Primary Ciliary Dyskinesia (PCD): A genetic disorder of motile cilia.

Primary ciliary dyskinesia (PCD) is a genetic disorder of motile cilia. Clinical features include chronic oto-sinopulmonary disease, laterality defects, and male fertility reflecting impaired function of respiratory cilia in the upper and lower respiratory tracts, nodal cilia in the embryonic node and sperm tails, respectively. Recent studies have identified over 40 PCD-associated genes that encode proteins involved in ciliary biogenesis, assembly, structure, or function. Mutations in these genes account for approximately 70% of PCD cases; therefore, further gene discovery is expected. The diagnosis of PCD is challenging because no single test has the required diagnostic accuracy. Recent efforts have focused on standardizing and validating a panel of tests (including assessment for key clinical features, nasal nitric oxide measurement, ciliary ultrastructure analysis, and PCD genetic testing) to be used at PCD Centers to accurately diagnose PCD. Multi-center research programs focused on PCD in North America and Europe have been crucial for PCD gene discovery, advancing our understanding of the natural history of PCD and launching multi-center clinical trials.