polymorphisms in intron 4 of the surfactant protein B gene independently modify the course of neonatal respiratory distress syndrome.