Primary Ciliary Dyskinesia: A Review

Abstract

Primary ciliary dyskinesia (PCD) is a disease involving the cilia of the body. First identified as Kartagener’s syndrome (a constellation of findings of chronic sinusitis, bronchiectasis, and situs inversus), the genetic basis has been increasingly uncovered over time. It is now recognized as an autosomal recessive condition due to a mutation in one of several dozen genes, and more is still being discovered as we continue to have ever-expanding access to genetic sequencing technology. These mutations can affect different parts of the creation, structure, or effector mechanisms of the cilia, with the common result being the impairment of ciliary function. Thus, the primary pathology in PCD is immotile or reduced motility of the cilia in various organs, which leads to the principal manifestation of impaired muco-ciliary clearance in the respiratory tract. These cilia are responsible for the constant movement of mucus upwards, often termed the muco-ciliary escalator, to prevent mucus stasis and eliminate the natural collection of airway debris. When this fails, it provides a nidus for bacterial growth, leading to both chronic bacterial colonization and acute bacterial respiratory exacerbations, defined as an acute worsening of respiratory symptoms. In relation to other manifestations, rotary cilia play a role in embryonal development and lateralization of the organs; hence the possibility of situs inversus/ambiguus developing in PCD. Normal ciliary movement is also required for spermatozoan motility, leading to infertility in males with PCD; females can also experience impaired fertility and higher rates of ectopic pregnancy due to reduced ciliary function in the fallopian tubes.