STK11 and Peutz-Jeghers syndrome: Peutz-Jeghers syndrome (PJS) is a rare autosomal dominant inherited disorder, caused by a constitutional pathogenic variant (PV) in the tumour suppressor gene STK11 (also known as LKB1) [1, 2] and clinically characterized by the development of Peutz-Jegher type hamartomatous polyps in the gastrointestinal tract, mucocutaneous pigmentation [3–5] The estimated prevalence of PJS is most consistently reported to be somewhere between 1 in 50,000 to 1 in 200,000, with a wider range of estimates from some studies [5–7].