Challenges in diagnosing and interdisciplinary treatment of a patient with Gardner syndrome: a case report

Background Gardner syndrome is a phenotypic variant of familial adenomatous polyposis (FAP) with autosomal dominant inheritance, characterized by the diagnostic triad of multiple gastrointestinal polyps, skin and soft tissue tumors, and osteomas, which typically present in the mandible, skull, and long bones. Early detection of these signs is crucial due to the high risk of malignant transformation of colonic polyps before the age of 50. Case presentation: A 17-year-old male patient presented to a dental clinic seeking dental alignment. Clinical examination revealed facial asymmetry, and panoramic radiography showed multiple osteomas, supernumerary teeth, retained deciduous teeth, and impacted permanent teeth. Additionally, the patient had a history of hepatoblastoma at 18 months of age. Given the clinical suspicion of Gardner syndrome, an endoscopic evaluation was performed, revealing more than 40 polyps in the right colon and over 100 sessile polyps in the fundus and body of the stomach. Histopathological analysis reported colonic adenomas with low- and high-grade dysplasia, along with fundic gland polyps. A genetic panel confirmed a heterozygous pathogenic variant in exon 5 of the APC gene: c.509_512del (p.Asp170Valfs*4). Subsequently, first-degree relatives underwent genetic testing, which revealed that the patient’s mother and 21-year-old brother were asymptomatic carriers of the same pathogenic variant, with no extracolonic manifestations. Conclusions This case illustrates how a diagnostic suspicion originating in dental practice, combined with a multidisciplinary approach, can play a decisive role in both the diagnosis and prevention of complications associated with Gardner syndrome. It also underscores the importance of genetic testing in autosomal dominant disorders to identify asymptomatic carriers, enable early diagnosis, and implement timely prophylactic measures in at-risk relatives.