Among all genetic mutations, nearly 15–20% of all PCD patients results from mutations within Dynein Axonemal Heavy Chain 5 (DNAH5) gene (MIM: 603335) [10, 27] causing outer dynein arm (ODA) defects [14]; DNAH5 and Dynein Axonemal Intermediate Chain 1 (DNAI1) mutations are the most frequent mutations encountered in correlation with ODA defects, ~ 50% and ~ 10% of cases, respectively [23]; mutations in other genes are much less frequent. The gene discussed is DNAI1; the disease is primary ciliary dyskinesia.