HYDIN in plain sight – Undiscovered Primary Ciliary Dyskinesia in Quebec via the HYDIN gene

This study focuses on a lesser‑known form of primary ciliary dyskinesia (PCD), a rare disease affecting the sinuses, ears, and lungs. A gene called HYDIN, once believed to be an extremely rare cause of PCD, appears to be particularly relevant in Quebec. Several patients followed at the specialized PCD clinic of the McGill University Health Centre (MUHC) carry the same HYDIN variant, suggesting a founder effect within the Quebec population.
Because HYDIN‑related PCD does not show the typical abnormalities visible under electron microscopy, many cases remain undiagnosed. However, affected individuals consistently present abnormally low nasal nitric oxide levels, a key biomarker for PCD.
The project uses genetic and genealogical data from CARTaGENE and BALSAC to reconstruct a shared haplotype among HYDIN variant carriers and identify potential carriers in the Quebec population. Genealogy analyses for this HYDIN founder variant, as well as for another founder variant in the TTC25 gene, have now been completed. Two articles based on these results are currently in preparation.
These findings will help estimate the true frequency of the HYDIN variant in Quebec and improve diagnostic strategies, prioritizing effective and less invasive testing approaches for individuals at risk of HYDIN‑associated PCD.

• Chronic diseases
• Genetics and genomics

• Biological samples
• Genetic data
• Physical and cognitive measures
• Questionnaire data