Primary ciliary dyskinesia in Volendam: Diagnostic and phenotypic features in patients with a CCDC114 mutation

Primary ciliary dyskinesia (PCD) is a heterogeneous disease, with impaired mucociliary clearance causing respiratory tract infections. A founding CCDC114 mutation has led to a relatively homogeneous and large Dutch PCD population in Volendam. Our aim was to describe their phenotype. Therefore, all Volendam PCD patients seen at the Amsterdam UMC were included in this study. Data were collected on lung function, microbiology, radiology, and ear‐nose‐throat (ENT) symptoms. A mixed effects model estimated lung function decline in %point per year (95% confidence interval [CI]). Thirty‐three (60%) out of approximately 56 Volendam PCD patients were treated at our center and included in this study. Only 30% of patients had situs inversus. FEV₁ declined in children (−1.43%/year, CI: −1.80/−1.05), but not in adults (0.01%/year, CI: −0.36/0.38). Pseudomonas aeruginosa was cultured in 21% of children and 60% of adults, respectively. Patients who have been infected at some point with P. aeruginosa had a steeper decline in FEV₁ as compared to patients that have never been infected. Neonatal symptoms (79%) and ENT problems (94%) were common; fertility issues however, were not (11%) common. Compared to other PCD cohorts, the Volendam/CCDC114 patients have a moderately severe phenotype with lung function decline predominantly occurring in childhood.

Targeted exhaled breath analysis for detection of Pseudomonas aeruginosa in cystic fibrosis patients

BACKGROUND

Pseudomonas aeruginosa (PA) is an important respiratory pathogen for cystic fibrosis (CF) patients. Routine microbiology surveillance is time-consuming, and is best performed on expectorated sputum. As alternative, volatile organic compounds (VOCs) may be indicative of PA colonisation. In this study, we aimed to identify VOCs associated with PA in literature and perform targeted exhaled breath analysis to recognize PA positive CF patients non-invasively.

METHODS

This study consisted of 1) a literature review to select VOCs of interest, and 2) a cross-sectional CF study. Definitions used: A) PA positive, PA culture at visit/chronically; B) PA free, no PA culture in ≥12 months. Exhaled VOCs were identified via quadrupole MS. The primary endpoint was the area under the receiver operating characteristics curve (AUROCC) of individual VOCs as well as combined VOCs against PA culture.

RESULTS

241 VOCs were identified in literature, of which 56 were further evaluated, and 13 could be detected in exhaled breath in our cohort. Exhaled breath of 25 pediatric and 28 adult CF patients, PA positive (n=16) and free (n=28) was available. 3/13 VOCs were significantly (p<0.05) different between PA groups in children; none were in adults. Notably, a composite model based on 5 or 1 VOC(s) showed an AUROCC of 0.86 (CI 0.71-1.0) and 0.87 (CI 0.72-1.0) for adults and children, respectively.

CONCLUSIONS

Targeted VOC analysis appears to discriminate children and adults with and without PA positive cultures with clinically acceptable sensitivity values.

Diagnostic yield of a targeted gene panel in primary ciliary dyskinesia patients

We aimed to determine the diagnostic yield of a targeted-exome panel in a cohort of 74 Dutch primary ciliary dyskinesia (PCD) patients. The panel consisted of 26 PCD-related and 284 candidate genes. To prioritize PCD candidate genes, we investigated the transcriptome of human airway cells of 12 healthy volunteers during in vitro ciliogenesis and hypothesized that PCD-related genes show significant upregulation. We compared gene expression in epithelial precursor cells grown as collagen monolayer and ciliated cells grown in suspension by RNA sequencing. All genes reported as PCD causative, except NME8, showed significant upregulation during in vitro ciliogenesis. We observed 67.6% diagnostic yield when testing the targeted-exome panel in our cohort. There was relatively high percentage of DNAI and HYDIN mutations compared to other countries. The latter may be due to our solution for the problem of the confounding HYDIN2 pseudogene. Candidate genes included two recently published PCD-related genes DNAJB13 and PIH1D3; identification of the latter was a direct result of this study. In conclusion, we demonstrate 67.6% diagnostic yield by targeted exome sequencing in a Dutch PCD population and present a highly sensitive and moderately specific approach for identification of PCD-related genes, based on significant upregulation during in vitro ciliogenesis.

A randomised controlled trial on the effect of inhaled hypertonic saline on quality of life in primary ciliary dyskinesia

Hypertonic saline inhalation lowers airway mucous viscosity. Increased cough transportability may improve quality of life (QoL) in primary ciliary dyskinesia (PCD).In this randomised controlled trial (RCT), PCD patients received twice-daily inhalations of hypertonic (7%) saline or isotonic (0.9%) saline for 12 weeks, with 4 weeks washout during crossover. Primary outcome was change in QoL measured by the St George's Respiratory Questionnaire (SGRQ) total score. Secondary outcomes were SGRQ subscores, Quality of Life Questionnaire-Bronchiectasis (QoL-B) scores, lower respiratory tract infection symptoms, exacerbations, spirometry, systemic and sputum inflammatory markers, adherence, and adverse events.There was no significant change in median (interquartile range) SGRQ total score between hypertonic saline (-2.6 (-9.0-1.5)) and isotonic saline (-0.3 (-8.1-6.1)) in 22 patients (age range 22-73 years) (p=0.38). QoL-B Health Perception scale improved with hypertonic saline (p=0.03). Adverse events occurred more frequently with hypertonic saline, but were mild.12 weeks of inhaled hypertonic saline did not improve SGRQ total score in adult PCD patients in this RCT, but the sample size was small. On the secondary and more disease-specific end-point of the QoL-B, a significant improvement was observed in the Health Perception scale. This study found little evidence to support the hypothesis that hypertonic saline improves QoL in PCD patients. We advise the use of disease-specific outcome measures in future trials.

Mutations in PIH1D3 Cause X-Linked Primary Ciliary Dyskinesia with Outer and Inner Dynein Arm Defects

Defects in motile cilia and sperm flagella cause primary ciliary dyskinesia (PCD), characterized by chronic airway disease, infertility, and left-right body axis disturbance. Here we report maternally inherited and de novo mutations in PIH1D3 in four men affected with PCD. PIH1D3 is located on the X chromosome and is involved in the preassembly of both outer (ODA) and inner (IDA) dynein arms of cilia and sperm flagella. Loss-of-function mutations in PIH1D3 lead to absent ODAs and reduced to absent IDAs, causing ciliary and flagellar immotility. Further, PIH1D3 interacts and co-precipitates with cytoplasmic ODA/IDA assembly factors DNAAF2 and DNAAF4. This result has clinical and genetic counseling implications for genetically unsolved male case subjects with a classic PCD phenotype that lack additional phenotypes such as intellectual disability or retinitis pigmentosa.

Diagnostic Methods in Primary Ciliary Dyskinesia

Diagnosing primary ciliary dyskinesia is difficult. With no reference standard, a combination of tests is needed; most tests require expensive equipment and specialist scientists. We review the advances in diagnostic testing over the past hundred years, with emphasis on recent advances. We particularly focus on use of high-speed video analysis, transmission electron microscopy, nasal nitric oxide and genetic testing. We discuss the international efforts that are in place to advance the evidence base for diagnostic tests.

Breathomics in lung disease

Volatile organic compounds (VOCs) are produced by virtually all metabolic processes of the body. As such, they have potential to serve as noninvasive metabolic biomarkers. Since exhaled VOCs are either derived from the respiratory tract itself or have passed the lungs from the circulation, they are candidate biomarkers in the diagnosis and monitoring of pulmonary diseases in particular. Good examples of the possibilities of exhaled volatiles in pulmonary medicine are provided by the potential use of VOCs to discriminate between patients with lung cancer and healthy control subjects and to noninvasively diagnose infectious diseases and the association between VOCs and markers of disease activity that has been established in obstructive lung diseases. Several steps are, however, required prior to implementation of breath-based diagnostics in daily clinical practice. First, VOCs should be studied in the intention-to-diagnose population, because biomarkers are likely to be affected by multiple (comorbid) conditions. Second, breath collection and analysis procedures need to be standardized to allow pooling of data. Finally, apart from probabilistic analysis for diagnostic purposes, detailed examination of the nature of volatile biomarkers not only will improve our understanding of the pathophysiologic origins of these markers and the nature of potential confounders but also can enable the development of sensors that exhibit maximum sensitivity and specificity toward specific applications. By adhering to such an approach, exhaled biomarkers can be validated in the diagnosis, monitoring, and treatment of patients in pulmonary medicine and contribute to the development of personalized medicine.

Exhaled breath analysis using electronic nose in cystic fibrosis and primary ciliary dyskinesia patients with chronic pulmonary infections

The current diagnostic work-up and monitoring of pulmonary infections may be perceived as invasive, is time consuming and expensive. In this explorative study, we investigated whether or not a non-invasive exhaled breath analysis using an electronic nose would discriminate between cystic fibrosis (CF) and primary ciliary dyskinesia (PCD) with or without various well characterized chronic pulmonary infections. We recruited 64 patients with CF and 21 with PCD based on known chronic infection status. 21 healthy volunteers served as controls. An electronic nose was employed to analyze exhaled breath samples. Principal component reduction and discriminant analysis were used to construct internally cross-validated receiver operator characteristic (ROC) curves. Breath profiles of CF and PCD patients differed significantly from healthy controls p = 0.001 and p = 0.005, respectively. Profiles of CF patients having a chronic P. aeruginosa infection differed significantly from to non-chronically infected CF patients p = 0.044. We confirmed the previously established discriminative power of exhaled breath analysis in separation between healthy subjects and patients with CF or PCD. Furthermore, this method significantly discriminates CF patients suffering from a chronic pulmonary P. aeruginosa (PA) infection from CF patients without a chronic pulmonary infection. Further studies are needed for verification and to investigate the role of electronic nose technology in the very early diagnostic workup of pulmonary infections before the establishment of a chronic infection.

Primary ciliary dyskinesia: From diagnosis to molecular mechanisms

Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disorder affecting motile cilia. This can lead to neonatal respiratory distress, early onset upper and lower airway infections, laterality abnormalities and sub- or infertility. Although disease progression shows large individual variability, all adult patients eventually develop extensive bronchiectasis. As in cystic fibrosis, early diagnosis and frequent follow-up with microbiological control is the best therapeutic strategy, as other treatment options are lacking. PCD is underdiagnosed and diagnosed late due to clinical unawareness, limited availability of diagnostic tests and difficult interpretation of test results. Diagnosis is currently based on a combination of assessment of ciliary motion and ultrastructure by high-speed video microscopy and electron microscopy, respectively. As nasal nitric oxide is low in almost all PCD patients, these measurements can be used for screening. Although there are 26 PCD genes known so far, the genetic basis of the disease has not been unraveled in an estimated 30-40% of patients. However, the rapid discovery of novel PCD genes in recent years is expected to enable accurate genetic characterization of most patients in the near future. Large-scale use of next-generation sequencing and the availability of large ciliary proteomic and transcriptomic databases accelerate the identification of novel PCD genes, especially those that play a key role in cytoplasmic assembly of ciliary ultrastructural components. These genetic advances are revolutionizing the process of obtaining a molecular diagnosis for PCD as we speak and may ultimately lead to an increased understanding of ciliogenesis and function, providing novel handles for therapeutic interventions in PCD patients.

Exhaled molecular profiles in the assessment of cystic fibrosis and primary ciliary dyskinesia

BACKGROUND

Early diagnosis and monitoring of disease activity are essential in cystic fibrosis (CF) and primary ciliary dyskinesia (PCD). We aimed to establish exhaled molecular profiles as the first step in assessing the potential of breath analysis.

METHODS

Exhaled breath was analyzed by electronic nose in 25 children with CF, 25 with PCD and 23 controls. Principle component reduction and canonical discriminant analysis were used to construct internally cross-validated ROC curves.

RESULTS

CF and PCD patients had significantly different breath profiles when compared to healthy controls (CF: sensitivity 84%, specificity 65%; PCD: sensitivity 88%, specificity 52%) and from each other (sensitivity 84%, specificity 60%). Patients with and without exacerbations had significantly different breath profiles (CF: sensitivity 89%, specificity 56%; PCD: sensitivity 100%, specificity 90%).

CONCLUSION

Exhaled molecular profiles significantly differ between patients with CF, PCD and controls. The eNose may have potential in disease monitoring based on the influence of exacerbations on the VOC-profile.

Splice-site mutations in the axonemal outer dynein arm docking complex gene CCDC114 cause primary ciliary dyskinesia

Defects in motile cilia and sperm flagella cause primary ciliary dyskinesia (PCD), characterized by chronic airway disease, infertility, and left-right laterality disturbances, usually as a result of loss of the outer dynein arms (ODAs) that power cilia/flagella beating. Here, we identify loss-of-function mutations in CCDC114 causing PCD with laterality malformations involving complex heart defects. CCDC114 is homologous to DCC2, an ODA microtubule-docking complex component of the biflagellate alga Chlamydomonas. We show that CCDC114 localizes along the entire length of human cilia and that its deficiency causes a complete absence of ciliary ODAs, resulting in immotile cilia. Thus, CCDC114 is an essential ciliary protein required for microtubular attachment of ODAs in the axoneme. Fertility is apparently not greatly affected by CCDC114 deficiency, and qPCR shows that this may explained by low transcript expression in testis compared to ciliated respiratory epithelium. One CCDC114 mutation, c.742G>A, dating back to at least the 1400s, presents an important diagnostic and therapeutic target in the isolated Dutch Volendam population.