Distinct Phenotypes of Primary Ciliary Dyskinesia in Monozygotic Twins with Defective HYDIN Gene: a Case Report

Nasal Nitric Oxide: Clue to a Diagnosis of 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.

Sir, Primary ciliary dyskinesia (PCD) is a rare autosomal recessive condition affecting the structure and function of motile cilia, thereby resulting in impairment of mucociliary clearance.[1] The common manifestations in children include neonatal respiratory distress, early-onset chronic wet cough, and recurrent respiratory infections, leading to bronchiectasis, recurrent rhinosinusitis, and middle ear infections.[1] Around one-half of PCD patients have dextrocardia and/or situs inversus totalis.[2] In the reproductive age group, PCD can be associated with male infertility and subfertility in females.[1] Diagnosis of PCD involves identification of the clinical phenotype and a combination of tests that require expertise to conduct and interpret the results.[3] The upfront screening tests are nasal nitric oxide measurement and high-speed video microscopy of nasal brushings for ciliary beat pattern and frequency [Figure 1].[3] Hallmark ciliary ultrastructure abnormalities and/or bi-allelic disease-causing mutations in known PCD genes would be diagnostic.[3] PCD can occur in the presence of normal ciliary ultrastructure, and at present, genetic testing can identify mutations in more than 80% of PCD patients.[4] Due to lack of awareness among clinicians and nonavailability of diagnostic tests, PCD is underdiagnosed and the exact frequency of PCD in India is still not known. We report a 14-year-old boy with PCD due to DRC1/CCDC164 mutation for the first time from the Indian subcontinent.Figure 1: High-speed video microscopyA 14-years-old boy, born to nonconsanguineous parents, presented to us with purulent nasal discharge, persistent productive cough, and recurrent respiratory infections with wheeze since infancy. He was born at term and did not have respiratory distress in the neonatal period. His weight and height were on the third centile. He had purulent nasal discharge and auscultation of his chest revealed bilateral crackles and wheeze. High-resolution chest tomography revealed right upper lobe collapse and centrilobular opacities. Sweat chloride estimation and serum immunoglobulin profile were within normal limits. Primary ciliary dyskinesia rule,[5] a predictive score with seven simple questions to predict the likelihood of having PCD, was 4, i.e., the likelihood of PCD was not high. Nasal nitric oxide analysis using portable electrochemical device, NIOX VERO®(Circassia, Sweden), was very low at 11.6 ppb (3.5 nl/min). High-speed video microscopy analysis (HSVA) of nasal brushings revealed motile cilia with stiff motility (reducing bending capacity) and a ciliary beat frequency of 14 Hz. The HSVA videos were reviewed by PCD team, Southampton University Hospital, UK. EDTA peripheral blood sample was sent for targeted next-generation targeted sequencing of the genes known to be associated with PCD. A homozygous nonsense variation in exon 10 of the DRC1 gene (chr2:26667625G>A; depth: 70x) that results in a stop codon and premature truncation of the protein at codon 402 (p. Trp402Ter; ENST00000288710.2) was detected. He is being managed by a multidisciplinary team and is under follow-up. PCD can be caused by bi-allelic mutations in the DRC1/CCDC164 gene.[6] This disorder characteristically starts in infancy with chronic sinopulmonary infections due to abnormal ciliary function.[6] The available literature shows that individuals with DRC1/CCDC164 mutations do not have any abnormal left–right body symmetry.[6] Our patient did not have any left–right body asymmetry. HSVA from our patient showed uniformly stiff cilia. These findings are similar to previous reports in PCD with documented DRC1/CCDC164 mutation.[6] We did not perform transmission electron microscopy due to lack of this facility at our center. PCD with normal body symmetry makes diagnosis even more difficult and late. When there is a strong suspicion based on other clinical features, we should proceed with diagnostic testing for PCD. Early diagnosis of PCD and prompt intervention have the potential to stall the progression of disease. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Dr. Antony Terance Benjamin received NIOX VERO® equipment as a research grant from Circassia, Sweden. Conflicts of interest There are no conflicts of interest. Acknowledgments We would like to acknowledge Dr. Louis Balan, Molecular Pathologist, Coimbatore, India, Dr. Janice Coles, PCD Diagnostic Service, University Hospital Southampton, UK, and Medgenome Labs, Bangalore, India.

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.

Primary Ciliary Dyskinesia (PCD) is a rare inherited multi-genic disorder of mucociliary function. Patients with indicative clinical profiles referred to the UK specialist PCD service receive a diagnosis based on multiple factors. These include high-speed video microscopy (HSVM) analysis of ciliary beat pattern (CBP) and ciliary beat frequency (CBF) at 37°C (for in vivo modelling). In PCD, ciliary axonemal defects generate abnormal CBP with/without abnormal CBF. Corresponding and predominant ultrastructural defects are determined by TEM, except in atypical cases. We report an atypical PCD patient (8 months old) with respiratory and nasal symptoms since birth, situs inversus and serous otitis media. HSVM confirmed abnormal and hyperfrequent ciliary function at 37°C on four occasions, but normal ciliary ultrastructure. On two occasions CBP and CBF (mean ±SD) were assessed at 37oC and room temperature (21-24°C). At 37°C CBF was hyperfrequent (34.4 Hz ±13.5 n=11; 26.3 Hz ±3.4 n=6) and CBP consistently abnormal with interrupted, short range, dyskinetic motility. However at room temperature the same cilia reverted to CBF (15.2 Hz ±4.5 n=2; 12.6 Hz ±0.8 n=6) within our normal range (11-20 Hz) with improved ciliary coordination and range of movement, suggesting a PCD variant with temperature sensitive CBP. Recent research suggests that healthy human epithelium maintains a normal CBP at temperatures as low as 2°C, and low temperature ciliary analysis may diagnostically replace HSVM. However, in light of our case study we conclude that temperature sensitive variants of PCD may exist and CBP analysis below 37°C without HSVM may risk PCD misdiagnosis.

<b>Introduction:</b> Primary Ciliary Dyskinesia (PCD) is a genetic, motile respiratory ciliopathy lacking normal ciliary assembly, ultrastructure and function causing impaired muco-ciliary clearance and progressive loss of lung function. <b>Aims and objectives:</b> We investigated lifelong changes in lung function in relation to genetics and ultrastructural defects hypothesizing that patients with mutations in genes affecting similar components would have a diverse progression of FEV₁ %-predicted. <b>Methods:</b> We retrieved spirometry data from the past 40 years in genetically characterized patients with PCD (NGS analysis of 34 genes). Associated ultrastructural defects formed 5 groups of patients in which slopes of FEV₁ %-predicted were estimated using a linear mixed effects model (fig). <b>Results:</b> We included 99 patients, mean (SD) age of 13.8 (±11.4) years at first spirometry (range 4-76.9) with follow up ranging (median) from 0 to 40.9 (13.2) years and a total of 5013 lung function tests. The IDA/CA/MTD (fig) group had the lowest intercept (75.8% vs. other groups ranging from 88.4-94.2%) but a faster rate of decline was seen in the ODA/IDA and other group. <b>Conclusions:</b> People with IDA/CA/MTD defects had a lower lung function already in childhood but a slower deterioration compared to people with ODA/IDA or non-specific defects who converge towards similar lung functions in later life.

BackgroundThe mutations in the RPGR (retinitis pigmentosa GTPase regulator) gene are the most common cause of X-linked retinitis pigmentosa (XLRP), a rare genetic disorder affecting the photoreceptor cells in the retina. Several reported cases identified this gene as a genetic link between retinitis pigmentosa (RP) and primary ciliary dyskinesia (PCD), characterised by impaired ciliary function predominantly in the respiratory tract. Since different mutations in the same gene can result in various clinical manifestations, it is important to describe a correlation between the gene variant and the observed phenotype.MethodsTwo young brothers from a non-consanguineous Slovak family with diagnosed retinal dystrophy and recurrent respiratory infections were examined. Suspected PCD was diagnosed based on a PICADAR questionnaire, nasal nitric oxide analysis, transmission electron microscopy, high-speed video microscopy analysis, and genetic testing.ResultsWe identified a novel frameshift RPGR mutation NM_001034853: c.309_310insA, p.Glu104Argfs*12, resulting in a complex X-linked phenotype combining PCD and RP. In our patients, this mutation was associated with normal ultrastructure of respiratory cilia, reduced ciliary epithelium, more aciliary respiratory epithelium, shorter cilia, and uncoordinated beating with a frequency at a lower limit of normal beating, explaining the clinical manifestation of PCD in our patients.ConclusionThe identified novel pathogenic mutation in the RPGR gene expands the spectrum of genetic variants associated with the X-linked PCD phenotype overlapping with RP, highlighting the diversity of mutations contributing to the disorder. The described genotype–phenotype correlation can be useful in clinical practice to recognise a broader spectrum of PCD phenotypes as well as for future research focused on the genetic basis of PCD, gene interactions, the pathways implicated in PCD pathogenesis, and the role of RPGR protein for the proper functioning of cilia in various tissues throughout the body.

Primary ciliary dyskinesia (PCD) is a rare genetic disorder of ciliary structure and function. The diagnosis can be challenging, particularly when using nongenetic assays. The "gold standard" diagnostic test is ultrastructural analysis of respiratory cilia obtained by nasal scrape or brush biopsy. A few specialized centers use high-speed videomicroscopy to examine ciliary beat. Certain beat patterns correlate with ultrastructural defects, and, in some cases, subtle alterations in beat pattern can be seen when ultrastructure is normal. Recent studies have shown that nasal nitric oxide (NO) is very low in patients with PCD compared with healthy control subjects; therefore, this assay may be a useful screening or adjunctive test for PCD. Because acute respiratory illnesses may yield alterations in ciliary ultrastructure, ciliary beat, and nasal NO values, these tests should be performed during a stable baseline period. Identification of an array of PCD genes has provided the opportunity for making a definitive genetic diagnosis for PCD in some cases. All of these approaches have a role in diagnosing PCD. For example, PCD has been confirmed by identifying disease-causing mutations in a heavy dynein chain gene in individuals with normal ciliary ultrastructure but subtle defects in ciliary beat and low nasal NO. Priorities to improve nongenetic diagnostic capability include standardization of nasal NO as a screening test and the development of specialized centers using uniform approaches for the analysis of ciliary ultrastructure and ciliary beat pattern. Another chapter in this issue (see Zariwala and colleagues, pp. 430) addresses the progress toward improved capabilities for definitive genetic testing.

Background Primary ciliary dyskinesia (PCD) is a clinical syndrome characterized by cilia with an abnormal structure or function. Its main clinical manifestations comprise chronic bronchitis, cough, recurrent respiratory infections, situs inversus, and male infertility. Single-gene variants are widely assumed to be the main cause of this rare disease, and more than 40 genes have been described to be associated with its onset. CCDC39 is essential for assembling the inner dynein arms and dynein regulatory complex and is important in cilia motility. CCDC39 variants were reported as a monogenic etiology of PCD. Methods This study investigated two unrelated Chinese patients diagnosed as PCD. The chest computed tomography scan was performed to identify PCD phenotypes of the two probands. Considering the effect of PCD on male fertility, routine semen analysis, sperm morphology examination, and scanning electron microscopy were performed to assess the semen characteristics of male proband in family 2 (F2 II-1), who had a history of infertility. Subsequently, the peripheral blood samples of probands were collected to perform whole-exome sequencing (WES) to explore the possible genetic causes of this disease. Results Whole-exome sequencing revealed a homozygous CCDC39 variant in the female proband of family 1 (F1 II-1: c.286C>T:p.Arg96Ter) and two compound heterozygous CCDC39 variants in the male proband of family 2 (F2 II-1: c.732_733del: p.Ala245PhefsTer18; c.2800_2802dup:p.Val934dup). The two probands showed the typical PCD phenotypes, including chronic bronchitis, recurrent respiratory infections, and situs inversus. The male proband also showed oligoasthenoteratospermia with multiple morphological abnormalities of the sperm flagella. Additionally, CCDC39 protein level was significantly lower in the sperm of male proband than in the sperm from normal controls. Conclusion We identified a homozygous variant reported previously and two compound heterozygous variants of CCDC39 possibly responsible for PCD pathogenesis, expanding the variant spectrum of Chinese PCD, Kartagener syndrome, and morphological abnormalities of the sperm flagella involving CCDC39.

Introduction Primary ciliary dyskinesia (PCD) is a rare genetic disorder causing defective ciliary function and impaired mucociliary clearance. Features include chronic bronchiectasis, recurrent infections, and, in 50% of cases, situs inversus which indicates Kartagener's syndrome (KS). Due to the rarity of PCD and its subtle onset, diagnosis is frequently delayed. This case highlights the importance of early recognition of clinical features linked to PCD and demonstrates targeted management strategies. Case Presentation This is a 77-year-old male with a history of complete situs inversus with dextrocardia, recurrent sinopulmonary infections (8-10 episodes in his lifetime), hypertension, reported asthma, rhinitis, and a remote smoking history. He presented with exertional dyspnea. PFT revealed a mild obstructive ventilatory defect with evidence of air trapping. Despite proper inhaler technique, he reported worsening exertional dyspnea with productive cough, greenish sputum production and nasal congestion. CT chest revealed dextrocardia with significant bronchial wall thickening and bilateral bronchiectasis. Situs inversus with a right-sided aortic arch was also noted. Due to these findings, KS was suspected. Workup for bronchiectasis was performed. The patient ultimately tested homozygous for a DNAAF11 gene mutation, confirming a diagnosis of PCD. His fluticasone propionate and salmeterol inhalation powder was discontinued to avoid potential adverse effects associated with PCD. Treatment included supportive care and mucus clearance techniques including chest physiotherapy and flutter valve; mucolytics were prescribed. Tiotropium bromide was prescribed due to emphysema noted on imaging, presence of wheezing, and increased albuterol use. Discussion This case illustrates the diagnostic (genetic testing and imaging) and management considerations for PCD complicated by KS. Situs inversus and bronchiectasis suggested KS, later confirmed through genetic testing (previously via biopsy) for DNAAF11. This mutation disrupts ciliary function, leading to impaired clearance and recurrent infections. Management for PCD prioritizes airway clearance and prevention of bronchiectasis progression. Supportive measures were utilized, and medications with potential adverse effects on mucociliary function were avoided, in this case fluticasone/salmeterol due to its ability to remain bound to motile respiratory cilia. When available, hypertonic saline is preferred. Imaging findings and recurrent symptoms underscored the need for aggressive management to reduce exacerbations. This case highlights the utility of genetic testing in confirming this rare condition, especially for patients with respiratory symptoms. Early diagnosis allows for tailored care, slowing disease progression and improving quality of life. Clinicians should consider PCD in patients with recurrent respiratory infections and structural abnormalities, particularly with situs inversus.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous recessive disorder of motile cilia that leads to oto-sino-pulmonary diseases and organ laterality defects in approximately 50% of cases. The estimated incidence of PCD is approximately 1 per 15,000 births, but the prevalence of PCD is difficult to determine, primarily because of limitations in diagnostic methods that focus on testing ciliary ultrastructure and function. Diagnostic capabilities have recently benefitted from (1) documentation of low nasal nitric oxide production in PCD and (2) discovery of biallelic mutations in multiple PCD-causing genes. The use of these complementary diagnostic approaches shows that at least 30% of patients with PCD have normal ciliary ultrastructure. More accurate identification of patients with PCD has also allowed definition of a strong clinical phenotype, which includes neonatal respiratory distress in >80% of cases, daily nasal congestion and wet cough starting soon after birth, and early development of recurrent/chronic middle-ear and sinus disease. Recent studies, using advanced imaging and pulmonary physiologic assessments, clearly demonstrate early onset of lung disease in PCD, with abnormal air flow mechanics by age 6-8 years that is similar to cystic fibrosis, and age-dependent onset of bronchiectasis. The treatment of PCD is not standardized, and there are no validated PCD-specific therapies. Most patients with PCD receive suboptimal management, which should include airway clearance, regular surveillance of pulmonary function and respiratory microbiology, and use of antibiotics targeted to pathogens. The PCD Foundation is developing a network of clinical centers, which should improve diagnosis and management of PCD.

<b>Background:</b> Primary Ciliary Dyskinesia (PCD) is a genetic and predominantly motile respiratory ciliopathy lacking normal ciliary assembly, ultrastructure and function causing impaired muco-ciliary clearance. Clinical manifestations include oto-sino-pulmonary symptoms, subfertility and situs inversus. However, another important role of motile cilia is found in the development of otolith organs in zebrafish, although this has yet to be evaluated in humans with PCD. <b>Aims:</b> we examined the vestibular function in patients with PCD using a relevant armamentarium of validated and standardized clinical tests to explore any abnormalities in function. <b>Methods:</b> this was a single centre cross sectional, exploratory study in patients with PCD. Vestibular, inner and middle ear assessments, including cervical vestibular evoked myogenic potentials (cVEMP), video head impulse test (vHIT), audiometry, tympanometry, and complemented with the validated Dizziness Handicap Inventory (DHI) questionnaire were performed. <b>Results:</b> 10 patients aged 22–67 yrs, median 29, were recruited. Six patients had affected saccule-function with uni- or bilateral absent potential in the cVEMP test. No patients had pathological vHIT. One patient had mild vertigo according to the DHI questionnaire. Four patients had a minor uni- or bilateral conductive hearing loss as the result of otitis media with effusion. <b>Conclusion:</b> more than half of patient in this small exploratory study had affected saccule function. All had normal function of the semicircular canals, suggesting that a possible affection of the vestibular apparatus should be sought in the otolith organs. Our findings need confirmation and to be further explored in a larger population of patients.

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 (PCD) is an autosomal recessive, rare, genetically heterogeneous condition characterized by oto-sino-pulmonary disease together with situs abnormalities (Kartagener syndrome) owing to abnormal ciliary structure and function. Most patients are currently diagnosed with PCD based on the presence of defective ciliary ultrastructure. However, diagnosis often remains challenging due to variability in the clinical phenotype and ciliary ultrastructural changes. Some patients with PCD have normal ciliary ultrastructure, which further confounds the diagnosis. A genetic test for PCD exists but is of limited value because it investigates only a limited number of mutations in only two genes. The genetics of PCD is complicated owing to the complexity of axonemal structure that is highly conserved through evolution, which is comprised of multiple proteins. Identifying a PCD-causing gene is challenging due to locus and allelic heterogeneity. Despite genetic heterogeneity, multiple tools have been used, and there are 11 known PCD-causing genes. All of these genes combined explain approximately 50% of PCD cases; hence, more genes need to be identified. This review briefly describes the current knowledge regarding the genetics of PCD and focuses on the methodologies used to identify novel PCD-causing genes, including a candidate gene approach using model organisms, next-generation massively parallel sequencing techniques, and the use of genetically isolated populations. In conclusion, we demonstrate the multipronged approach that is necessary to circumvent challenges due to genetic heterogeneity to uncover genetic causes of PCD.

Background and Objective: Primary ciliary dyskinesia (PCD) is a rare genetic disorder that affects the mucociliary system, leading to progressive lung damage. This deterioration can result in bronchiectasis, atelectasis, and respiratory failure, necessitating lung transplantation in severe cases. This study aims to assess ciliary motility and ultrastructure in the bronchial epithelium of transplanted lungs in patients with PCD to determine whether mucociliary function is preserved post-transplantation. The findings seek to enhance scientific understanding and provide prognostic insights for these patients. Materials and Methods: A prospective observational study was conducted on two patients with PCD and advanced lung disease who underwent bilateral lung transplantation. Nasal and bronchial cilia samples were analyzed using high-speed videomicroscopy and transmission electron microscopy. Follow-up assessments included ciliary function analysis, lung rejection monitoring, and quality-of-life evaluations, with follow-up extending up to 30 months post-transplant. Results: Post-transplant evaluations demonstrated normal ciliary motility and ultrastructure in the transplanted lungs throughout the study period (up to 30 months), indicating the long-term preservation of mucociliary function. Conclusions: Transplanted lungs in patients with PCD maintain normal bronchial ciliary motility and structure in the long term, suggesting a favorable prognosis for both the graft and the recipient. These findings support the feasibility and long-term effectiveness of lung transplantation in patients with PCD.