OP-4242II1 was homozygous for an inframe deletion of one amino acid in MNS1 NM_018365.4:c.678_680del; p.(Glu226del) and was affected by situs inversus totalis, while OP-4761II1 was also diagnosed with situs inversus totalis and carried the same variant in a heterozygous state in addition to a heterozygous nonsense variant NM_018365.4:c.1084G>T; p.(Glu362*), resulting in an early stop codon on the other allele (Figure 1C). Here, MNS1 is linked to Situs inversus totalis.