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Primary ciliary dyskinesia (PCD) is a rare respiratory disease characterized by chronic bronchorrhea with bronchiectasis and chronic sinusitis. PCD is the second most frequent congenital affection of the respiratory tract after cystic fibrosis. The prevalence of PCD is estimated at 1/20,000. Clinical signs can appear at birth with respiratory failure syndrome. During childhood, the disease manifests with cough and chronic bronchorrhea, chronic rhinitis with nasal polyposis, frontal sinus agenesis and recurrent otitis. An association with situs inversus occurs in nearly 50% of the cases and constitutes the Kartagener syndrome (KS; see this term). Cardiac anomalies, such as atrial septal defect or transposition of the great vessels (see these terms), can be present. Ciliary defects result in altered mucociliary transport in the respiratory tract. They may also affect the flagella of the spermatozoa, causing infertility in males. Various structural abnormalities such as dynein arm deficiency, radial spoke deficiency or peripheral microtubule transposition have been described. PCD is a recessively inherited disorder. Mutations of genes DNAH5 (28% of patients), DNAI1 (2-10% of patients), TXNDC3, DNAH11, and DNAI2 (more rarely found), encoding components of the outer dynein arm (ODA) that generate cilia and flagella movement, can cause PCD. Mutations in the DNAI1 or DNAH5 genes account for approximately one third of PCD/KS cases. Other genes have been recently implicated in PCD: C14orf104, OFD1, RSPH9, and RSPH4A. A rare form of PCD associated with retinitis pigmentosa is caused by a mutation in the RPGR gene. Families in which transmission of PCD is autosomal dominant have been described, but the gene involved has not been identified. Infertility is one of the situations leading to diagnosis of the disease in males. The saccharin inhalation test is informative but not suitable for young children, as the tested patient has to keep still. As a consequence, biopsy or brushing of the ciliary mucosa, which should be performed in specialized centers, is usually required to assist the diagnosis. It allows ciliary function to be assessed by measurements of ciliary beat frequency and allows cilia structure to be analyzed by electron microscopy. Recording the ciliary beat with a high-speed digital camera is possible and allows visualization of the ciliary beat in slow motion. This is likely to become a reference test in the future. The differential diagnosis should include cystic fibrosis (see this term) and immunodeficiency. Management is symptomatic. Regular vaccinations and early antibiotic treatments, together with respiratory physiotherapy in case of respiratory infections, help to limit the development of bronchiectasis. Daily pulmonary physiotherapy is necessary in patients with bronchiectasis, even during the quiescent periods. In patients with end-stage respiratory failure, pulmonary transplantation may be proposed. Surgery is sometimes necessary to correct congenital cardiac anomalies. The prognosis of the disease depends on the recurrence of pulmonary infections, as they most often lead to bronchiectasis with chronic respiratory failure. |