KCNQ1 and Failure to thrive: In contrast, if the recipient is a neonate undergoing diagnostic exome sequencing for failure to thrive, and the donor is heterozygous for a KCNQ1 variant that would predispose to long QT syndrome, the presence of donor DNA may result in a signal; however, again, significant donor DNA would need to be present to reach a level near 50% variant frequency to result in a false positive clinical call.