Identity-by-descent analysis of CMTX3 links three families through a common founder.

A large 78 kb insertion from chromosome 8q24.3 into Xq27.1 was identified as the cause of CMTX3 in three families of European descent from Australia (CMT193, CMT180) and New Zealand/United Kingdom (CMT623). Using the relatedness tool XIBD to perform genome-wide identity-by-descent (IBD) analysis on 16 affected individuals from the three families demonstrated they all share the CMTX3 disease locus identical-by-descent, confirming the mutation arose in a common ancestor. Relationship estimation from IBD segment data has genetically linked all three families through 6th and 7th degree relatives.