Primary ciliary dyskinesia: recent advances in epidemiology, diagnosis, management and relationship with the expanding spectrum of ciliopathy.

Human cilia were once thought merely to be important in respiratory mucociliary clearance, with primary ciliary dyskinesia (PCD) the sole manifestation of ciliary dysfunction. There are now known to be three types of cilia: primary, nodal and motile. Cilia are complex, likely involving more than 1000 gene products; in this review, recent advances in PCD genetics, and the potential relationships with genes causing other ciliopathies, are discussed. PCD is the most important respiratory disease, characterized by upper and lower airway infection and inflammation and disorders of laterality. Ciliary gene mutations are now known to cause single organ disease, as well as complex syndromes. The focus of the review is primarily PCD, in the context of the expanding ciliopathy spectrum. The authors consider the clinical situations in which ciliary disease should be considered, and the implications for specialist respiratory practice.

Effectiveness of sequencing selected exons of DNAH5 and DNAI1 in diagnosis of primary ciliary dyskinesia.

INTRODUCTION: Primary ciliary dyskinesia (PCD) is a rare genetically heterogenous condition. Mutations in DNAH5 or DNAI1 genes can be found in about a third of the patients with PCD. Increased occurrence of mutations was described in several exons of these long genes. The objective of the study was to test the sensitivity of sequencing of selected 13 exons (as compared to costly sequencing of all 100 exons of the two genes), and to determine the prevalence of the DNAH5 or DNAI1 mutations in the Czech PCD database. METHODS: The Czech national PCD database has identified 31 pediatric patients, diagnosed based on clinical findings and tests on the ciliated epithelium. Twenty-seven patients from 24 families agreed on genetic testing. In the first step, direct sequencing of selected 13 exons (9 of DNAH5 and 4 of DNAI1) was performed, and then we compared its effectiveness in detecting at least one mutation with results of sequencing all 100 exons of the two genes. RESULTS: The sequencing of all exons identified compound heterozygosity for PCD mutations in nine patients from eight families (DNAH5 in eight and DNAI1 in one patient), and heterozygozity for a DNAH5 mutation of uncertain functional significance in one additional patient. The first step of selected exon sequencing detected a mutation in five out of these eight families, its actual sensitivity being 62.5%, with a high predictive value. The phenotypic and clinical characteristics of all the paediatric patients with PCD are shown. CONCLUSIONS: Selected exon sequencing detects at least one mutated allele in over a half of our patients who have PCD due to DNAH5 or DNAI1 mutations. To lower the costs of the genetic testing, targeted step-wise genetic testing may be a reasonable approach to detect mutations in PCD patients, especially if their phenotype is taken into account.