DNAH9 and primary ciliary dyskinesia: Biallelic mutations in DNAH9 cause PCD with a frequent loss of ODAs at the distal, but not the proximal, regions of cilia (Fassad et al., 2018; Loges et al., 2018), and the patient carrying two homozygous missense mutations in DNAH9 presented with oligoasthenoteratozoospermia (Fassad et al., 2018), yet the underlying ultrastructural anomalies and pathogenic mechanism remain unknown.