Primary ciliary dyskinesia (PCD [MIM 244400])4,5 refers to an autosomal-recessive inherited disorder in which structure and assembly of motile cilia and sperm is deficient, often accompanied by visible ultrastructural defects, resulting in dysmotile or static axonemes. PCD is characterized by lifelong recurrent respiratory infections and irreversible, destructive airway disease (bronchiectasis) of early onset. Otitis media and nasal polyps are common and male infertility may occur, as well as laterality defects affecting approximately half of affected individuals, with around 12% manifesting as complex isomerisms and heterotaxies usually associated with congenital heart defects.6,7 Distinct from ultrastructural ciliary defects, CCNO (MIM 607702) mutations have recently been identified to cause a mucociliary clearance disorder related to, but distinct from, PCD that was previously called ciliary aplasia but is now termed RGMC (reduced generation of multiple motile cilia), because in RGMC a few motile cilia are still detectable at the cell surface.8