Primary ciliary dyskinesia (PCD) is a rare disorder of immotile or abnormally motile cilia resulting in chronic recurrent respiratory infection, sinusitis, otitis media, and male infertility due to abnormal sperm motility. Incidence is approximately 1 in 20,000 individuals. Often familial, PCD demonstrates an autosomal recessive pattern of inheritance. Onset of symptoms is usually in childhood. Half of cases are associated with situs inversus (Kartagener syndrome), which may be a clue to diagnosis. Situs inversus results from abnormal ciliary motility in the embryonic node, which determines left-right asymmetry. Chronic headaches and hydrocephalus in some PCD patients are thought to result from impaired ciliary movement of the ventricular ependymal lining cells, and therefore abnormal cerebrospinal fluid flow. The major pulmonary complications of PCD result from impaired mucociliary clearance, leading to mucus stasis, chronic bronchitis, bronchiectasis, and chronic recurrent parenchymal infections. Histologic findings in the lung include mucus stasis, bronchiectasis, lymphocytic bronchitis and bronchiolitis, peri-airway fibrosis, and variable bronchopneumonia.

Biopsies of the tracheobronchial mucosa or nasal mucosa are often performed for screening of ciliary motility. Although there is no role for routine processing and light microscopy of tracheal or endobronchial biopsies in this setting, immediate direct wet mount preparations of brushings or biopsies are performed for evaluation of ciliary movement. The cilia are evaluated by assessing the presence or absence of coordinated movement, normally showing a rhythmic wavelike motion with each beat. Presence of squamous metaplasia or inflammation may cause secondary impairment or absence of ciliary movement, and detection of these features on direct microscopy may necessitate repeat biopsy at a different site or time. If the specimen is adequate and no ciliary movement is detected, ultrastructural examination is then performed to identify any structural abnormalities in the ciliary apparatus. The normal arrangement of microtubules in the ciliary axoneme includes 9 peripheral microtubule doublets interconnected by nexin links and 2 central individual microtubules (9 + 2 arrangement), which are connected to the peripheral doublets by radial spokes. Defects in any of these axonemal structures may occur, although the absence or truncation of outer and/or inner dynein arms is most frequently recognized in PCD patients.