Is Gardner Syndrome Different From FAP? Key Facts Explained

If you have been diagnosed with Gardner Syndrome, you might be confused to see Familial Adenomatous Polyposis (FAP) in your charts. FAP is the inherited condition; Gardner Syndrome is an older label used for FAP when a person also has certain features outside the colon ^[1]. Today, medical professionals understand that both are part of the same spectrum of disease associated with pathogenic variants (mutations) in the exact same gene ^[1][2].

The Same Genetic Root and Colon Cancer Risk

Both FAP and Gardner Syndrome are caused by a germline pathogenic variant in the APC gene ^[2]. While the specific genetic variant can differ from family to family, the underlying gene involved is the same. In most cases, the mutation is inherited from a parent in an autosomal dominant pattern, meaning a carrier has a 50% chance of passing it to each child ^[2].

Because the genetic root is the same, people with Gardner Syndrome face the same colon cancer risks as those with classic FAP ^[3]. Without medical intervention, classic FAP causes hundreds to thousands of polyps in the colon and carries a nearly 100% lifetime risk of developing colorectal cancer, with diagnosis often occurring by age 35 to 40 ^[4][2]. (A milder form, attenuated FAP, has fewer polyps and a later cancer risk). The screening, surveillance, and surgical treatments for the colon generally follow the same FAP-based principles, though your care team will individualize your surgical plan based on your polyp burden, desmoid tumor risk, and other factors ^[3].

What Makes Gardner Syndrome Unique?

The term “Gardner Syndrome” is used when a person with FAP prominently displays specific extracolonic (outside the colon) physical features ^[5][1]. These features can sometimes be the first clue of the condition before colon polyps are discovered ^[6]. They include:

• Osteomas: Non-cancerous bone growths, most commonly found on the skull and jaw ^[7][8]. While usually harmless, they should be monitored by a doctor.
• Dental Abnormalities: Issues such as extra teeth (supernumerary teeth), impacted teeth that don’t emerge properly, or odontomas (harmless tumors in the gums or jaw) ^[9][6].
• Epidermoid Cysts: Common cysts under the skin ^[10][6]. They are usually benign, but a new, painful, rapidly growing, or infected-looking cyst should be examined by a doctor.
• Desmoid Tumors: Fibrous tumors that develop in the body’s connective soft tissue, often in the abdomen ^[11][8]. While they are “non-cancerous” (meaning they do not spread to other organs), they can be locally aggressive. This means they can grow into nearby tissues, compress organs, or cause bowel blockages, making them potentially serious ^[11].

Other Important Health Screenings

Whether your condition is called Gardner Syndrome or FAP, the underlying APC mutation means you need surveillance for other potential issues. The absence of skin or bone features does not remove the need for standard FAP monitoring ^[6]. People on the FAP spectrum also have a risk for upper-gastrointestinal polyps (especially in the duodenum) and papillary thyroid carcinoma ^[11]. Regular upper endoscopies and thyroid screenings are an important part of your ongoing care ^[11].

Why the Different Names?

Decades ago, doctors categorized patients based strictly on their physical symptoms ^[1]. Someone who primarily had colon polyps was diagnosed with FAP, while someone who also had prominent bone growths and skin cysts was diagnosed with Gardner Syndrome ^[1][10]. As genetic testing advanced, doctors discovered that both conditions share mutations in the APC gene, so they are now viewed as a spectrum rather than separate diseases ^[1][10].

You may hear your doctors use the terms interchangeably, but “FAP” is the broader and more accurate clinical diagnosis today. Learning about a near-certain untreated cancer risk and an inherited family condition can be frightening, but planned surveillance and risk-reducing treatments are highly effective ways clinicians manage FAP.