Primary ciliary dyskinesia (PCD) is a genetically heterogeneous recessive disorder characterized by defective cilia and flagella motility. Chronic destructive-airway disease is caused by abnormal respiratory-tract mucociliary clearance. Abnormal propulsion of sperm flagella contributes to male infertility. Genetic defects in most individuals affected by PCD cause randomization of left-right body asymmetry; approximately half show situs inversus or situs ambiguous. Almost 70 years after the hy3 mouse possessing Hydin mutations was described as a recessive hydrocephalus model, we report HYDIN mutations in PCD-affected persons without hydrocephalus. By homozygosity mapping, we identified a PCD-associated locus, chromosomal region 16q21-q23, which contains HYDIN. However, a nearly identical 360 kb paralogous segment (HYDIN2) in chromosomal region 1q21.1 complicated mutational analysis. In three affected German siblings linked to HYDIN, we identified homozygous c.3985G>T mutations that affect an evolutionary conserved splice acceptor site and that subsequently cause aberrantly spliced transcripts predicting premature protein termination in respiratory cells. Parallel whole-exome sequencing identified a homozygous nonsense HYDIN mutation, c.922A>T (p.Lys307(∗)), in six individuals from three Faroe Island PCD-affected families that all carried an 8.8 Mb shared haplotype across HYDIN, indicating an ancestral founder mutation in this isolated population. We demonstrate by electron microscopy tomography that, consistent with the effects of loss-of-function mutations, HYDIN mutant respiratory cilia lack the C2b projection of the central pair (CP) apparatus; similar findings were reported in Hydin-deficient Chlamydomonas and mice. High-speed videomicroscopy demonstrated markedly reduced beating amplitudes of respiratory cilia and stiff sperm flagella. Like the hy3 mouse model, all nine PCD-affected persons had normal body composition because nodal cilia function is apparently not dependent on the function of the CP apparatus.

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.

Preschool referral to a PCD center was not associated with better spirometry or BMI. PCD children and adolescents receiving centralized care show steady BMI and spirometry during medium term follow-up. There was a high prevalence of Pseudomonas aeruginosa infection, but the evolution of spirometry or BMI was not affected by this microorganism in medium term. Despite our longitudinal analysis showed no differences between the three centers, the assessment of spirometry and BMI over time represents a quality improvement tool. Future studies are needed to highlight the role of spirometry and BMI in long term PCD management and identify subgroups of patients with a higher risk of early lung failure or nutritional problems.

BackgroundThe lung clearance index (LCI) derived from the multiple breath inert gas washout (MBW) test reflects global ventilation distribution inhomogeneity. It is more sensitive than forced expiratory volume in 1 s (FEV 1 ) for detecting abnormal airway function and correlates closely with structural lung damage in children with cystic fibrosis, which shares features with primary ciliary dyskinesia (PCD). Normalised phase III slope indices S cond and S acin reflect function of the small conducting and acinar airways, respectively. The involvement of the peripheral airways assessed by MBW tests has not been previously described in PCD. Methods A cross-sectional MBW study was performed in 27 children and adolescents with verified PCD, all clinically stable and able to perform lung function tests. LCI, S cond (n¼23) and S acin (n¼23) were derived from MBW using a mass spectrometer and sulfur hexafluoride as inert marker gas. MBW indices were compared with present age, age at diagnosis and spirometry findings, and were related to published normative values. Results LCI, S cond and S acin were abnormal in 85%, 96% and 78% of patients with PCD and in 81%, 93% and 79%, respectively, of 13/27 subjects with normal FEV 1 . LCI and S acin correlated significantly while S cond did not correlate with any other lung function parameters. None of the lung function measurements correlated with age or age at diagnosis. Conclusions PCD is characterised by marked peripheral airway dysfunction. MBW seems promising in the early detection of lung damage, even in young patients with PCD. The relationship of MBW indices to the outcome of long-term disease and their role in the management of PCD need to be assessed.

BackgroundNasal nitric oxide (nNO) measurement is an established first line test in the work-up for primary ciliary dyskinesia (PCD). Tidal breathing nNO (TB-nNO) measurements require minimal cooperation and are potentially useful even in young children. Hand-held NO devices are becoming increasingly widespread for asthma management. Therefore, we chose to assess whether hand-held TB-nNO measurements reliably discriminate between PCD, and Healthy Subjects (HS) and included Cystic Fibrosis (CF) patients as a disease control group known to have intermediate nNO levels.MethodsIn this cross sectional, single centre, single occasion, proof-of-concept study in children and adults with PCD and CF, and in HS we compared feasibility, success rates, discriminatory capacity, repeatability and agreement between a hand-held electrochemical device equipped with a nNO software application sampling at flow rates 2 ml/s or 5 ml/s, and two stationary chemiluminescence devices, applying both tidal breathing and velum closure techniques.ResultsMeasurements were done in 16 PCD patients, 21 patients with CF and 20 HS aged between 3.8 and 60.9 years. Hand-held TB-nNO showed high success rate (96.5–100%) vs. velum closure nNO techniques (70.2–89.5%). Hand-held TB-nNO sampling at flow rate 5 ml/s showed equally high discriminative power (PCD vs. HS [p<0.0001] and PCD vs. CF [p<0.0001]) and reaching close to 100% sensitivity and specificity, superior repeatability (CV% = 10%) and equal limits of agreement compared to TB-nNO by stationary devices and even compared to velum closure sampling.ConclusionHand-held TB-nNO discriminates significantly between PCD, CF and HS and shows promising potential as a widespread targeted case-finding tool for PCD, although further studies are warranted before implementation.

Our study strongly suggests that PCD is a disease of serious threat to lung function already at preschool age, and with a high degree of variation in courses of lung function after diagnosis that was not linked to either age or level of lung function at diagnosis. Early diagnosis did not protect against decline in lung function.

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Nasal nitric oxide (NO) discriminates between patients with primary ciliary dyskinesia (PCD) and healthy individuals. We report feasibility of measurement and natural evolution of nasal NO and upon the impact of respiratory tract infection (RTI) on nasal NO in healthy infants (HI), followed from birth until age 2 years, with comparison to nasal NO in infant PCD.Tidal-breathing nasal NO measurements were performed at scheduled visits at 2 weeks old and at 4, 8, 12, 18 and 24 months old, with extra visits during RTIs. Historical nasal NO measurements for infant PCD were included for comparison.Altogether, 224 nasal NO measurements were performed in 44 enrolled infants. Median newborn nasal NO was 46 ppb (interquartile range (IQR) 29-69 ppb), increasing at a rate of 5.4% per month up to 283 ppb (IQR 203-389 ppb) at the age of 2 years. RTIs in 27 out of 44 infants temporarily suppressed nasal NO by 79%. Values for nasal NO in seven infants with PCD ranged from 6-80 ppb. The success rate to accept nasal NO sampling was 223 out of 224 measurements (99.6%).Tidal-breathing nasal NO measurement was indeed feasible in infancy and nasal NO in HI increased significantly up to 2 years of age, in opposition to nasal NO in PCD cases, which stayed low past 2 years of age. RTI episodes caused marked, temporary reductions in nasal NO in HI indistinguishable from that in infant PCD, suggesting that nasal NO should be measured in RTI-free intervals.