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Peutz-Jeghers syndrome is a rare, autosomal dominant polyposis syndrome. Presenting with a remarkable phenotype including development of characteristic gastrointestinal polyps, mucocutaneous pigmentations, and an increased risk of cancer, the syndrome has been subject to many studies concerning the natural course of disease. In most patients, pathogenic germline variants are detected in the STK11 gene including cases of mosaicism and structural variants. Yet, studies assessing the effect of surveillance, understanding of cancer development, as well as clinical studies evaluating chemoprevention are lacking. In addition, the impact of Peutz-Jeghers syndrome on mental health, education, and family planning are insufficiently addressed. In this progress report, we describe current knowledge, clinical phenotype, surveillance strategies, and future areas of research., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Peutz-Jeghers syndrome (PJS) is an autosomal dominant hereditary polyposis syndrome causing increased morbidity and mortality due to complications of polyposis and the development of cancer. STK11 is the only gene known to be associated with PJS, although in 10%-15% of patients fulfilling the diagnostic criteria no pathogenic variant (PV) is identified. The primary aim of this study was to identify the genetic etiology in all known PJS patients in Denmark and to estimate the risk of cancer, effect of surveillance and overall survival. We identified 56 patients (2-83 years old) with PJS. The detection rate of PVs was 96%, including three cases of mosaicism (6%). In two patients a variant was not detected. At the age of 40 years, the probabilities of cancer and death were 21% and 16%, respectively; at the age of 70 years these probabilities were 71% and 69%. Most cases of cancer (92%) were identified between the scheduled examinations in the surveillance program. These observations emphasize that PJS should be regarded as a general cancer predisposition syndrome, where improvement of clinical care is needed., (© 2023 The Authors. Clinical Genetics published by John Wiley & Sons Ltd.)

Background: Guidelines from the European Hereditary Tumor Group as well as The Danish National Guidelines for Peutz-Jeghers Syndrome (PJS) state that both prenatal diagnosis and preimplantation genetic testing for monogenic disorders (PGT-M) should be offered to patients with PJS. However, only a few cases resulting in viable pregnancies have been published., Objective: We present two cases of PJS patients going through PGT-M for PJS. We highlight the awareness of this possibility and discuss the technical and ethical challenges of performing PGT-M for PJS., Methods and Results: Case 1: A 36-year-old male with PJS and his partner were referred for genetic counseling. The patient carried a pathogenic de novo variant in STK11 . After a terminated pregnancy of a fetus carrying the same pathogenic variant, microsatellite polymorphic marker analysis was established, and the patient was offered PGT-M. The female partner of the patient gave birth to a healthy boy after five years of fertility treatment. Case 2: A 35-year-old female with PJS and her partner were referred for genetic counseling. She carried an inherited pathogenic STK11 variant. The couple was offered PGT-M. Genetic testing of the embryos was performed using microsatellite polymorphic markers. After two rounds of oocyte extraction a blastocyst predicted not to be affected by PJS was identified. The blastocyst was transferred; however, this did not result in a viable pregnancy., Conclusions: PGT-M can be offered to patients with PJS. The process may be long and filled with ethical dilemmas requiring patients to be motivated and persistent.

Peutz-Jeghers syndrome (PJS) is a hereditary polyposis syndrome characterized by hamartomatous Peutz-Jeghers polyps in the gastrointestinal tract, mucocutaneous pigmentations, and increased risk for intestinal and extraintestinal cancer. In more than two-third of patients it is possible to detect pathogenic variants in the serine/threonine kinase 11 (STK11) gene, but so far is knowledge about genetic causes in the remaining part of patients limited. Reports of STK11 mosaicism are rare but may be an explanation in some patients without initial findings of pathogenic variants in STK11. We report two Danish patients with STK11 mosaicism detected in blood when using Next-Generation Sequencing. This is only the sixth and seventh patient reported in the literature, and we compare phenotypes of the reported cases. The results indicate that STK11 mosaicism is more frequent than anticipated and highlight that mosaicism should be considered in patients with clinical suspicion of PJS or patients fulfilling the diagnostic criteria.

Hereditary polyposis syndromes are characterized by a large number and/or histopathologically specific polyps in the gastrointestinal tract and a high risk of both colorectal cancer and extracolonic cancer at an early age. While the genes responsible for some of the syndromes, eg, APC in familial adenomatous polyposis and STK11 in Peutz-Jeghers syndrome, have been known for decades, novel genetic causes have recently been detected that have shed light on the broader clinical spectrum of syndromes. Genetic diagnoses are important because they can facilitate a personalized surveillance program. Furthermore, at-risk members of the patient's family can be tested and enrolled in surveillance as needed. In some cases, prenatal diagnostics should be offered. In this paper, we describe the development in germline genetics of the hereditary polyposis syndromes over the last 10– 12 years, their clinical characteristics, as well as how to implement genetic analyses in the diagnostic pipeline. [ABSTRACT FROM AUTHOR]