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Rationale: Primary ciliary dyskinesia (PCD), a genetically heterogeneous, recessive disorder of motile cilia, is associated with distinct clinical features. Diagnostic tests, including ultrastructural analysis of cilia, nasal nitric oxide measurements, and molecular testing for mutations in PCD genes, have inherent limitations.Objectives: To define a statistically valid combination of systematically defined clinical features that strongly associates with PCD in children and adolescents.Methods: Investigators at seven North American sites in the Genetic Disorders of Mucociliary Clearance Consortium prospectively and systematically assessed individuals (aged 0-18 yr) referred due to high suspicion for PCD. The investigators defined specific clinical questions for the clinical report form based on expert opinion. Diagnostic testing was performed using standardized protocols and included nasal nitric oxide measurement, ciliary biopsy for ultrastructural analysis of cilia, and molecular genetic testing for PCD-associated genes. Final diagnoses were assigned as "definite PCD" (hallmark ultrastructural defects and/or two mutations in a PCD-associated gene), "probable/possible PCD" (no ultrastructural defect or genetic diagnosis, but compatible clinical features and nasal nitric oxide level in PCD range), and "other diagnosis or undefined." Criteria were developed to define early childhood clinical features on the basis of responses to multiple specific queries. Each defined feature was tested by logistic regression. Sensitivity and specificity analyses were conducted to define the most robust set of clinical features associated with PCD.Measurements and Main Results: From 534 participants 18 years of age and younger, 205 were identified as having "definite PCD" (including 164 with two mutations in a PCD-associated gene), 187 were categorized as "other diagnosis or undefined," and 142 were defined as having "probable/possible PCD." Participants with "definite PCD" were compared with the "other diagnosis or undefined" group. Four criteria-defined clinical features were statistically predictive of PCD: laterality defect; unexplained neonatal respiratory distress; early-onset, year-round nasal congestion; and early-onset, year-round wet cough (adjusted odds ratios of 7.7, 6.6, 3.4, and 3.1, respectively). The sensitivity and specificity based on the number of criteria-defined clinical features were four features, 0.21 and 0.99, respectively; three features, 0.50 and 0.96, respectively; and two features, 0.80 and 0.72, respectively.Conclusions: Systematically defined early clinical features could help identify children, including infants, likely to have PCD. Clinical trial registered with ClinicalTrials.gov (NCT00323167). [ABSTRACT FROM AUTHOR]

Motile cilia are cellular beating machines that play a critical role in mucociliary clearance, cerebrospinal fluid movement, and fertility. In the airways, hundreds of motile cilia present on the surface of a multiciliated epithelia cell beat coordinately to protect the epithelium from bacteria, viruses, and harmful particulates. During multiciliated cell differentiation, motile cilia are templated from basal bodies, each extending a basal foot—an appendage linking motile cilia together to ensure coordinated beating. Here, we demonstrate that among the many motile cilia of a multiciliated cell, a hybrid cilium with structural features of both primary and motile cilia is harbored. The hybrid cilium is conserved in mammalian multiciliated cells, originates from parental centrioles, and its cellular position is biased and dependent on ciliary beating. Furthermore, we show that the hybrid cilium emerges independently of other motile cilia and functions in regulating basal body alignment. • Multiciliated cells contain a hybrid cilium with features of primary and motile cilium • The hybrid cilium originates from parental centriole • The hybrid cilium position is biased toward the cilia beating direction • The hybrid cilium functions in basal body alignment Liu, Nguyen et al. show that among hundreds of cilia of a multiciliated cell, there is one that differs from the others in structure, origin, and cellular position, and it participates in basal body alignment. [ABSTRACT FROM AUTHOR]