Weekly issue 2026-W38 ·
The Importance of Familial Co-segregation in the Classification of a Novel PKD1 Variant Associated With Autosomal Dominant Polycystic Kidney Disease
Plain language
Genetic tests sometimes find a gene change of ‘uncertain significance’, which cannot yet be used for decisions. In a large family with 14 affected members over three generations, researchers checked who carried a new PKD1 change and who had ADPKD. The change tracked with the disease, so it was upgraded to ‘likely disease-causing’. That let the family use embryo genetic testing (PGT) in IVF. Testing relatives can turn an unclear result into a usable one.
Clinical note
Family study, index plus 13 relatives across three generations with typical progressive ADPKD. Sanger/NGS (PKD1, PKD2, PKHD1) with MLPA excluding CNVs. Heterozygous PKD1 VUS c.8999G>C p.(Arg3000Pro) present in four affected and absent in one unaffected relative; full-likelihood Bayes factor 96.8 (segregatr) reclassified it as likely pathogenic per Jarvik–Browning and ClinGen 2024, enabling PGT. Practical model for resolving PKD1 missense VUS through segregation plus careful phenotyping.
Question for your next visit
If my genetic result shows a variant of uncertain significance, could testing my relatives help clarify it, and what would that involve for them?