Primary ciliary dyskinesia: recent advances in pathogenesis, diagnosis and treatment

Case Report: A Novel Homozygous Mutation of Cyclin O Gene Mutation in Primary Ciliary Dyskinesia with Short Stature

Background

Primary ciliary dyskinesia (PCD) is a group of autosomal recessive genetic diseases caused by abnormal ciliary ultrastructure and/or function, resulting in reduced ciliary clearance function or other dysfunctions. PCD is one of the causes of recurrent respiratory tract infections in children. At present, there is no gold standard for diagnosis. In patients clinically suspected with PCD, a variety of examination methods are available to assist in diagnosis, such as high-speed video microscopic imaging to analyze ciliary movement patterns, transmission electron microscopy to observe ciliary ultrastructure, genetic testing, and detection of nitric oxide content in nasal expiratory air.

Case Description

We present a case summary of the clinical data and treatment process of a child with PCD and short stature induced by Novel exon 1 of CCNO mutation (NM-021147.5) at c.323del, and the proband father and mother were heterozygous mutators, who was diagnosed and treated in the Pediatric Healthcare Department of our hospital. We treated the child with recombinant human growth hormone to increase the height, and the patient was also advised to improve nutrition, prevent and control infections, and encouraged sputum expectoration. We also recommended regular follow-up visits to the outpatient department, and to seek other symptomatic and supportive treatments as necessary.

Conclusion

The height and nutritional status of the child improved after treatment. We also reviewed relevant literature to help clinicians improve their understanding of this disease.

Biallelic Variants in CCDC39 Gene Lead to Primary Ciliary Dyskinesia and Kartagener Syndrome

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.

Patient-specific three-dimensional explant spheroids derived from human nasal airway epithelium: a simple methodological approach for ex vivo studies of primary ciliary dyskinesia

BACKGROUND

Three-dimensional explant spheroid formation is an ex vivo technique previously used in studies of airway epithelial ion and water transport. Explanted cells and sheets of nasal epithelium form fully differentiated spheroids enclosing a partly fluid-filled lumen with the ciliated apical surface facing the outside and accessible for analysis of ciliary function.

METHODS

We performed a two-group comparison study of ciliary beat pattern and ciliary beat frequency in spheroids derived from nasal airway epithelium in patients with primary ciliary dyskinesia (PCD) and in healthy controls. Nasal ciliary cells and sheets were removed on day 1 by nasal brush biopsy and analyzed with regard to ciliary beat pattern-and frequency using high-speed video imaging for standard reference values. Three-dimensional explant spheroid formation was initiated in the same individual on the same day by incubation of cells and sheets from a separate brush biopsy. Harvested spheroids were analyzed earliest possible and values of spheroid ciliary beat pattern and frequency were compared to the corresponding reference values from day 1.

RESULTS

Spheroids formed fast in serum-free culture medium. Formation was successful in 15 out of 18 (82%) sampled individuals. Thus, formation was successful in seven healthy controls and eight PCD patients, while unsuccessful in 3 with PCD due to infection. Median (range) number of days in culture before harvesting of spheroids was 4 (1-5) in healthy versus 2 (1-5) in PCD. Spheroid ciliary beat pattern and frequency were unchanged compared to their corresponding day 1 standard reference values. Spheroid ciliary beat frequency discriminated highly significant between healthy controls (9.3 Hz) and PCD patients (2.4 Hz) (P < 0.0001). Survival of spheroids was 16 days in a single healthy person.

CONCLUSION

Patient-specific three-dimensional explant spheroid formation from a minimal invasive nasal brush biopsy is a feasible, fast and valid ex vivo method to assess ciliary function with potential of aiding the diagnosis of PCD. In addition, it may be a useful model in the investigation of pathophysiological aspects and drug effects in human nasal airway epithelium.

Primary ciliary dyskinesia in two English Cocker Spaniels

BACKGROUND

Primary ciliary dyskinesia (PCD) is an inherited condition characterised by structural and functional defects of ciliated cells. Ciliated cells are present in several different anatomic locations and PCD can thus cause a variety of clinical signs; however, the predominant clinical signs in dogs are respiratory in nature, most commonly chronic nasal discharge and recurrent lower respiratory tract infections commencing in the neonatal period.

CASE REPORT AND CONCLUSION

This report describes two cases of PCD in English Cocker Spaniel puppies presenting with chronic nasal discharge and bronchopneumonia. We describe the use of a minimally invasive technique to collect samples suitable for cilial studies for its diagnosis.

Comparison of conventional pulmonary rehabilitation and high-frequency chest wall oscillation in primary ciliary dyskinesia

BACKGROUND

Enhancement of mucociliary clearance by pulmonary rehabilitation (PR) is advocated in primary ciliary dyskinesia (PCD). Our primary aim was to compare the efficacy and safety of postural drainage, percussion and vibration [conventional PR (CPR)], and high frequency chest wall oscillation (HFCWO) by studying change in pulmonary function. Our secondary aim was to evaluate patient preferences regarding the two methods.

METHODS

This was a controlled randomized crossover study. PCD patients between the ages of 7 and 18 years were assigned to two groups, first group performed airway clearance with CPR at hospital for 5 days and after a 2-day washout period HFCWO was applied to the same group at home. HFCWO was applied first to the other group and then these patients were hospitalized for CPR. The primary outcome measure of the study was pulmonary function test (PFT). The secondary outcomes were pulse arterial oxygen saturation (SpO2 ) and the perceived efficiency and comfort level.

RESULTS

PFT values of patients increased significantly after both PR methods (before/after): CPR: FVC: 77.0 ± 14.1/81.8 ± 13.0 (P = 0.002); FEV1 : 72.9 ± 14.8/78.7 ± 13.5 (P = 0.001); PEF: 73.8 ± 14.5/82.5 ± 14.5 (P = 0.001); FEF25-75 : 68.6 ± 27.6/74.9 ± 29.3 (P = 0.007).

HFCWO FVC

75.1 ± 15.3/80.3 ± 13.9 (P = 0.002); FEV1 : 71.4 ± 16/77.4 ± 14.6 (P = 0.001); PEF: 70.9 ± 18.0/78.3 ± 17.7 (P = 0.002); FEF25-75 : 70.5 ± 23.4/76.4 ± 25.6 (P = 0.006). There were no significant differences in % predicted FVC, FEV1 , PEF, and FEF25-75 increased values with CPR and HFCWO. HFCWO was found more comfortable (P = 0.04). Two PR methods were found efficient and no desaturation occurred during PR.

CONCLUSIONS

PFTs were significantly increased after both PR methods. There were no differences in PFTs and SpO2 between the CPR and HFCWO groups. Both PR methods were found efficient. HFCWO was found more comfortable. HFCWO may be an option in patients with chronic pulmonary disease and low adherence to PR.

Primary ciliary dyskinesia, an orphan disease

Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disease, caused by specific primary structural and/or functional abnormalities of the motile cilia, in contrast with the transitory abnormalities seen in secondary ciliary dyskinesia. Disease-causing mutations in at least 16 genes have already been identified. The true incidence of PCD may be higher than currently reported, because the diagnosis is challenging and often missed. For the confirmation of PCD, both ciliary motility as well as ciliary ultrastructure must be evaluated. An early and adequate diagnosis and therapy can theoretically prevent bronchiectasis. Measurement of nasal nitric oxide has some value as a screening test but cannot be performed in young children. In the respiratory tract epithelium, impaired mucociliary clearance leads to chronic and/or recurrent upper and lower respiratory tract infections. In up to 75 % of the patients, respiratory manifestations start in the newborn period, although the diagnosis is often missed at that time. During embryogenesis, nodal cilia, which are motile cilia, determine the correct lateralization of the organs. Dysfunction of these cilia leads to random lateralization and thus situs inversus in approximately 50 % of the patients with PCD. The tail of a spermatozoon has a structure similar to that of a motile cilium. Consequently, male infertility due to immotile spermatozoa is often part of the characteristics of PCD. Given the heterogeneity and the rarity of the disorder, therapy is not evidence-based. Many treatment schedules are proposed in analogy with the treatment for cystic fibrosis.

CONCLUSION

Respiratory infections, situs inversus and male infertility are typical manifestations of PCD, a rare autosomal recessive disorder.

A sperm viability test using SYBR-14/propidium iodide flow cytometry as a tool for rapid screening of primary ciliary dyskinesia patients and for choosing sperm sources for intracytoplasmic sperm injection

Spermatozoa viability tests based on dual-color flow cytometry after staining with Sybr-14/propidium iodide were performed on 44 men with complete asthenospermia for primary ciliary dyskinesia (PCD) screening, and seven were identified with PCD by electron microscopy of ultrastructural ciliary defects. Six PCD patients underwent eight intracytoplasmic sperm injection therapy cycles using ejaculated sperm or testicular sperm, obtaining a mean fertilization rate of 46.6%, with three healthy babies born and one in utero at the time of writing.

Characteristics of chloride transport in nasal mucosa from patients with primary ciliary dyskinesia

OBJECTIVES/HYPOTHESIS

Primary ciliary dyskinesia (PCD) is an inherited disorder that produces lifelong difficulties with chronic airway inflammation. Little is known about the role of chronic airway inflammation on chloride ion transport properties in PCD. This study assessed the cyclic adenosine monophosphate (cAMP)-regulated chloride (Cl) ion transport properties of freshly excised nasal mucosa from PCD compared with normal and chronic rhinosinusitis (CRS).

STUDY DESIGN

Electrophysiology study utilizing Ussing type hemi-chamber technique with three different types of nasal tissue (normal, CRS, PCD) obtained from patients during endoscopic surgery at a tertiary referral center.

METHODS

Nasal tissues were examined under short-circuit conditions, and gradient-driven Cl currents were continuously recorded. The cAMP elevating agonist (forskolin) was added to stimulate cystic fibrosis transmembrane conductance regulator-mediated Cl secretion. To prevent misinterpretation of flux measurement, Cl transport inhibitors were used at the end of all experiments. Basal Cl currents (I(Cl)) and changes in I(Cl) to forskolin (DeltaI(Cl)) were compared between normal, CRS, and PCD nasal tissues.

RESULTS

Forskolin stimulated Cl currents across all different types of nasal epithelia. The Cl secretory response was effectively blocked by the Cl ion transport inhibitors. I(Cl) were significantly higher in normals (155.0 +/- 9.3 microA/cm(2)) compared to CRS (79.1 +/- 15.0 microA/cm(2)) and PCD (70.9 +/- 20.4 microA/cm(2)) (P = .005). DeltaI(Cl) in CRS (14.8 +/- 2.3 microA/cm(2)) and PCD (12.2 +/- 2.4 microA/cm(2)) were markedly diminished compared to normals (28.3 +/- 4.7 microA/cm(2)) (P = .024).

CONCLUSIONS

PCD tissues were characterized by impaired I(Cl) and DeltaI(Cl). Both parameters were reduced by 54.3% and 56.9% in PCD when compared to normals.

The genetic basis of male reproductive failure

Evolving therapies have allowed the use of sperm from men with spermatogenic compromise, obstructive azoospermia, and sperm functional deficiency, enabling these men to procreate when unable to do so naturally. The genetic basis of only a portion of these conditions is known and research must be pursued into the genetic underpinnings of those that have not yet been delineated. Education and provision of information to patients is the responsibility of all involved in the care of men with reproductive failure. The author concentrates on some of the known causes of nonobstructive azoospermia and obstructive azoospermia with a well-established genetic cause such as congenital bilateral absence of the vas deferens.