Gardner’s syndrome is a rare inherited condition that causes hundreds of polyps to grow in the colon and rectum, along with unusual growths in bones, skin, and soft tissues throughout the body. It is a subtype of familial adenomatous polyposis (FAP), sharing the same underlying genetic cause but producing a wider range of symptoms beyond the intestines. Without treatment, the colon polyps carry a very high risk of becoming cancerous, which makes early detection and ongoing monitoring critical.
How Gardner’s Syndrome Relates to FAP
Familial adenomatous polyposis is a group of conditions caused by mutations in a single gene. Gardner’s syndrome is one phenotypic variant of FAP, meaning it stems from the same genetic defect but shows up differently in the body. Both conditions produce numerous polyps along the intestinal lining. What sets Gardner’s syndrome apart is the combination of colon polyps with bone tumors called osteomas, skin and soft tissue growths, and sometimes abnormalities in the layer of cells lining the back of the eye.
Other variants of FAP caused by the same gene include Turcot syndrome (linked to brain tumors) and attenuated forms with fewer polyps. Gardner’s syndrome is distinguished by its broader pattern of growths outside the digestive tract.
The Genetic Cause
Gardner’s syndrome is caused by mutations in the APC gene, which normally produces a protein that helps regulate cell growth. When this gene is mutated, the protein gets cut short and can’t do its job. Without a functioning version of this protein, cells divide more freely than they should, leading to the formation of polyps, bone growths, and soft tissue tumors.
The condition follows an autosomal dominant inheritance pattern. That means inheriting just one copy of the mutated gene from either parent is enough to cause the syndrome. Each child of an affected parent has a 50% chance of inheriting the mutation. In some cases, the mutation appears for the first time in a person with no family history, but this is less common.
Colon Polyps and Cancer Risk
The hallmark of Gardner’s syndrome is the development of hundreds, sometimes thousands, of adenomatous polyps in the colon and rectum. These polyps typically begin appearing around age 16 on average, though the exact timing varies. Individually, each polyp carries a small risk of turning cancerous. But with so many present, the cumulative risk becomes enormous. If the colon is left in place and untreated, nearly all patients will eventually develop colorectal cancer.
This is why regular screening begins early, often in the teenage years or even before, for anyone known to carry the gene mutation. Colonoscopy allows doctors to monitor the number, size, and characteristics of polyps over time. When polyps become too numerous to manage through surveillance alone, preventive removal of the colon is typically recommended.
Bone and Dental Growths
Osteomas, which are benign bony lumps, are one of the most recognizable features of Gardner’s syndrome. They commonly develop in the jaw and skull but can appear in other bones as well. These growths are painless in many cases, though jaw osteomas can occasionally interfere with chewing or cause facial asymmetry if they become large enough.
Dental abnormalities are also common. People with Gardner’s syndrome may develop extra teeth (called supernumerary teeth), impacted teeth, or odontomas, which are disorganized clusters of tooth-like material in the jaw. A dentist or oral surgeon who notices these findings in a young patient, especially alongside other unusual growths, may be the first to raise suspicion of the condition.
Skin and Soft Tissue Tumors
Gardner’s syndrome frequently produces growths in the skin and soft tissues. Epidermal cysts, which are firm, round lumps under the skin, can appear at any age. Subcutaneous fibromas (fibrous tissue growths) and lipomas (fatty lumps) are also seen. While none of these are cancerous, they can be bothersome depending on their size and location.
A more serious soft tissue complication is the desmoid tumor. These are dense, fibrous growths that don’t spread to other parts of the body but can be locally aggressive, pressing into surrounding organs and tissues. Desmoid tumors develop in roughly 17% to 29% of people with Gardner’s syndrome. They most often grow in the abdomen, particularly in tissue near the intestines, and can sometimes complicate surgical recovery. Managing desmoid tumors requires careful monitoring and, in some cases, additional treatment to control their growth.
How It’s Diagnosed
Diagnosis typically involves a combination of clinical findings and genetic testing. A doctor may suspect Gardner’s syndrome when a patient presents with multiple colon polyps alongside osteomas, skin cysts, or dental abnormalities. Family history plays an important role, since the condition runs in families with a clear inheritance pattern.
Genetic testing for APC gene mutations can confirm the diagnosis. This is particularly valuable for family members of someone already diagnosed, since identifying carriers before symptoms appear allows screening and prevention to begin early. If a specific mutation is identified in one family member, targeted testing can determine whether relatives carry the same change.
Treatment and Long-Term Management
Because the colon polyps will almost certainly become cancerous over time, preventive surgery to remove the colon is the cornerstone of treatment. The timing depends on the number and progression of polyps. Some patients with a particularly aggressive form of the mutation, such as those with changes at a specific location on the gene called codon 1309, may need surgery earlier, sometimes in childhood or adolescence.
After the colon is removed, a surgeon typically creates an internal pouch from the small intestine that connects to the rectum, allowing relatively normal bowel function. This pouch still requires yearly screening with a scope, because adenomatous changes can develop there as well.
Beyond the colon, managing Gardner’s syndrome means addressing the full range of growths the condition produces. Osteomas that cause discomfort or cosmetic concerns can be surgically removed. Skin cysts and fibromas are treated on a case-by-case basis. Desmoid tumors need careful surveillance and, if they grow into surrounding structures, may require intervention. Patients benefit from coordinated care across multiple specialties, including gastroenterology, surgery, dermatology, and oral surgery, often for the rest of their lives.
Living With Gardner’s Syndrome
Gardner’s syndrome is a lifelong condition that requires consistent follow-up. After preventive colon surgery, the immediate cancer risk drops significantly, but ongoing screening remains essential. The various extra-intestinal growths may continue to develop over time, so regular check-ups with the relevant specialists are part of the routine.
For families affected by the condition, genetic counseling can help clarify risks for children and other relatives. Early identification of gene carriers gives people the chance to begin screening well before polyps or other complications reach a dangerous stage. Many people with Gardner’s syndrome lead full, active lives with appropriate monitoring and timely treatment of complications as they arise.