What Is Gardners Syndrome Causes Symptoms Risks?

Gardner syndrome is a rare genetic disorder that causes hundreds to thousands of polyps to grow in the colon and rectum, almost always leading to colorectal cancer by age 40 if untreated. It is a severe form of familial adenomatous polyposis (FAP), caused by a mutation in the APC gene. People with Gardner syndrome also develop non-cancerous growths in bones, skin, and soft tissues, which often appear before the colon polyps do. Early diagnosis and surgical removal of the colon are the only ways to prevent cancer.

What Exactly Causes Gardner Syndrome?

Gardner syndrome is caused by a specific mutation in the APC gene on chromosome 5. This gene normally tells your body to make a protein that stops tumors from growing. When the gene is broken, that protection is lost.

The mutation is inherited in an autosomal dominant pattern. That means if one parent has the mutated gene, each child has a 50 percent chance of inheriting it. About 20 to 30 percent of cases are new mutations with no family history at all. As of 2026, genetic testing can identify the specific APC mutation in most families.

It is important to understand that Gardner syndrome is not a separate disease from FAP. It is simply a variant of FAP that happens to include extra-colonic growths like bone tumors and skin cysts. The colon cancer risk is the same: nearly 100 percent without surgery.

What Are the First Symptoms of Gardner Syndrome?

The earliest symptoms are often not in the colon. Many people first notice hard, non-painful lumps on their jaw or skull. These are called osteomas and they are benign bone growths. Another early sign is multiple sebaceous cysts on the skin, especially on the scalp, face, and back.

Dental abnormalities are also common. Supernumerary teeth (extra teeth), impacted teeth, and odontomas (benign tooth-related tumors) can appear in childhood or adolescence. A dentist may be the first doctor to suspect Gardner syndrome.

Colon symptoms usually start later, around age 15 to 20. These include rectal bleeding, chronic diarrhea, abdominal pain, and unexplained weight loss. By this time hundreds of polyps are already present.

How Is Gardner Syndrome Diagnosed and What Are the Risks?

Diagnosis begins with a colonoscopy to look for polyps. In Gardner syndrome, the colon is carpeted with hundreds to thousands of adenomatous polyps, not just a few. The sheer number is a key clue.

Genetic testing confirms the diagnosis. A blood test looks for the APC gene mutation. If the mutation is found, immediate screening for family members is recommended. Current research suggests that genetic testing should be offered to all first-degree relatives of anyone diagnosed with Gardner syndrome.

The risks are serious and specific. Colorectal cancer is the biggest threat. Without surgical removal of the colon, cancer almost always develops by age 40. There is also an increased risk for other cancers including thyroid cancer, stomach cancer, small bowel cancer, and hepatoblastoma (a rare liver cancer in children). Desmoid tumors, which are non-cancerous but locally aggressive growths in the abdominal wall, occur in about 10 to 15 percent of patients and can be difficult to treat.

How Is Gardner Syndrome Treated?

Surgery is the main treatment for the colon polyps. The standard procedure is a total colectomy with ileorectal anastomosis, where the colon is removed but the rectum is left. An alternative is a proctocolectomy with ileal pouch-anal anastomosis, which removes both the colon and rectum and creates an internal pouch from the small intestine.

Which surgery is chosen depends on how many polyps are in the rectum and the patient’s personal preferences. After surgery, regular surveillance of the remaining rectum or pouch is still needed because polyps can grow there too.

Non-steroidal anti-inflammatory drugs (NSAIDs) like sulindac and celecoxib have been shown to reduce the number and size of polyps in some patients. Some studies suggest these drugs can delay the need for surgery in certain cases. However, they do not eliminate cancer risk and are not a replacement for surgery. As of 2026, current research suggests that NSAID use should be considered an adjunct, not a primary treatment.

Desmoid tumors are tricky. Some grow slowly and need no treatment. Others grow aggressively and require surgery, radiation, or medication. There is no single best approach, and treatment is individualized.

What Surveillance Is Needed for Gardner Syndrome?

Surveillance starts early and is lifelong. Children at risk should have a colonoscopy starting at age 10 to 12, repeated every year if polyps are found. Upper endoscopy to check the stomach and duodenum should begin by age 20 to 25.

Thyroid ultrasound is recommended every year starting in the teenage years. Abdominal ultrasound may be done to check for hepatoblastoma in young children. Physical exams for skin cysts and bone growths are part of routine care.

Family members who test negative for the APC mutation do not need any special surveillance beyond standard cancer screening. This is a relief for many families. Genetic testing clarifies who truly needs intensive monitoring and who does not.

• Colonoscopy: Start at age 10-12, repeat annually
• Upper endoscopy: Start at age 20-25, repeat every 1-3 years
• Thyroid ultrasound: Start in teenage years, repeat annually
• Abdominal ultrasound: For children under 5, to check for hepatoblastoma
• Dental exams: Regular checkups for extra teeth and jaw growths

Common Misconceptions About Gardner Syndrome

One widespread myth is that Gardner syndrome is a different disease from FAP. It is not. It is the same genetic condition with extra features. The colon cancer risk is identical.

Another misconception is that removing the polyps one by one during colonoscopy is a viable long-term strategy. It is not. By the time polyps are visible, there are too many to remove individually. Surgery is the only reliable option.

Some people believe that if they have no family history, they cannot have Gardner syndrome. This is false. New mutations account for up to 30 percent of cases. Anyone with hundreds of colon polyps and no family history should still be tested.

Finally, there is a belief that desmoid tumors are cancerous. They are not. They are benign growths that do not spread to other parts of the body. However, they can be locally invasive and cause serious problems by pressing on organs or blood vessels.