Preimplantation Genetic Testing for Kidney Disease-Related Genes: A Laboratory's Experience.

INTRODUCTION: Recent literature highlights the clinical utility of genetic testing for patients with kidney disease. Genetic testing provides significant benefits for reproductive risk counseling, including the option of in vitro fertilization with preimplantation genetic testing for monogenic disease (PGT-M). PGT-M allows for a significant reduction in risk for a pregnancy affected with the familial disease. We aim to summarize our experience with PGT-M for genes with kidney involvement as either a primary or secondary feature of the disease. METHODS: All PGT-M tests performed by the reference laboratory between September 2010 and July 2020 were reviewed for clinical indication and cases for which the disease tested included a renal component. Each patient referred for PGT-M had an existing molecular genetic diagnosis themselves or in their family. Frequency of each condition, gene, inheritance pattern, and year over year increase in referral cases was analyzed. RESULTS: In the study cohort, the most common disease targeted was autosomal dominant polycystic kidney disease, caused by pathogenic variants in the PKD1 or PKD2 genes, which accounted for 16.5% (64/389) of cases. The 5 most common referral indications accounted for 51.9% (202/389) of the cases. Autosomal recessive inheritance accounted for 52.0% (26/50) of conditions for which PGT-M was performed. The number of PGT-M tests performed for conditions that included either primary or secondary kidney disease increased from 5 cases in 2010 to 47 cases in the 2020 study period. DISCUSSION/CONCLUSION: These data suggest that the pursuit of PGT-M by couples at risk for passing on conditions with a kidney component is common and has significantly increased since 2010. With this rising trend of patients undergoing PGT-M and the prerequisite of molecular genetic confirmation in the PGT-M process, this study underscores the importance of the reproductive component to a molecular genetic diagnosis for patients with kidney disease, especially as the accessibility of genetic testing and utilization by nephrologists grows.

Estimating the relative frequency of leukodystrophies and recommendations for carrier screening in the era of next-generation sequencing.

Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A-related leukodystrophy, Peroxisomal biogenesis disorders, POLR3-related Leukodystrophy, Vanishing White Matter, and Pelizaeus-Merzbacher Disease. Despite the relative frequency of these conditions, carrier-screening laboratories regularly test only 20 of the 55 leukodystrophy-related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.