Search

Purpose: Exome sequencing (ES) could detect pathogenic variants that are unrelated to the test indication, including findings that may have an impact for patients considering conception/reproduction (reproduction-related findings [RRFs]), deliberately searched secondary findings (SFs), and incidental findings (IFs). We aimed to examine the detection rate of clinically actionable findings and to present counseling dilemmas in 840 parents of probands undergoing clinical trio ES testing. Methods: RRFs/IFs/SFs were actively searched for in the parents as part of ES data analysis. Variants were filtered by frequency, mode of inheritance, ClinVar classification, presence in local pathogenic variant databases, and protein-truncating effect. Results: In 14 of 420 families (3.3%), 15 RRFs were detected. Shared parental heterozygous status for autosomal recessive disorders was identified in 23.3% of consanguineous and 1.8% of nonconsanguineous couples. SFs were found in 22 of 840 individuals (2.6%), including 15 variants (7 founder variants) in cancer-predisposing genes and 4 in cardiac disease–related genes. IFs were found in 3 individuals without reported symptoms. Overall, variants of potential medical importance were detected in 9.3% of families. Challenges related to the decision whether to report variants included unreported parental phenotype, presymptomatic testing, variable disease expressivity, potential medical implications for children who are already born, and medicolegal aspects. Conclusion: Active search for RRFs, IFs, and SFs yields a high rate of findings, which may contribute to individual medical care in parents of probands undergoing ES. A structured approach to overcome the challenges associated with reporting these findings should be considered before such an active search can be broadly adopted in clinical genomic data analysis.

The role of lysine methyltransferases (KMTs) and demethylases (KDMs) in the regulation of chromatin modification is well-established. Recently, deleterious heterozygous variants in KMT5B were implicated in individuals with intellectual disability (ID) and/or autism spectrum disorder. We describe three unrelated patients with global developmental delay (GDD) or ID, macrocephaly and additional features. Using whole exome sequencing, each of the probands was found to harbor a distinct de novo heterozygous disease-causing variant in KMT5B: c.541C > G (p.His181Asp); c.833A > T (p.Asn278Ile); or c.391_394delAAAG (p.Lys131GlufsTer6). We discuss herein their clinical presentations, and compare them to those of previously reported patients. Furthermore, using a three-dimensional computational model of the KMT5B protein, we demonstrate the predicted structural effects of the two missense variants. Our findings support the role of de novo missense and nonsense variants in KMT5B-associated GDD/ID, and suggest that this gene should be considered in the differential diagnosis of neurodevelopmental disorders accompanied by macrocephaly and/or overgrowth.