Polyps and inherited gastrointestinal cancer syndromes: SAQ

This boy cannot be dismissed as having benign isolated juvenile polyps. Four juvenile polyps combined with a strong family history of polyposis and early pancreatic cancer redefine the picture as a juvenile polyposis syndrome until proven otherwise, and his mother's colectomy for hundreds of polyps raises familial adenomatous polyposis as a parallel concern. The questions turn on the diagnostic criteria, the genes and cancer risks, and the surveillance and genetic plan for the child and the family. [1]

Question 1 (10 marks)

Explain how you would classify this child's polyps, the criteria that separate an isolated juvenile polyp from a syndrome, and which inherited syndromes you would consider in this family. [1]

The decisive first step is histology and polyp count. An isolated juvenile polyp is a benign hamartomatous overgrowth removed once at colonoscopy, but juvenile polyposis syndrome is defined by more than five juvenile polyps in the colorectum, any juvenile polyp elsewhere in the gastrointestinal tract, or any number of juvenile polyps with a family history. This boy has four colonic juvenile polyps and a clear family history, so he meets the syndromic definition, and the history should prompt germline testing rather than reassurance. The juvenile polyp histology with this family pattern points toward juvenile polyposis syndrome caused by SMAD4 or BMPR1A. The mother's colectomy for hundreds of polyps, however, raises familial adenomatous polyposis from an APC mutation, and the aunt's early pancreatic cancer is a recognised extraintestinal malignancy of Peutz-Jeghers and several familial cancer syndromes, so the full differential includes juvenile polyposis, familial adenomatous polyposis, Peutz-Jeghers syndrome, and MUTYH-associated polyposis, distinguished by polyp histology and germline testing rather than by the bleeding alone. [1]

Question 2 (10 marks)

Outline the cancer risks of the inherited polyposis syndromes and your surveillance and genetic-testing plan for this child and his family. [2]

The cancer risks are syndrome-specific and drive the surveillance. Juvenile polyposis carries a cumulative colorectal cancer risk of roughly thirty-eight to thirty-nine per cent and a meaningful gastric cancer risk. Classic familial adenomatous polyposis produces hundreds to thousands of adenomas and, untreated, colorectal cancer at a median age in the late thirties to early forties, with desmoid tumours as a leading cause of death. Peutz-Jeghers carries the highest overall burden, with a lifetime cancer risk that may exceed eighty per cent across gastrointestinal, breast, pancreatic, gynaecological, and testicular sites. My plan is to refer the family to a familial cancer service for germline testing, beginning with testing of the affected mother to identify the pathogenic variant, followed by predictive testing of the boy once the family mutation is known and with appropriate counselling. Surveillance follows the ESPGHAN framework: for juvenile polyposis, oesophagogastroduodenoscopy and colonoscopy beginning at the onset of symptoms or the early to mid-teens and repeated every one to three years with polypectomy; for familial adenomatous polyposis, flexible sigmoidoscopy from the early to mid-teens moving to colonoscopy once adenomas appear, with prophylactic colectomy in the late teens to mid-twenties once the polyp burden is not endoscopically controllable. I would also offer predictive testing and age-appropriate surveillance to his siblings and other at-risk relatives, and plan a structured transition to adult familial cancer care as he approaches adolescence. [3]