Familial colorectal cancer and tooth agenesis caused by an AXIN2 variant: how do we detect families with rare cancer predisposition syndromes?

We present a three-generation family with an AXIN2 variant and a family history of colorectal cancer (CRC), colon polyps and tooth agenesis. A likely pathogenic variant was detected in the AXIN2 gene (c.1994dup; p.(Asn666Glnfs*41)). This variant has previously been associated with tooth agenesis and polyposis, only. In this case report we describe eight carriers with tooth agenesis and variable clinical findings, including polyps and CRC. Our case provides additional knowledge to the sparse data on genotype-phenotype association related to AXIN2 associated cancer syndrome. Further, our case highlights the importance of analysing an extended CRC and oligodontia/ectodermal dysplasia gene panel including AXIN2 but also raises awareness and discussion about appropriate surveillance program.