Primary ciliary dyskinesia (PCD) is an inherited autosomal-recessive disorder of motile cilia characterised by chronic lung disease, rhinosinusitis, hearing impairment and subfertility. Nasal symptoms and respiratory distress usually start soon after birth, and by adulthood bronchiectasis is invariable. Organ laterality defects, usually situs inversus, occur in ∼50% of cases. The estimated prevalence of PCD is up to ∼1 per 10 000 births, but it is more common in populations where consanguinity is common. This review examines who to refer for diagnostic testing. It describes the limitations surrounding diagnosis using currently available techniques and considers whether recent advances to genotype patients with PCD will lead to genetic testing and screening to aid diagnosis in the near future. It discusses the challenges of monitoring and treating respiratory and ENT disease in children with PCD.

Reduced generation of multiple motile cilia (RGMC) is a rare mucociliary clearance disorder. Affected persons suffer from recurrent infections of upper and lower airways because of highly reduced numbers of multiple motile respiratory cilia. Here we report recessive loss-of-function and missense mutations in MCIDAS-encoding Multicilin, which was shown to promote the early steps of multiciliated cell differentiation in Xenopus. MCIDAS mutant respiratory epithelial cells carry only one or two cilia per cell, which lack ciliary motility-related proteins (DNAH5; CCDC39) as seen in primary ciliary dyskinesia. Consistent with this finding, FOXJ1-regulating axonemal motor protein expression is absent in respiratory cells of MCIDAS mutant individuals. CCNO, when mutated known to cause RGMC, is also absent in MCIDAS mutant respiratory cells, consistent with its downstream activity. Thus, our findings identify Multicilin as a key regulator of CCNO/FOXJ1 for human multiciliated cell differentiation, and highlight the 5q11 region containing CCNO and MCIDAS as a locus underlying RGMC.

A diverse family of cytoskeletal dynein motors powers various cellular transport systems, including axonemal dyneins generating the force for ciliary and flagellar beating essential to movement of extracellular fluids and of cells through fluid. Multisubunit outer dynein arm (ODA) motor complexes, produced and preassembled in the cytosol, are transported to the ciliary or flagellar compartment and anchored into the axonemal microtubular scaffold via the ODA docking complex (ODA-DC) system. In humans, defects in ODA assembly are the major cause of primary ciliary dyskinesia (PCD), an inherited disorder of ciliary and flagellar dysmotility characterized by chronic upper and lower respiratory infections and defects in laterality. Here, by combined high-throughput mapping and sequencing, we identified CCDC151 loss-of-function mutations in five affected individuals from three independent families whose cilia showed a complete loss of ODAs and severely impaired ciliary beating. Consistent with the laterality defects observed in these individuals, we found Ccdc151 expressed in vertebrate left-right organizers. Homozygous zebrafish ccdc151(ts272a) and mouse Ccdc151(Snbl) mutants display a spectrum of situs defects associated with complex heart defects. We demonstrate that CCDC151 encodes an axonemal coiled coil protein, mutations in which abolish assembly of CCDC151 into respiratory cilia and cause a failure in axonemal assembly of the ODA component DNAH5 and the ODA-DC-associated components CCDC114 and ARMC4. CCDC151-deficient zebrafish, planaria, and mice also display ciliary dysmotility accompanied by ODA loss. Furthermore, CCDC151 coimmunoprecipitates CCDC114 and thus appears to be a highly evolutionarily conserved ODA-DC-related protein involved in mediating assembly of both ODAs and their axonemal docking machinery onto ciliary microtubules.

Determining the prevalence of primary ciliary dyskinesia (PCD) in different populations has proved difficult with estimates varying between 1 in 4,000 to 1 in 40,000. The aim of this study was to determine the incidence of PCD in a well defined highly consanguineous Asian population in the UK.Over a fifteen year period all patients suspected of PCD in the Asian population of Bradford, UK, were tested by measurement of ciliary beat pattern, frequency and electron microscopy.The prevalence of primary ciliary dyskinesia in the population studied was 1 in 2265. 52% of the patients' parents were first cousins. All patients had a history of chronic cough and nasal symptoms from the first year of life. 73% had a history of neonatal respiratory distress.