Knockout of the dynein axonemal heavy chain 5 (Dnah5) gene, one of the most frequently mutated genes in human PCD, was found to result in rapid progression of hydrocephalus in mice, leading to death within approximately one month [13,14]; however, no clear association between Dnah5 and the onset of hydrocephalus in humans has been established to date. Here, DNAH5 is linked to primary ciliary dyskinesia.