An Ominous Case of Diarrhea: Familial Adenomatous Polyposis

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Purpose: Familial Adenomatous Polyposis (FAP) is an autosomal dominant disease which is caused by a germline mutation in the adenomatous polyposis coli gene (APC) which is located on chromosome 5. It is the most common form of hereditary polyposis syndromes. With an incidence of 1/10000 to 1/30000 live births, FAP diagnosis is based upon the presence of more than 100 adenomatous colorectal polyps. Suggestive symptoms include rectal bleeding, abdominal pain, weight loss and less commonly diarrhea. Case Report: A 24 year old African-American male with no past medical history presented with watery non-bloody diarrhea for two weeks. His family history was significant for colon polyps in his mother (at age 56) and colon cancer in his maternal grandmother (at the age 60). On physical exam, patient was well kempt, moderately built, pale with no skin changes; furthermore, his abdominal examination was unyielding except for a digital rectal examination that was remarkable for guaiac positive stools. Laboratory work-up revealed, hemoglobin of 5.6, MCV of 54 and RDW of 22.4, platelets of 519 along with a peripheral smear showing microcytosis and hypochromia. The iron profile was consistent with severe iron deficiency anemia. The rest of the laboratory values- including ESR, CRP, Chemistry and liver profiles- were within normal limits. His stool studies were completely normal. Subsequently, patient underwent colonoscopy which depicted a large number of polyps scattered throughout the colon. Pathology confirmed the diagnosis of adenomatous polyposis. Patient had an upper endoscopy that showed few fundic polyps and a prominent duodenal papilla. Patient was referred for surgical evaluation for total colectomy. He was advised about the need for regular follow up and endoscopic surveillance; genetic and family counseling were also recommended. Discussion: FAP is an inherited colorectal cancer syndrome and accounts for 1 percent of all cases of colorectal cancer. Patients with FAP develop hundreds to thousands of colon polyps, usually starting in the teens. All patients will develop colorectal cancer by age 40 if left untreated. Extracolonic malignancies are fairly common in FAP with duodenal cancer being the second leading cause of cancer deaths in patients with FAP, once the colon has been removed. Symptoms are quite subtle at times and can be easily missed, especially that the patient population affected by the disease is young and commonly adamant about seeking adequate medical care. Herein, our case highlights that, serious medical disease could present with a subtle and often overlooked symptom like diarrhea.