SHM Converge Scientific Abstract ePoster Gallery-Taking the 'Family' Out of Familial Adenomatous Polyposis: A Case of De Novo Polyposis

Pdf Summary

This case highlights a 28-year-old woman with no significant medical or family history who presented with hematochezia, abdominal cramps, and major weight loss. She was found to have severe iron-deficiency anemia, an elevated CEA, and a palpable abdominal/chest wall mass. Colonoscopy showed two fungating rectal masses with innumerable adenomas throughout the colon, and upper endoscopy revealed extensive gastric and duodenal polyps. Biopsies confirmed colorectal adenocarcinoma, staged by MRI as T4aN2b. A chest wall lesion was also biopsied and diagnosed as desmoid fibromatosis, further supporting classic familial adenomatous polyposis (FAP).<br /><br />The report emphasizes that FAP is an autosomal dominant syndrome caused most often by APC mutations and that 20–30% of cases may arise de novo, meaning a negative family history does not rule it out. FAP is rare but carries near-universal colorectal cancer risk without treatment and can include extracolonic features such as desmoid tumors and thyroid cancer. Because diagnosis is often delayed in de novo or mosaic cases, clinicians should consider FAP in young patients with red-flag features such as bleeding, iron deficiency, weight loss, multiple adenomas, or desmoid disease.<br /><br />The authors note that current guidelines recommend multigene panel testing for patients with more than 10–20 cumulative adenomas. If a pathogenic variant is identified, cascade testing for relatives is important, as early surveillance can substantially improve survival and reduce cancer burden. Definitive treatment typically requires colectomy and lifelong surveillance.

Asset Subtitle

Pedro Ramos

Meta Tag

Author List Joyce Ji, Lana Bridi, Pedro Ramos

Category Clinical Vignettes

Concept Familial Adenomatous Polyposis

Concept Colonoscopy

Concept Colectomy

Concept De Novo Mutation

Concept Hematochezia

Distinguished Non-Finalist

Presenter Organization UC San Diego Health Center

Presenting Author Pedro Ramos

Track Adult

Keywords

familial adenomatous polyposis

APC mutation

colorectal adenocarcinoma

desmoid fibromatosis

multiple adenomas

iron-deficiency anemia

rectal mass

gastric polyps

duodenal polyps

multigene panel testing

Familial Adenomatous Polyposis

Colonoscopy

Colectomy

De Novo Mutation

Hematochezia