Familial adenomatous polyposis: Case report in two sisters at a university hospital in Rio de Janeiro

Familial Adenomatous Polyposis (FAP) is an autosomal dominant disease caused by a mutation in the Adenomatous Polyposis Coli (APC) gene. Its main symptoms include hematochezia, altered bowel habits, and abdominal pain. Diagnosis is based on the presence of multiple colonic adenomas (typically >100 in the classic form), a suggestive family history, and genetic confirmation. Proctocolectomy is the treatment of choice for patients with extensive involvement to reduce the risk of colorectal cancer, but the timing of the procedure should be individualized. We report the case of two sisters, aged 8 and 11, presenting with epigastric pain but no bleeding. Their maternal family history was positive for FAP, with multiple cases across three generations (great-grandmother, grandmother, and mother). A hereditary colorectal cancer panel was performed, identifying a heterozygous variant in the APC gene. Colonoscopy revealed macroscopic findings of sessile colonic polyps (0-Is), and polypectomy was performed. Histopathological examination revealed tubular adenoma with low-grade dysplasia, except for one hyperplastic polyp in the transverse colon of the second sister. FAP is a familial disease with specific symptoms, and family history is crucial for diagnostic screening. Colonoscopy is mandatory, with multiple biopsies following polypectomy. Genetic testing should also be performed for diagnosis. Most patients with FAP require prophylactic colectomy to prevent progression to colorectal cancer.