Ciliary beat pattern and frequency in genetic variants of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a rare genetic disorder leading to recurrent respiratory tract infections. High-speed video-microscopy analysis (HVMA) of ciliary beating, currently the first-line diagnostic tool for PCD in most centres, is challenging because recent studies have expanded the spectrum of HVMA findings in PCD from grossly abnormal to very subtle. The objective of this study was to describe the diversity of HVMA findings in genetically confirmed PCD individuals. HVMA was performed as part of the routine work-up of individuals with suspected PCD. Subsequent molecular analysis identified biallelic mutations in the PCD-related genes of 66 individuals. 1072 videos of these subjects were assessed for correlation with the genotype. Biallelic mutations (19 novel) were found in 17 genes: DNAI1, DNAI2, DNAH5, DNAH11, CCDC103, ARMC4, KTU/DNAAF2, LRRC50/DNAAF1, LRRC6, DYX1C1, ZMYND10, CCDC39, CCDC40, CCDC164, HYDIN, RSPH4A and RSPH1. Ciliary beat pattern variations correlated well with the genetic findings, allowing the classification of typical HVMA findings for different genetic groups. In contrast, analysis of ciliary beat frequency did not result in additional diagnostic impact. In conclusion, this study provides detailed knowledge about the diversity of HVMA findings in PCD and may therefore be seen as a guide to the improvement of PCD diagnostics.