Peutz-Jeghers syndrome (PJS) is an autosomal dominant disorder, caused by germline variants in the serine/threonine kinase 11 (STK11) gene. However, mosaic variants in STK11 gene have been rarely described. A 25-year-old woman diagnosed with PJS due to multiple hamartomatous polyps in the gastrointestinal tract was referred to our clinic. In the molecular diagnosis, the patient was evaluated using the STK11 gene sequence analysis and multiplex ligation-dependent probe amplification (MLPA) method, which suggested no pathogenic variant to account for the clinical picture. Given that the clinical findings of the patient were consistent with those of PJS, the raw data from next-generation sequencing (NGS) were re-examined for mosaicism which led to the detection of a novel mosaic c.920 + 1G > T variant in STK11 gene with a rate of 23% (1860x). Deep read-level NGS was performed on buccal mucosa and polyp samples to determine mosaicism levels in other tissues. Variant frequencies were 29% (710x) and 31% (1301x), respectively. Mosaicism should be considered in cases with clear clinical diagnostic criteria, such as PJS, where the pathogenic variant cannot be detected by sequence analysis and MLPA methods. Identification of mosaicism in these patients is very important as it can have an impact on patient follow-up and genetic counseling for relatives.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare hereditary syndrome characterized by the growth of hamartomatous polyps in the gastrointestinal tract, perioral pigmentation and an increased risk of malignant neoplasms. The syndrome is caused by a pathogenic variant in the STK11 gene.
OBJECTIVE: To assess the clinical picture and treatment of Russian patients with PJS.
METHODS: A retrospective analysis of 30 patients from 25 families with an established diagnosis of PJS who were in the Ryzikh State Scientific Center for Coloproctology from 2011 to 2021 was carried out. All patients underwent instrumental examination, including esophagogastroduodenoscopy, colonoscopy, X-ray examination of the small intestine/CT-enterography, in the absence of invaginates - video capsule endoscopy, as well as molecular genetic examination for the presence of pathogenic variants in the STK11 gene. All removed polyps were subjected to the histological examination.
RESULTS: The analysis of the clinical picture allowed us to establish the following data: the first complaints in patients were noted in childhood and adolescence, while the median age was 11 [7; 19] (0.5-24) years; pathogenic variants in the STK11 gene were identified in 26 (87%) cases, among which 10 were described for the first time; during the initial examination, polyps in the small intestine were detected in all 30 (100%) patients, in the stomach - in 23/30 (77%) patients, and in the colon - in 21/30 (70%); with an age, an increase in the number of polyps in all parts of the gastrointestinal tract was noted; before the diagnosis operations were performed urgently for intestinal obstruction; after the diagnosis of PJS, when polyps were detected in the gastrointestinal tract, endoscopic polypectomies were performed; if endoscopic removal of hamartomatous polyps was impossible, patients were operated as planned; malignant diseases of the predominantly reproductive system were detected in 8/30 (27%) patients. The median age of cancer detection was 52 [31; 52] (17-59) years.
CONCLUSIONS: Russian patients with PJS have population-specific features in the clinical picture of the course of the disease, which dictates the need to develop their own recommendations for monitoring and treatment of such patients.
Обоснование. Синдром Пейтца–Егерса (СПЕ) – редкий наследственный синдром, характеризующийся ростом гамартомных полипов в желудочно-кишечном тракте, периоральной пигментацией и повышенным риском развития злокачественных новообразований. Синдром обусловлен патогенным вариантом в гене STK11. Цель. Оценить клиническую картину и лечение российских пациентов с СПЕ. Материалы и методы. Проведен ретроспективный анализ 30 пациентов из 25 семей с установленным диагнозом СПЕ, наблюдавшихся в ФГБУ «ГНЦК им. А.Н. Рыжих» с 2011 по 2021 г. Всем пациентам проводилось инструментальное исследование, включающее эзофагогастродуоденоскопию, колоноскопию, рентгенологическое исследование тонкой кишки/КТ-энтерографию, при отсутствии инвагинатов – видеокапсульную эндоскопию, а также ДНК-диагностику гена STK11. Все удаленные полипы подвергались гистологическому исследованию. Результаты. Анализ клинической картины позволил установить следующие данные: первые жалобы у пациентов отмечались в детско-юношеском возрасте, при этом медиана возраста составила 11 [7; 19] (0,5–24) лет; патогенные варианты в гене STK11 выявлены в 26 (87%) наблюдениях, среди которых 10 описаны впервые; при первичном обследовании у всех 30 (100%) пациентов выявлялись полипы в тонкой кишке, в желудке – у 23/30 (77%) пациентов, в толстой кишке – у 21/30 (70%); с возрастом отмечалось увеличение количества полипов во всех отделах желудочно-кишечного тракта; до постановки диагноза операции выполнялись в экстренном порядке по поводу кишечной непроходимости, после постановки диагноза СПЕ при выявлении полипов в желудочно-кишечном тракте выполнялись эндоскопические полипэктомии; при невозможности эндоскопического удаления гамартомных полипов пациенты оперировались в плановом порядке; у 8/30 (27%) пациентов выявлены злокачественные заболевания. Медиана возраста выявления рака составила 52 [31; 52] (17–59) года. Заключение. У российских пациентов с СПЕ имеются популяционные особенности в клинической картине течения заболевания, что диктует необходимость разработки собственных рекомендаций по мониторингу и лечению такого рода больных.

BACKGROUND: Peutz-Jeghers syndrome (PJS) is a rare disease characterized by the presence of hamartomatous polyposis throughout the gastrointestinal tract, except for the esophagus, along with characteristic mucocutaneous pigmentation. It is caused by germline pathogenic variants of the STK11 gene, which exhibit an autosomal dominant mode of inheritance. Some patients with PJS develop gastrointestinal lesions in childhood and require continuous medical care until adulthood and sometimes have serious complications that significantly reduce their quality of life. Hamartomatous polyps in the small bowel may cause bleeding, intestinal obstruction, and intussusception. Novel diagnostic and therapeutic endoscopic procedures such as small-bowel capsule endoscopy and balloon-assisted enteroscopy have been developed in recent years.
CONCLUSIONS: Under these circumstances, there is growing concern about the management of PJS in Japan, and there are no practice guidelines available. To address this situation, the guideline committee was organized by the Research Group on Rare and Intractable Diseases granted by the Ministry of Health, Labour and Welfare with specialists from multiple academic societies. The present clinical guidelines explain the principles in the diagnosis and management of PJS together with four clinical questions and corresponding recommendations based on a careful review of the evidence and involved incorporating the concept of the Grading of Recommendations Assessment, Development and Evaluation system.
CONCLUSIONS: Herein, we present the English version of the clinical practice guidelines of PJS to promote seamless implementation of accurate diagnosis and appropriate management of pediatric, adolescent, and adult patients with PJS.

Hereditary polyposis syndrome can be divided into three categories: Ade-nomatous, serrated, and hamartomatous polyps. Hamartomatous polyps, malformations of normal tissue presenting in a disorganized manner, are characterized by an autosomal dominant inheritance pattern. These syndromes exhibit hamartomatous gastrointestinal polyps in conjunction to extra-intestinal manifestations, which require conscientious and diligent monitoring. Peutz-Jeghers syndrome, Cowden syndrome, and juvenile polyposis syndrome are the most common displays of hamartomatous polyposis syndrome (HPS). Diagnosis can be pursued with molecular testing and endoscopic sampling. Early identification of these autosomal dominant pathologies allows to optimize malignancy sur-veillance, which helps reduce morbidity and mortality in both the affected patient population as well as at-risk family members. Endoscopic surveillance is an important pillar of prognosis and monitoring, with many patients eventually requiring surgical intervention. In this review, we discuss the diagnosis, surveillance, and management of HPS.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant mutation of the STK11/LKB1 gene on chromosome 19 often characterized by mucocutaneous pigmentation, hamartomatous polyps, anemia, gastrointestinal bleeding and intussusception. We present the case of a 21-year-old female with no pertinent family history who received the diagnosis of PJS after presenting to the hospital with two episodes intussusception. Patients with PJS have an increased lifetime risk of developing stomach, small bowel, colon, pancreatic, breast, cervical, uterus and testicular cancer requiring religious surveillance at an early age.

MUTYH-associated polyposis (MAP) is an autosomal recessive disorder characterized by the development of multiple adenomatous colonic polyps and an increased lifetime risk of colorectal cancer. Germline biallelic pathogenic variants in MUTYH are responsible for MAP. The MUTYH c.934-2A>G (NM_001128425.1) variant, which is also known as c.850-2A>G for NM_001048174.2, has been identified in our laboratory in more than 800 patients, including homozygous and compound heterozygote carriers. The variant was initially classified as a variant of uncertain significance (VUS) due to lack of a MAP phenotype in biallelic carriers. In two unrelated female patients who were heterozygous carriers of this variant, further testing by RNA sequencing identified an aberrant transcript with a deletion of 9 nucleotides at the start of exon 11 (MUTYH r.934_942del9). This event is predicted to lead to an in-frame loss of 3 amino acids in a non-critical domain of the protein. This was the only splice defect identified in these patients which was not present in the controls and the aberrant transcript is derived exclusively from the variant allele, strongly supporting the cause of this splice defect as being the intronic variant, MUTYH c.934-2A>G. The splicing analysis demonstrating a small in-frame skipping of 3 amino acids in a non-critical domain along with the absence of a MAP phenotype in our internal cohort of biallelic carriers provides evidence that the variant is likely benign and not of clinical significance.

Enteroscopy resection of small bowel polyps in Peutz-Jeghers syndrome has only been described in small case series. Herein, we aimed to assess the efficacy of enteroscopy resection of small bowel polyps within a specialised tertiary care centre and the impact on intraoperative enteroscopy.
This was an observational single-centre study. All adult Peutz-Jeghers syndrome patients followed in the Predisposition Digestive Ile-de-France network who underwent an endoscopic resection of at least one small bowel polyp ≥ 1 cm by enteroscopy between 2002-2015 were included. Small bowel polyps were detected under a dedicated screening programme by previous capsule endoscopy and/or magnetic resonance enterography, performed every 2-3 years. Complete treatment was defined as the absence of polyps ≥ 1 cm after conventional endoscopic resection. Intraoperative enteroscopy or surgical resection were indicated in incomplete treatments. The overall complete treatment rate including conventional enteroscopy and intraoperative enteroscopy was also considered.
Endoscopic resection of 216 small bowel polyps (median: 8.6 per patient, size: 6-60 mm) was performed by 50 enteroscopies in 25 patients (mean age: 36 years, range: 18-71, 56% male) with small bowel polyp ≥ 1 cm. Twenty-three patients (92%) underwent 42 screening capsule endoscopies and 14 (57%) had 23 magnetic resonance enterographies during a median follow-up of 60 months. Complete treatment was achieved in 76%. Intraoperative enteroscopy and surgical resection were performed in four (16%) and two (8%) patients. Intraoperative enteroscopy improved by 16% the complete treatment rate and the overall rate was 92%. The complication rate was 6%.
This long-term study confirmed the efficacy and safety of endoscopic resection of small bowel polyps in Peutz-Jeghers syndrome. Intraoperative enteroscopy can be a complementary approach in selected cases.

Colorectal carcinoma (CRC) is the third most common cancer in men and the second most common cancer in women across the world. Most CRCs occur sporadically, but in 15-35% of cases, hereditary factors are important. Some patients with an inherited predisposition to CRC will be diagnosed with a \"genetic polyposis syndrome\" such as familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), polymerase proofreading associated polyposis (PPAP), NTHL1-associated polyposis, MSH3-associated polyposis or a hamartomatous polyposis syndrome. Individuals with ≥10 colorectal polyps have traditionally been referred for genetic diagnostic testing to identify APC and MUTYH mutations which cause FAP and MAP respectively. Mutations are found in most patients with >100 adenomas but in only a minority of those with 10-100 adenomas. The reasons that diagnostic laboratories are not identifying pathogenic variants include mutations occurring outside of the open reading frames of genes, individuals exhibiting generalized mosaicism and the involvement of additional genes. It is important to identify patients with an inherited polyposis syndrome, and to define the mutations causing their polyposis, so that the individuals and their relatives can be managed appropriately.

Even in well-described genetic syndromes, such as neurofibromatosis type 1, expansion of the phenotype should be considered as a possible explanation for atypical presentations. However, it is critical to complete the evaluation for a potential dual diagnosis, as there could be significant prognostic and management implications.

Peutz-Jeghers syndrome is an autosomal dominant inherited medical condition characterized by hyperpigmented mucocutaneous macules, hamartomatous polyps in the digestive tract, and with a greater risk of gastrointestinal and non-gastrointestinal cancers. In fact, without appropriate medical surveillance, the lifetime risk for all cancers combined may be as high as 93%. The syndrome is rare, with estimates of incidence varying between 1 in 8,300 and 1 in 280,000 live births. Infrequently, individuals present for the first time with bowel obstruction secondary to intussusception. Here, we present an interesting case of a young Burmese man who, early on, showed traits of Peutz-Jeghers syndrome, including the characteristic hyperpigmented areas on the fingers and lips. Unfortunately, the diagnosis was not made until he later developed bowel obstruction caused by an intussusception, requiring exploratory laparoscopic bowel resection. A high index of suspicion is needed to diagnose accurately. However, early identification and close surveillance can lead to excellent prognosis in these individuals.