Bronchiolitis is a major cause of hospitalization among infants. Severe bronchiolitis is associated with
later asthma, suggesting a common genetic predisposition. Genetic background of bronchiolitis is not
well characterized. To identify polymorphisms associated with bronchiolitis, we conducted a genomewide
association study (GWAS) in which 5,300,000 single nucleotide polymorphisms (SNPs) were tested
for association in a Finnish–Swedish population of 217 children hospitalized for bronchiolitis and 778
controls. The most promising SNPs (n = 77) were genotyped in a Dutch replication population of 416
cases and 432 controls. Finally, we used a set of 202 Finnish bronchiolitis cases to further investigate
candidate SNPs. We did not detect genome-wide significant associations, but several suggestive
association signals (p < 10−5) were observed in the GWAS. In the replication population, three SNPs
were nominally associated (p < 0.05). Of them, rs269094 was an expression quantitative trait locus
(eQTL) for KCND3, previously shown to be associated with occupational asthma. In the additional
set of Finnish cases, the association for another SNP (rs9591920) within a noncoding RNA locus was
further strengthened. Our results provide a first genome-wide examination of the genetics underlying
bronchiolitis. These preliminary findings require further validation in a larger sample size.