The individual with Lynch syndrome, diagnosed with PC, has a familial heterozygous mutation within the MSH6 gene (c.3939_3957dup19, Genbank accession number: NM_0001791) predicted to result in a truncated MSH6 protein product due to premature termination of the open reading frame at position 1324, p.(Ala1320SerfsX5). Here, MSH6 is linked to pachyonychia congenita.