21st July 2023

A 29-year-old man is referred to gastroenterology after presenting to his GP with a 3-month history of lower abdominal pain

A 29-year-old man is referred to gastroenterology after presenting to his GP with a 3-month history of lower abdominal pain with intermittent PR bleeding. He has no past medical history, takes no regular medications and has been entirely well prior to the onset of these symptoms. His father had colorectal cancer aged 40, managed with surgical resection. The man undergoes an urgent colonoscopy which shows an ulcerated lesion in the proximal colon. Biopsies confirm locally invasive colorectal cancer. In light of his age and family history, he subsequently undergoes molecular genetic testing, which reveals a gene mutation consistent with a diagnosis of Lynch syndrome.

Which gene mutation is most likely to have been identified in this patient?

Select the SINGLE most appropriate option from the list below. Select ONE option only.