28th February 2025

A 32-year-old man presents to the emergency department with his older sister with a 3-day history of colicky abdominal pain

A 32-year-old man presents to the emergency department with his older sister with a 3-day history of colicky abdominal pain, nausea and vomiting. One week ago, he was passing black tarry stool, but did not seek any medical attention as he was taking care of their mum who has just been diagnosed with bowel cancer. He is not sure if he is still passing the black stool as his last bowel movement was 3 days ago.

On examination, temperature is 37.8°C, BP 100/70 mmHg and heart rate 110 bpm. There is marked generalised abdominal tenderness with guarding, and some hyperpigmented lesions on the palms, which the patient states have been present since childhood. He also mentions that his mum and paternal uncle have similar lesions.

Abdominal X-ray shows small bowel obstruction and he undergoes emergency laparotomy. A jejunoileal intussusception and multiple polyps around the ligament of Treitz are identified during the surgery. He has segmental bowel resection and is stepped down to the ward where he is commenced on intravenous broad-spectrum antibiotics and analgesia.

What gene is associated with the most likely underlying condition?

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