Katrin Õunap

Background Pathogenic variants in AXIN2 have been associated with tooth agenesis, colon polyps, and colon cancer. Given the rare nature of this phenotype, we set out to collect additional genotypic and phenotypic information. Methods Data were collected via a structured questionnaire. Sequencing was performed in these patients mostly due to diagnostic purpose. A little more than half of the AXIN2 variant carriers were identified by NGS; other six were family members. Results Here, we report 13 individuals with a heterozygous AXIN2 pathogenic/likely pathogenic variant who have a variable expression of oligodontia‐colorectal cancer syndrome (OMIM 608615) or oligodontia‐cancer predisposition syndrome (ORPHA 300576). Three individuals from one family also had cleft palate, which might represent a new clinical feature of AXIN2 phenotype, also given the fact that AXIN2 polymorphisms have been found in association with oral clefting in population studies. AXIN2 has already been added to multigene cancer panel tests; further research should be conducted to determine whether it should be added to cleft lip/palate multigene panels. Conclusion More clarity about oligodontia‐colorectal cancer syndrome, about the variable expression, and associated cancer risks is needed to improve clinical management and to establish guidelines for surveillance. We collected information about the surveillance that was advised, which might support clinical management of these patients.