To the Editor: We appreciate the comments of Rosenberg et al. in their letter, “Runs of Homozygosity and Parental Relatedness,”1 as they provide important points regarding the complex origins of runs of homozygosity. We agree that the percentage of the genome consisting of homozygous segments varies across different ethnic populations and that the best estimates of parental relatedness would take this background contribution (both percentage of the genome and size of the homozygous segments) into account; however, this is probably impractical for most clinical laboratories, which frequently receive limited demographic information. The comments by the authors further highlight the complexity of these assessments and reinforce our recommendation that genomic testing that can detect runs of homozygosity should never be used to definitively assign a specific relationship between the parents of a proband.

Disclosure

The authors declare no conflict of interest.