Genetic analysis reveals that mutations in EYA1 (Buller et al., 2001; Chang et al., 2004; Johnson et al., 1999; Kalatzis et al., 1998; Li et al., 2018; Musharraf et al., 2014; Orten et al., 2008; Wang et al., 2018), SIX1 (Kochhar et al., 2008; Ruf et al., 2004; Shah et al., 2020) and SIX5 (Hoskins et al., 2007) cause BOR syndrome, an autosomal dominant developmental defect characterised by branchial and external ear malformations, hearing loss and renal anomalies (Abdelhak et al., 1997; Fraser et al., 1980; Sanggaard et al., 2007). Here, SIX5 is linked to BOR syndrome.