Moreover, variants in HYDIN2 may be incorrectly assessed as being present in HYDIN. Although bioinformatic masking of HYDIN2 after SR-NGS reduces the effect of this homology and allows for an increased rate of genetic diagnoses in select cohorts, LR-NGS can overcome all of the challenges presented by this large homology region [32].The proportion of HYDIN variants being causative of PCD may vary in different ethnic groups, however we propose that due to the difficulty in identifying pathogenic HYDIN variants, HYDIN may be an underrepresented cause of PCD in most cohorts. Here, HYDIN2 is linked to primary ciliary dyskinesia.