There is increasing evidence that pulmonary inflammation contributes to the pathogenesis of chronic lung disease (CLD).¹ Cytokines are key factors in the inflammatory response. The response of various cytokines to stressful stimuli have been shown to be partly due to interindividual variation at a genetic level.² The possibility that genetic factors play a role in susceptibility to CLD has been reported.^3,4 We decided to investigate whether gene polymorphisms for tumour necrosis factor α (TNFα-308 G/A) and interleukin 1 (IL1) influence the risk of developing CLD in small preterm (<30 weeks gestation) infants. A total of 224 ventilated small preterm infants were enrolled into a case-control study to investigate the association between TNFα-308 G/A and IL1 polymorphisms in ventilated, small preterm infants with CLD. CLD was defined as dependence on active respiratory support or oxygen supplementation at 36 weeks postconceptional age. Typing of the genotype polymorphisms was performed by polymerase chain reaction and restriction analysis. Genotype distribution and allelic frequencies were compared between infants with CLD and those without CLD. According to the definition of CLD, 112 infants developed CLD, and 112 infants did not. The following clinical risk factors for CLD did not differ between the groups: prenatal steroid use, premature rupture of the membranes, presence of amnionitis, Apgar score, sex, gestational age, birth weight, surfactant therapy, patent ductus arteriosus, and sepsis.

There was no significant association between the genotype or the allelic frequency of the TNFα or IL1β exon5 or IL1 receptor antagonist (IL1RA) polymorphism with CLD and the duration of intermittent mandatory ventilation supplement. The most common genotypes for TNFα-308 polymorphism for CLD and their healthy control infants were the G homozygote. The proportions of A homozygote/G heterozygote for the TNFα-308 polymorphism for CLD and their healthy controls were 5.4/21.4/73.2% and 5.4/32.1/62.5% respectively. The most common genotypes for IL1RA for CLD and their healthy controls were the I/I homozygote. The proportions of I homozygote/II heterozygote for IL1RA for CLD and their healthy controls were 87.5/12.5% and 85.7/14.3% respectively. The most common genotypes for IL1β exon 5 for CLD and their healthy controls were the E1 homozygote. The proportions of E1 homozygote/E2 heterozygote for IL1β exon 5 for CLD and their healthy controls were 92.9/7.1% and 94.6/5.4% respectively. We conclude that TNFα-308, IL1RA, and IL1β exon 5 polymorphisms are not useful markers for predicting the susceptibility of the Chinese population in Taiwan to CLD.