In our practice we have never seen a case of Gardner Syndrome – at least any that we have been aware of (J Oral Maxillofac Surg 77:1617-1627, 2019)  Gardner Syndrome is characterized by uncountable adenomas throughout the colon and rectum, with a high risk of developing colorectal cancer (CRC). If left untreated it has almost 100% penetrance. The syndrome also is characterized by extraintestinal manifestations, such as osteomas, odontomas, supernumerary teeth, impacted teeth, and a multitude of soft tissue tumors, including lipomas, fibromas, epidermoid cysts, and desmoids. A simple dominant mechanism of inheritance has been implicated. It is caused by a mutation in the adenomatous polyposis coli (APC) gene, located on chromosome 5q21. Mutations of the APC gene result in a protein product that loses the ability to degrade beta-catenin, which in turn promotes fibroblastic proliferation. What this means is that the body can produce various abnormally excessive tissues which include benign growths – such as we see in the mouth with multiple bony projections on the jaws (exostosis or “tori”) – typically small, round, raised, tissue covered “bumps.”

Exostoses appear normally in the general population. About 15% of all groups have these in varying amounts. Some people have a few small ones, some have many and/or large ones.

What I have observed over time is what I believe to be a partial penetrance of the gene expression. We have seen a number of patients who show the multiple osteomas/exostoses who also show a family history of colon cancer. The truth is that this may just be a coincidence as they may fall into the normal 15% of the overall population. But anecdotally, I have observed that those patients where we have seen the two things together – colorectal cancer and a history of multiple exostoses – the exostoses are more significant in size, number, and location.

For me, in my practice, I just observe and report when I see multiple exostoses. I will ask about family history for colorectal cancer and I will advise the patient about the possible relationship. This is informational, is presented in a non-alarming way, and could help to make an early diagnosis of a potentially serious condition.