Genetic susceptibility to otitis media in childhood

Otitis media (OM) is a common disease in early childhood characterized by inflammation of the middle ear cavity. Heritability studies suggest that there is a substantial genetic component (40%-70%) to the risk of recurrent acute OM, defined as three or more episodes in 6 months or four or more episodes in a year, or chronic OM with effusion (COME), defined as middle ear fluid for ≥ 3 months. To date, only a handful of the regions/genes underlying this genetic susceptibility have been identified. These include several regions of linkage on chromosome 3p25, 10q22, 10q26, 17q12, and 19q13 identified by two genome-wide linkage scans, which appear to harbor susceptibility loci. Fine mapping of these regions has yet to identify the causative genes. Several candidate genes studies have also been reported, with candidates selected on the basis of a plausible biological role in OM or through OM mouse models. Reviewed in this article, these studies have identified positive association at 21 genes, including FBXO11, TLR4, and TNF, with association at five of these replicated in independent populations. However, these studies have been based on small sample sizes, and it is only recently that well-powered OM cohorts suitable for genome-wide association studies (GWAS) have become available. Results from such GWAS will identify novel genes involved in this complex disease. Identification of the genes that contribute to OM susceptibility in childhood will provide important insights into the biological complexity of this disease that could ultimately contribute to improved preventative and therapeutic strategies to reduce the incidence of this disease.