Abstract
Primary ciliary dyskinesia (PCD) is an orphan disease (MIM 244400), autosomal recessive inherited, characterized by motile ciliary dysfunction. The estimated prevalence of PCD is 1:10,000 to 1:20,000 live-born children, but true prevalence could be even higher. PCD is characterized by chronic upper and lower respiratory tract disease, infertility/ectopic pregnancy, and situs anomalies, that occur in ≈50% of PCD patients (Kartagener syndrome), and these may be associated with congenital heart abnormalities. Most patients report a daily year-round wet cough or nose congestion starting in the first year of life. Daily wet cough, associated with recurrent infections exacerbations, results in the development of chronic suppurative lung disease, with localized-to-diffuse bronchiectasis. No diagnostic test is perfect for confirming PCD. Diagnosis can be challenging and relies on a combination of clinical data, nasal nitric oxide levels plus cilia ultrastructure and function analysis. Adjunctive tests include genetic analysis and repeated tests in ciliary culture specimens. There are currently 33 known genes associated with PCD and correlations between genotype and ultrastructural defects have been increasingly demonstrated. Comprehensive genetic testing may hopefully screen young infants before symptoms occur, thus improving survival. Recent surprising advances in PCD genetic designed a novel approach called “gene editing” to restore gene function and normalize ciliary motility, opening up new avenues for treating PCD. Currently, there are no data from randomized clinical trials to support any specific treatment, thus, management strategies are usually extrapolated from cystic fibrosis. The goal of treatment is to prevent exacerbations, slowing the progression of lung disease. The therapeutic mainstay includes airway clearance maneuvers mainly with nebulized hypertonic saline and chest physiotherapy, and prompt and aggressive administration of antibiotics. Standardized care at specialized centers using a multidisciplinary approach that imposes surveillance of lung function and of airway biofilm composition likely improves patients’ outcome. Pediatricians, neonatologists, pulmonologists, and ENT surgeons should maintain high awareness of PCD and refer patients to the specialized center before sustained irreversible lung damage develops. The recent creation of a network of PCD clinical centers, focusing on improving diagnosis and treatment, will hopefully help to improve care and knowledge of PCD patients.
Highlights
Primary ciliary dyskinesia (PCD) is a clinically and genetically heterogeneous group of disorders of ciliary motility (MIM 244400) [1]
In most cases of PCD, inheritance is autosomal recessive, but X-linked PCD caused by mutations in RPGR gene, which is responsible for 20% of all cases with retinitis pigmentosa, or in PIH1D3 gene have been reported [2,3,4]
History of PCD starts with Kartagener who first described a syndrome that included the triad of chronic sinusitis, bronchiectasis, and situs viscerum inversus (SI) [5]
Summary
Primary ciliary dyskinesia (PCD) is a clinically and genetically heterogeneous group of disorders of ciliary motility (MIM 244400) [1]. Sperm tails and respiratory cilia lacked dynein arms and showed impaired motility. This report clarified that a congenital defect in cilia and sperm tails can result in the association of chronic respiratory tract infections and male sterility, and the term “immotile-cilia syndrome” was eventually coined [7]. The nodal cilia play a vital role in establishing left–right body orientation, and abnormalities can lead to laterality defects that include SI and a spectrum of situs ambiguous condition, that may be associated with congenital heart abnormalities [13]. In 2010, Kuehni et al conducted the largest international survey of pediatric PCD patients ever undertaken, which included 1,192 patients from 26 European countries [16] They concluded that the prevalence of diagnosis ranged from 1:10,000 to 1:20,000 live-born children. In order to systematically collect data on PCD incidence, clinical presentation, and treatment, a registry was launched in January 2014, that provides epidemiological data and clinical information of 201 patients with PCD from several European and North-American centers [21]
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