Primary ciliary dyskinesia. Recent advances in diagnostics, genetics, and characterization of clinical disease.

Primary Ciliary Dyskinesia and Cystic Fibrosis: Different Diseases Require Different Treatment

Primary ciliary dyskinesia (PCD) is a rare hereditary disorder characterized by defective motile cilia and impaired mucociliary clearance in the respiratory tract. In recent years, significant advances have been made in both clinical and basic research on PCD, especially regarding the identification of newly discovered pathogenic genes. However, early diagnosis and treatment of PCD in China still face considerable challenges. In response, a new expert consensus on the diagnosis and treatment of PCD in China has been developed. This consensus was initiated by the Genetic and Rare Lung Disease Group (Preparatory) of the Chinese Thoracic Society of the Chinese Medical Association and the China Bronchiectasis Clinical Diagnosis and Research Alliance. This consensus is based on extensive opinion collection, literature review, online and offline discussions, and previous expert consensus on PCD in China. The consensus addresses 9 core issues related to PCD, including its clinical presentation, diagnosis, treatment, patient management, and follow-up. Nine recommendations have been formulated to improve the diagnostic and therapeutic approaches to PCD in China.Issue 1: Which high-risk populations should undergo PCD screening?Recommendation 1: It is recommended to screen for PCD in patients with a history of bronchiectasis plus any one of the following: situs inversus; chronic sinusitis or nasal polyps; recurrent or chronic otitis media; infertility/subfertility; consanguinity, or a sibling or first-degree relative with a confirmed PCD diagnosis (1C).Issue 2: What is the value of imaging examinations in the diagnosis and management of PCD?Recommendation 2: For the high-risk PCD populations mentioned above, we recommend performing active imaging investigations-including chest high-resolution computed tomography (HRCT), sinus CT, and cardiac ultrasonography-to aid in the early detection of clinical features indicative of PCD, such as bronchiectasis, sinusitis, and situs inversus. In addition, for patients diagnosed with PCD, we recommend regular follow-up chest HRCT to monitor the progression of pulmonary lesions (1C).Issue 3: What is the value of transmission electron microscopy (TEM) in diagnosing PCD?Recommendation 3: For patients with a high clinical suspicion of PCD, we recommend transmission electron microscopy (TEM) for the assessment of ciliary ultrastructure. TEM serves as a direct diagnostic tool for suspected PCD. A definitive diagnosis of PCD can be made if a class 1 defect is identified (1B). If a class 2 defect is observed, the results should be interpreted in conjunction with other diagnostic findings.Issue 4: What is the value of genetic testing in PCD diagnosis, and which genetic testing strategy should be used?Recommendation 4: For patients with a high clinical suspicion of PCD, we recommend performing genetic testing using whole-exome sequencing (WES) at an early stage. WES serves as a direct diagnostic tool for suspected PCD. A definitive diagnosis can be made when biallelic pathogenic or likely pathogenic variants in known PCD-related genes are identified. During WES data analysis, it is essential to include the assessment of copy number variations (CNVs) (1C).Issue 5: What is the value of nasal nitric oxide (nNO) measurement in diagnosing PCD?Recommendation 5: nNO measurement is recommended as an adjunctive diagnostic test for suspected PCD. Using a threshold of 77 nl/min, patients with nNO values below this threshold should undergo further confirmatory PCD testing (2B).Issue 6: What is the value of high-speed video microscopy analysis (HSVA) in diagnosing PCD?Recommendation 6: In clinical settings with access to HSVA, HSVA is recommended as an adjunctive diagnostic test for suspected PCD. A positive HSVA result warrants further confirmatory testing (2C).Issue 7: What is the value of immunofluorescence (IF) in diagnosing PCD?Recommendation 7: In clinical settings where IF is available, it can be recommended as an adjunctive diagnostic test for suspected PCD. A positive IF result warrants further confirmatory testing (2D).Issue 8: How should PCD patients be followed up?Recommendation 8: Regular annual follow-up is recommended for adult PCD patients. Key follow-up components include assessment of pulmonary, sinus, and otologic symptoms and function. Additional assessments should include evaluation of disease severity, immune status, quality of life, and psychological status. Furthermore, infertility/subfertility assessment and follow-up are recommended for PCD patients of reproductive age (1C).Issue 9: How can genetic counseling assist PCD patient families in reproductive planning and decision-making?Recommendation 9: Providing appropriate genetic counselling to families of PCD patients can help identify carriers and assess the risk of offspring having PCD for individuals of reproductive age, thereby assisting them in making informed reproductive decisions (1D).

Primary Ciliary Dyskinesia

Robust diagnosis of primary ciliary dyskinesia (PCD) is important if patients are to receive appropriate specialist management before irreversible deterioration of lung function occurs. Early diagnosis also enables patients and their families to receive appropriate genetic counseling, disease-specific management of ear and rhino-sinus disease, and screening for PCD-associated problems (e.g., cardiac problems) (1, 2). The association of extremely low levels of nasal nitric oxide (nNO) in PCD has been recognized for over 15 years, and measurement of nNO is increasingly used as a screening test for PCD in Europe (1). The manuscript by Leigh and coworkers in this edition of AnnalsATS (3) provides an important advance in the use of nNO for clinical and research purposes. Their data confirm that nNO is a reliable investigation for PCD in the North American population and setting, including identification of “atypical” patients with PCD who might otherwise be missed due to normal ciliary ultrastructure. The authors provide evidence that a standardized protocol using different NO analyzers can be used to reliably differentiate patients with PCD from patients without PCD and from healthy children, in geographically dispersed centers. They have additionally developed cutoff values using data from their large study population, which can now be validated in other populations. There is no “gold standard” diagnostic test to identify all PCD phenotypes, and diagnostic workup requires access to a number of specialist investigations. Previously, ciliary ultrastructure analyzed by electron microscopy (EM) was considered diagnostic, but there is an increasing literature on normal ciliary ultrastructure, at EM resolution, in PCD. This indicates that PCD will be missed in centers where diagnosis depends solely on EM (2, 4). It is also recognized that certain EM defects previously considered diagnostic might on occasion represent secondary changes that resolve on repeat testing (4, 5). In Europe, assessment of ciliary beat frequency (CBF) and pattern (CBP) by high-resolution, high-speed video microscopy (HSVm) is recommended as a functional test for PCD (1, 6). If HSVm analysis is abnormal, re-differentiation of basal epithelial cells at an air–liquid interface (ALI) in cell culture enables reassessment of ciliary function and ultrastructure to differentiate primary from secondary dyskinesia (1). Alternatively, immunoflorescent (IF) staining of ciliary proteins can support diagnosis of PCD (7). EM, HSVm, ALI-culture, and IF all require a high degree of expertise in addition to expensive equipment and infrastructure. These techniques are therefore restricted to a few highly specialized centers, limiting easy access to diagnostic testing (8). Diagnosis supported by bi-allelic mutations in genes known to be associated with PCD is promising; currently genotyping detects only 50–65% of patients (2), but as new genes are rapidly identified this will become increasingly sensitive. The evidence provided by Leigh and coleagues (3) is therefore to be welcomed by clinicians, researchers, and in particular families who are unable to travel to a highly specialized center. It is to be hoped that the U.S. Food and Drug Administration and other regulatory authorities will approve nNO analyzers for clinical use given the evidence that nNO is a reliable screening test for PCD and that valid measurements can be taken at sites geographically distant from a diagnostic center using standardized protocols. Leigh and coworkers report a cutoff value for nNO of 77 nL/min providing sensitivity of 0.98 and specificity greater than 0.999. This cutoff value was validated across six other sites, identifying 70 of the 71 (98.6%) participants with confirmed PCD. A previous study used a cutoff for nNO of 105 parts per billion and reported a specificity of 88%, a sensitivity of 100%, and a positive predictive value of 89% for correctly diagnosing PCD (9). While there are now substantial data to demonstrate that nNO measurement is helpful in guiding the diagnostic pathway, we need to recognize limitations of this measurement. Standardized methods (10) to measure nNO are not appropriate for younger children, precisely the age group that need targeting for diagnostic measurement. Tidal measurements allow levels to be measured in young infants, although there is limited experience in this younger age group (1, 11, 12). Patients with other with upper and lower airway diseases have been reported to have reduced nNO levels, although usually not as low as in PCD; such diseases include cystic fibrosis, nasal polyps and chronic sinusitis. A few groups have recently reported normal levels of nasal NO in a minority of patients with PCD (1, 11, 13). These studies highlight that patients with a history strongly suggestive of PCD should not be excluded from further diagnostic evaluation on the basis of nNO, and also that, while providing an excellent screening test, nNO is not diagnostic and low levels should trigger referral to a highly specialized diagnostic center. A priority for researchers is to understand the cause of the extraordinarily low nNO observed in PCD (14). From a clinical perspective, the next hurdle to overcome is the lack of regulatory approvals of nNO analyzers for PCD diagnosis, as well as the cost and therefore availability of devices. Until recently, the only commercially available analyzers for measuring nNO were nonportable desktop analyzers, which are extremely expensive. More reasonably priced portable machines (15) are now available, although they are not yet fully validated nor approved for clinical use. Manufacturers should be encouraged to develop, validate, and seek approvals for user-friendly, reasonably priced nNO analyzers. This will lead to a step change in the diagnosis of PCD by reliably identifying patients for referral to specialist diagnostic centers.

RATIONALE: Primary Ciliary Dyskinesia (PCD) is a rare autosomal recessive genetic disease of ciliary function associated with suppurative respiratory tract disease affecting the sinuses, ears and lungs, often progressing to bronchiectasis, organ laterality defects, and fertility issues. PCD is often underdiagnosed, but early identification is crucial for effective management. The American Thoracic Society PCD diagnostic guidelines recommend initial screening for nasal nitric oxide (nNO) levels below 77 nanoliters per minute (nl/min) in patients with clinical features of PCD, followed by genetic testing to confirm the diagnosis. Recent estimates indicate that up to 10% of patients with idiopathic bronchiectasis without suspicion of a ciliary defect may have underlying PCD. We aimed to assess the prevalence of PCD among adults with idiopathic bronchiectasis seeking care at the University of North Carolina Bronchiectasis/NTM Care and Research Center. METHODS: We undertook an IRB approved, ongoing cross-sectional study enrolling adult patients with idiopathic bronchiectasis affecting at least one lung lobe. Any patient with a strong clinical suspicion for PCD or with previous PCD testing was excluded. Additionally, patients with clinical features of cystic fibrosis (CF) were required to have a negative CF test since CF can reduce nNO production. Each enrolled patient underwent nNO screening and all will have commercial PCD genetic panel testing. RESULTS: We have enrolled and tested 54 patients for PCD using nNO screening and genetic testing. Among the enrolled patients, 43 (79.6%) are female, with an average age of 68 years. The average nNO was 272.1 nl/min, with a range of 92.5 – 462.3 nl/min. Genetic results are pending. CONCLUSIONS: The nNO screening results suggest that none of the enrolled patients have PCD. It is possible that nNO testing may underestimate prevalence given that certain genes can be associated with higher nNO values. The planned genetic testing will help assess this possibility, but the testing will be limited by the number of genes tested, the fact that not all PCD-causing genes are known, and results that may include variants of uncertain significance. Of course, the nNO screen results may also be accurate, suggesting patients with PCD have been appropriately recognized and excluded from this study. Regardless of outcome, this work helps assess PCD underdiagnosis in idiopathic bronchiectasis patients and understand the potential value of including PCD testing as part of the standard diagnostic workup for these patients.

Primary ciliary dyskinesia (PCD) is a heterogeneous genetic disorder characterized by structural and functional abnormalities of motile cilia, leading to chronic oto-sino-pulmonary symptoms and progressive lung damage. Markers of early lung disease in PCD may help to identify individuals who may benefit from closer monitoring or earlier, more aggressive interventions. Multiple Breath Washout (MBW) offers a noninvasive assessment of ventilation distribution inhomogeneity. Whether MBW could serve as a marker of early lung disease in PCD or could be used as an efficacy endpoint in clinical trials in PCD remains to be established. This narrative review evaluates current literature on the role of MBW in early detection and tracking of PCD-related lung disease progression, focusing on its sensitivity compared to spirometry and to the results obtained in different PCD genotypes and phenotypes. Current evidence suggests that LCI outperforms spirometry in detecting early lung abnormalities, but it may also be overly sensitive in this population. The role of LCI in long-term monitoring remains uncertain, requiring more longitudinal data. Alternative MBW indices, such as Scond and Sacin, might offer additional insights into the source of ventilation heterogeneity but need further validation. Correlation of MBW with imaging is inconsistent, underscoring the need for integrated approaches. MBW, particularly LCI, shows promise as a noninvasive sensitive marker of early lung disease in PCD. However, its long-term utility in tracking PCD lung disease remain unclear. Further genotype-stratified, longitudinal studies are needed to confirm its clinical value and optimize its application in PCD management.

Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by impaired function of the ciliated epithelium. Ciliary dysfunction leads to chronic respiratory tract infections, bronchiectasis, sinusitis, and sometimes organ laterality defects (Kartagener syndrome). Diagnosis requires an analysis of clinical manifestations, measurement of nasal nitric oxide (nNO) levels, assessment of ciliary function and structure using high-speed video microscopy analysis (HSVA) and transmission electron microscopy (TEM), as well as genetic testing. Diagnosing PCD is complicated by cases with normal ciliary ultrastructure, difficulties in differentiating PCD from secondary ciliary dyskinesia, and the genetic heterogeneity of the disease. The HSVA method enables rapid evaluation of key ciliary function parameters, including ciliary beat frequency and ciliary beat pattern, making it one of the cornerstone tools in diagnosing PCD. The aim of this study was to review the HSVA method and software tools designed for the automated processing of HSVA results in PCD diagnostics. Results. The review identified 13 main software tools. The findings show that these tools provide accuracy comparable to manual analysis, facilitate data processing, and reduce the influence of human error. However, manual analysis remains predominant due to the limited availability and complexity of automated solutions. To improve diagnostic quality, further development of universal and accessible software solutions is needed, along with the standardization of HSVA data analysis approaches. Conclusion. HSVA is a pivotal diagnostic method for PCD, which evaluates the function of cilia. HSVA in combination with genetic testing and TEM has been demonstrated to facilitate the identification of the disease. The automation and standardization of HSVA, including the use of video image analysis software for ciliated epithelium, enhance the quality of diagnosis.

Though PCD usually presents after birth in term neonates, diagnosing PCD during the neonatal and infancy stages is uncommon, particularly in children who do not exhibit laterality defects. We report our recent experience with the diagnosis of PCD in the neonatal and early infantile period in a highly consanguine population. This was achieved by implementing a novel genetic-based diagnostic approach based on direct testing for recognized regional genetic variants. We conducted a retrospective analysis of children diagnosed with PCD at Soroka University Medical Center during the neonatal or early infantile period between 2020 and 2023. We included children under 3 months of age who had a genetic confirmation of PCD, as evidenced by the presence of two pathogenic variants in recognized genes. Genetic testing targeted regional genetic variants in previously identified PCD genes. Eight patients were included. The median age at diagnosis was 12.5 days. Three (38%) were born prematurely < 34 weeks gestational age. All patients were presented with respiratory distress and hypoxemia after birth. The median duration of oxygen support was 23 days, and upper lobe atelectasis was present in five patients (63%). Congenital cardiac malformation was present in four patients. Organ laterality defects were present in four patients. Genetic mutations identified were in the DNAAF5, DNAL1, DNAAF3, and DNAH1 genes. Conclusion: Neonatal diagnosis of PCD is uncommon, especially in atypical presentations such as children without laterality defects or preterms. Focusing on a genetic diagnosis of the local tribal pathogenic variants promotes a potential cost-efficient test leading to earlier diagnosis. There is a need for a standardized protocol for earlier diagnosis of PCD in high-consanguinity areas. What is Known: • Primary ciliary dyskinesia (PCD) typically presents after birth in term neonates. • Diagnosing PCD during neonatal and infancy stages is challenging, particularly in children without laterality defects. What is New: • A novel genetic-based diagnostic approach was implemented on the neonatal population in a highly consanguine community, focusing on direct testing for regional genetic variants, leading to early and rapid diagnosis of PCD.

Primary ciliary dyskinesia (PCD) is a rare and genetically heterogeneous disease and clinically characterized by neonatal respiratory distress, organ laterality defects, persistent rhinosinusitis, chronic bronchitis, and eventually bronchiectasis. Currently, there is no single “gold standard” diagnostic test for PCD. PICADAR (Primary Ciliary Dyskinesia Rule) score is a guide to decide for further evaluation of diagnostic tests in PCD. European Respiratory Society (ERS) and American Thoracic Society (ATS) recommend diagnostic tests, including nasal nitric oxide (nNO), high-speed video analysis (HSVMA), transmission electron microscopy (TEM) and genetic testing. Cryo-electron tomography and immunofluorescence methods are new techniques recently performed by specialized centers and needs to be improved. Age at diagnosis for PCD changes according to awareness of disease and available diagnostic tests in different centers. Regular follow-up and multidisciplinary approach is important in the management of PCD. The main aim of the treatment is to prevent pulmonary exacerbations and slow the progression of the disease since there are no treatment approaches to correct the underlying cilia structure and its functions in PCD. Although, there are not enough randomized controlled trials for the treatment of PCD, recent treatments are usually based on to improve the mucociliary clearance. Early diagnosis with multidisciplinary management and nutritional advice could improve growth and delay disease progression leading to bronchiectasis and lung function impairment in PCD

OBJETIVO: Revisar a discinesia ciliar primária (DCP) quanto aos seus aspectos ultra-estruturais, discriminar os defeitos ciliares primários dos secundários, descrever o quadro clínico, os testes laboratoriais de triagem e de diagnóstico disponíveis, bem como seu manejo clínico. FONTE DE DADOS: Pesquisa nas bases de dados Medline, Lilacs e SciELO, no período de 1980 a 2007. SÍNTESE DOS DADOS: A DCP é uma doença autossômica recessiva que compromete a estrutura e/ou a função ciliar e, conseqüentemente, o transporte mucociliar. As manifestações clínicas envolvem o trato respiratório superior e inferior, com infecções recorrentes do ouvido médio, seios paranasais e pulmonares, que podem evoluir para bronquiectasias. Outras manifestações incluem situs inversus totalis e infertilidade masculina. O diagnóstico deve ser suspeitado pelos pediatras em várias situações: recém-nascidos de termo com desconforto respiratório sem causa aparente; neonatos portadores de dextrocardia; lactentes com tosse persistente e/ou infecções otorrinolaringológicas de repetição, excluindo-se as imunodeficiências e a fibrose cística; crianças com asma atípica e as com bronquiectasias sem causa definida. Os testes de triagem diagnóstica são os da sacarina e do óxido nítrico nasal. As avaliações do defeito ultra-estrutural e funcional exigem análise por microscopia eletrônica e da freqüência e formato da onda de batimento ciliar. CONCLUSÕES: A DCP, apesar da baixa prevalência, é pouco diagnosticada pelas dificuldades de estabelecer o diagnóstico definitivo do defeito ciliar devido à complexidade da investigação laboratorial e pela falta de reconhecimento da doença pelos médicos. A suspeita clínica e o diagnóstico precoce são fundamentais para reduzir a morbidade e prevenir o desenvolvimento de complicações.

The human heart is strikingly asymmetrical along the left-right body axis. If one begins with the position of the heart in the left chest, continues through asymmetrical venous drainage into the atria and asymmetrical orientation of the 2 anatomically and functionally distinct ventricles, and finally proceeds through the highly asymmetrical coil of semilunar valves and great vessels, the structure and function of the human heart are precisely aligned to the left-right axis. When cardiac asymmetries either fail to develop or align incorrectly relative to each other or relative to other organs, a plethora of congenital heart disease results. This group of heart diseases is called heterotaxy syndrome and represents both a difficult clinical challenge and a fascinating window into the biology underlying one of the most fundamental embryological processes, namely, the mechanism by which an organism establishes the 3 body axes. Positioning of organs along the left-right axis can be divided into 3 broad classes: situs solitus, in which all organs are positioned normally; situs inversus, in which there is mirror image reversal of all organs; and heterotaxy, in which there is any positioning of organs along the left-right axis differing from situs solitus and situs inversus (Figure). Pure situs inversus is found in 1 of 8500 in the general population and is usually not associated with intracardiac defects. In contrast, heterotaxy has a high degree of association with intracardiac defects. It has a reported incidence of 1 of 10 000 and is associated with at least 3% of cases of congenital heart disease.1 The anatomic spectrum of organ laterality. A, Situs solitus. B, Right atrial isomerism. The liver is midline, there are 2 eparterial bronchi, the position of the stomach and cardiac apex is indeterminate, and there is asplenia. C, Left atrial isomerism. The liver is midline, there …

The global prevalence and ethnic heterogeneity of primary ciliary dyskinesia gene variants: a genetic database analysis

The gold standard for the diagnosis of primary ciliary dyskinesia (PCD) is a dynein deficiency shown with transmission electron microscopy. However, there are many cases of PCD without dynein deficiency. When considering ciliary function, there are similar problems of sensitivity in diagnosis and there is also a major lack of specificity. Based on the normal ciliary function and ultrastructure and the absence of secondary abnormalities after ciliogenesis in sequential monolayer-suspension culture, the diagnostic value of ciliary function analysis after ciliogenesis was investigated in more than 70 PCD and 640 non-PCD cases. In biopsies, ciliary immotility was found in 66% of PCD cases but was also found in 8% of non-PCD cases. PCD was later confirmed in 61% of the biopsies with ciliary immotility. Normal ciliary beat frequency (CBF) was found in 20% of PCD biopsies. Coordinated ciliary activity was observed in 10% of PCD cases. After ciliogenesis in culture, ciliary immotility was present in 78% of the PCD cases but never in non-PCD cases. CBF was normal after ciliogenesis in 7% of the PCD cases and was always found in non-PCD cases. Absence of coordinated ciliary activity was found in 100% of PCD cases and 0% of non-PCD cases. In conclusion, while ciliary function analysis in a biopsy never proves, nor excludes the diagnosis of PCD, after ciliogenesis in culture CBF measurement can be diagnostic for PCD and reaches 100% specificity and sensitivity when considering coordinated ciliary activity, making it the single 100% diagnostic parameter for PCD.

Background: Signs that raise suspicion for Primary Ciliary Dyskinesia (PCD) include neonatal respiratory distress, chronic wet cough, situs inversus and development of unexplained bronchiectasis. However the prevalence of PCD among suspect patients is unknown. We systematically reviewed the literature and estimated the prevalence of PCD in cohorts of suspect patients referred for diagnostic testing. Methods: All major electronic databases were searched from inception until December 2015 using appropriate terms. Included studies described cohorts of consecutive referrals for PCD testing in which PCD diagnosis was confirmed through a combination of at least two tests. A meta-analysis of proportions using a random effects model was performed and the pooled prevalence of PCD across studies is reported. Results: A total of eight studies were synthesized (referrals: n=2693, PCD: n=727). The pooled prevalence of newly diagnosed PCD patients in cohorts of referrals was 32% (95%CI:25%-39%, I 2 =92.0%) (Fig 1a). Subgroup analysis which excluded studies from the UK led to higher prevalence and also explained most of the heterogeneity in the effect estimate (prevalence:40%, 95%CI:36%-44%, I 2 =19.13%) (Fig 1b). Conclusion: Approximately, only one third of referred patients for PCD testing have eventually PCD confirmed. A revised referral strategy and application of screening tests could improve this figure.

Pulmonary Radioaerosol Mucociliary Clearance in Diagnosis of Primary Ciliary Dyskinesia