Frequency of allelic variants of the surfactant protein B (SP-B) GENE in patients with acute respiratory distress syndrome (ARDS)

Introduction: Intron 4 of the human SP-B gene consists of a polymorphic region, derived by insertion or deletion of copies of a motif, consisting of a 20 base pair conserved fragment and a variable number of dinucleotide repeats (CA_n). The frequency of variant alleles due to this insertion/deletion has been associated with respiratory distress syndrome (RDS). We studied the frequency of variant alleles due to this polymorphism in 15 patients with ARDS and 23 healthy control individuals. Methods: A fragment of intron 4 of the SP-B gene was amplified from genomic DNA using polymerase chain reaction (PCR) with radiolabelled oligonucleotides. Following amplification, the fragments were analysed for differences in length, using polyacrylamide gel elctrophoresis. Results: The frequency of variant alleles of the SP-B gene was significantly higher in patients with ARDS (46.6%) compared to healthy control individuals (4.3%). No coincidence between survival of ARDS and the frequency of variant alleges was found. The biological relevance of this finding, if any, remains unclear.