DNAH5 (dynein axonemal heavy chain 5) encodes a motor protein essential for ciliary motility, functioning as a component of the outer dynein arm that generates force toward microtubule minus ends through ATP hydrolysis 1. The protein is critical for coordinated beating of respiratory cilia and ependymal cilia lining brain ventricles, and is also required for normal sperm flagellar motility 2. DNAH5 mutations are a common cause of primary ciliary dyskinesia (PCD), an autosomal recessive disorder characterized by recurrent airway infections and situs inversus totalis 1. Mutations result in outer dynein arm defects visible on electron microscopy, with mutant protein mislocalizing to microtubule organizing centers rather than assembling properly in the ciliary axoneme 1. DNAH5 mutations account for approximately 9-15% of PCD cases globally, with distinct geographic founder mutations such as c.10815delT in North America and c.8030G>A in Asia 3. Clinically, patients with biallelic truncating DNAH5 variants present earlier with more severe disease, including neonatal respiratory distress and worse lung function decline compared to missense variant carriers 3. In infertile males, reduced DNAH5 expression correlates with asthenozoospermia and terato-asthenozoospermia, regulated inversely by linc02220 lncRNA 2. Notably, DNAH5 mutations are associated with better clinical outcomes than mutations in other ciliary genes like CCDC39/40 4.