In contrast to evident structural alterations in the cilia of PCD patients carrying mutations in either CCDC39 or CCDC40 genes or gene encoding proteins indispensable for the assembly of the functional ODAs, cilia in individuals with PCD caused by the mutation in genes encoding N-DRC subunits at first glance have normal or nearly normal structure [154,155,160]. Here, CCDC39 is linked to primary ciliary dyskinesia.