Gardner’s Syndrome is a rare, inherited disorder characterized by the growth of numerous abnormal tissues affecting multiple organ systems. It is a specific subtype of Familial Adenomatous Polyposis (FAP), defined by the development of many polyps in the large intestine. Gardner’s Syndrome is distinguished by the presence of growths that occur outside of the gastrointestinal tract.
The Genetic Root Cause
The underlying cause of Gardner’s Syndrome is a mutation in the Adenomatous Polyposis Coli (\(APC\)) gene. The \(APC\) gene normally functions as a tumor suppressor, regulating cell growth and division. A mutation causes the resulting protein to be non-functional, leading to uncontrolled cellular growth and the formation of tumors and polyps.
Gardner’s Syndrome is inherited in an autosomal dominant pattern, meaning only one copy of the mutated \(APC\) gene is needed to cause the condition. A person with the syndrome has a 50% chance of passing the gene to their children. While most cases are inherited, approximately 20% arise from a spontaneous, non-inherited mutation.
Defining Features in the Colon
The most significant feature of Gardner’s Syndrome is the development of massive numbers of adenomatous polyps throughout the colon and rectum. These growths, initially benign, often appear starting around puberty or the mid-teens. The polyps can number from one hundred to many thousands, sometimes appearing dense or carpet-like during a colonoscopy.
The presence of these numerous adenomatous polyps carries a near-100% risk of progression to colorectal cancer if the condition is left untreated. Malignant transformation typically occurs by the time a person reaches their late 30s or early 40s, with the average age for cancer detection being around 39 years. This high risk necessitates aggressive, proactive management of the syndrome.
Manifestations Outside the Colon
The features distinguishing Gardner’s Syndrome are the specific growths occurring outside the colon. These extra-colonic manifestations include osteomas, which are benign bone growths often found in the skull and jaw. Osteomas can sometimes be detected before colonic polyps form, often identified via routine X-rays or by a dentist.
Soft tissue tumors are also characteristic, including epidermoid cysts and desmoid tumors. Epidermoid cysts are small, non-cancerous lumps beneath the skin, typically on the face, scalp, and extremities. Desmoid tumors are locally aggressive and can grow large enough to compress vital organs, posing a serious health risk despite being technically non-cancerous.
Other findings include dental abnormalities, such as supernumerary (extra) or impacted teeth. Many patients also present with Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE), which appears as dark, flat spots on the retina. Although CHRPE lesions are usually harmless, four or more lesions serve as a highly specific early diagnostic indicator.
Diagnosis and Long-Term Management
Diagnosis of Gardner’s Syndrome begins with a thorough clinical assessment, noting the presence of characteristic extra-colonic features like osteomas and epidermoid cysts. This is followed by endoscopic screening, such as a colonoscopy, to confirm the presence of numerous colorectal polyps. Definitive confirmation comes from genetic testing, which sequences the patient’s DNA to identify the specific mutation in the \(APC\) gene.
Long-term management focuses on cancer prevention due to the inevitable progression of colonic polyps to malignancy. The only effective treatment to eliminate the risk of colorectal cancer is a prophylactic colectomy, the surgical removal of the colon. This procedure is typically recommended when a significant number of polyps are detected, often in late adolescence or early adulthood.
Following colectomy, patients require lifelong surveillance for other potential complications. This includes regular upper gastrointestinal endoscopy to check for polyps in the stomach and small intestine, particularly the duodenum, which carry a cancer risk. Ongoing monitoring is also necessary for desmoid tumors and potential cancers in the thyroid gland, requiring a coordinated approach.