Primary ciliary dyskinesia (PCD) is a disorder of immotile or abnormally motile cilia resulting in symptoms of chronic recurrent respiratory infection, sinusitis, and otitis media, usually with onset in childhood. Male infertility results from abnormal sperm motility, and accounts for late presentation of PCD in some cases. Situs inversus (Kartagener syndrome) is associated in approximately one-half of cases, due to abnormal ciliary motility in the embryonic node determining left-right asymmetry. Chronic headaches and hydrocephalus are well described in PCD, and are thought to result from abnormal cerebrospinal fluid flow due to impaired motility of ependymal cilia lining the cerebral ventricles. PCD is rare, estimated to affect approximately 1 in 20,000 individuals, but recognized in only a minority of cases. It is often a familial disease with an autosomal recessive inheritance pattern.

Defects in the ciliary apparatus in PCD result in impairment of normal mucociliary clearance of infectious agents and debris from the airways, leading to mucus stasis, chronic bronchitis, bronchiectasis, and chronic parenchymal infections. Regional fibrosis and chronic inflammation of the lung evolves from recurrent and persistent infections. PCD should be considered in the differential diagnosis of bronchiectasis in a child, in addition to cystic fibrosis, primary immunodeficiency, and other specific causes of airway obstruction.

Screening for appropriate rhythmic ciliary motility may be performed on immediate direct wet mount preparations of biopsies or brushings from the nasal cavity, sinuses, or tracheobronchial tree. Causes of secondary (acquired) ciliary dyskinesia should be considered in diagnosis. Ultrastructural examination is necessary to identify structural abnormalities in the ciliary apparatus, typically absence or truncation of the outer and/or inner dynein arms. The arrangement of microtubules in the ciliary axoneme may also be altered from the usual 9 peripheral microtubule doublets and 2 central individual microtubules (9 + 2 arrangement). Defects in the radial spokes that connect the central microtubules to the peripheral microtubules have also been reported.