First reported CABP2-related non-syndromic hearing loss in Northern Europe

Background: CABP2-related non-syndromic hearing loss have only been reported in a few families worldwide (Iran, Turkey, Pakistan and Italy). The hearing loss was in these cases described as prelingual, symmetrical, and moderate to severe. Methods: Following DNA isolation, exome sequencing was performed in 123 genes related to non-syndromic hearing loss. Variant verification and carrier testing were performed by direct sequencing. Results: We report the first Northern European individual with CABP2-related hearing loss: an 8-year-old Danish Caucasian boy with non-syndromic, prelingual, and sensorineural hearing loss, who is homozygous for the splice site variant CABP2: c. 637+1G>T previously found in three Iranian families and in one Pakistani family. Both parents are of Danish Caucasian origin with no known history of consanguinity. This is in contrast to the four reported Middle Eastern families, who all were consanguineous. However, loss of heterozygosity in a 3.2 Mb area on chromosome 11 including CABP2 was observed, suggesting a common parental ancestor. Conclusion: We report the first case of CABP2-related autosomal recessive hearing loss in Northern Europe. The index is of Danish Caucasian origin and found to be homozygous for the splice site variant c.637+1G>T.