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We report the case of a female found to have mosaicism for mutation in the STK11 gene, with the mutant allele expressed in her gametes, evident by her affected offspring, and in her gastrointestinal tract demonstrated on an excised polyp analysed for diagnosis. Mosaicism for Peutz-Jeghers syndrome (PJS) has been reported in a small number of cases previously but a clinical presentation such as this has not previously been described. This finding of mosaicism was several years after initial investigations failed to identify the same STK11 mutation in this woman whose son was diagnosed with PJS at a young age. This case highlights the importance of considering mosaicism as an explanation for apparent de novo cases of PJS syndrome. It also has implications for genetic counselling, predictive testing and cancer screening.

The genetic predisposition Peutz-Jeghers Syndrome (PJS) has been shown to be associated with mutations in the serine threonine kinase 11 (STK11) gene but only a proportion of probands have been shown to harbour changes in the gene. The remaining patients were proposed to be either associated with a second PJS gene or they harboured more cryptic mutations within the STK11 gene itself. With the introduction of the multiplex ligation probe amplification (MLPA) assay, large sequence losses or gains can be more readily identified. In this report we have screened 33 PJS patients from unrelated families, employing a combination of denaturing high-performance liquid chromatography, direct DNA sequencing and the MLPA assay to identify deleterious changes in the STK11 gene. The results revealed that 24 (73%) of patients diagnosed with PJS-harboured pathogenic mutations in the STK11 gene, including 10 (36%) with exonic or whole-gene deletions. No phenotypic differences were identified in patients harbouring large deletions in the STK11 gene compared to patients harbouring missense or nonsense mutations. Mutation analysis in PJS should include techniques such as MLPA to identify large exonic or whole-gene deletions and rearrangements. The high proportion of families with identifiable mutations in the STK11 gene using this range of techniques suggests that most, if not all PJS, is attributable to mutations in the STK11 gene, perhaps including as yet undiscovered changes in promoter or enhancer sequences or other cryptic changes.

Background: Although an increased cancer risk in Peutz-Jeghers syndrome is established, data on the spectrum of tumors associated with the disease and the influence of germ-line STK11/LKB1 (serine/threonine kinase) mutation status are limited., Experimental Design: We analyzed the incidence of cancer in 419 individuals with Peutz-Jeghers syndrome, and 297 had documented STK11/LKB1 mutations., Results: Ninety-six cancers were found among individuals with Peutz-Jeghers syndrome. The risk for developing cancer at ages 20, 30, 40, 50, 60, and 70 years was 2%, 5%, 17%, 31%, 60%, and 85%, respectively. The most common cancers represented in this analysis were gastrointestinal in origin, gastroesophageal, small bowel, colorectal, and pancreatic, and the risk for these cancers at ages 30, 40, 50, and 60 years was 1%, 9%, 15%, and 33%, respectively. In women with Peutz-Jeghers syndrome, the risk of breast cancer was substantially increased, being 8% and 31% at ages 40 and 60 years, respectively. Kaplan-Meier analysis showed that cancer risks were similar in Peutz-Jeghers syndrome patients with identified STK11/LKB1 mutations and those with no detectable mutation (log-rank test of difference chi2 = 0.62; 1 df; P = 0.43). Furthermore, the type or site of STK11/LKB1 mutation did not significantly influence cancer risk., Conclusions: The results from our study provide quantitative information on the spectrum of cancers and risks of specific cancer types associated with Peutz-Jeghers syndrome.

Peutz-Jeghers syndrome (PJS) is a rare cancer predisposition, which is characterized by the presence of hamartomatous polyposis and mucocutaneous pigmentation. A significant proportion of both familial and sporadic forms of this disorder are associated with mutations in the STK11 (serine/threonine kinase 11)/LKB1 gene. In this report we present a series of Australian PJS cases, which suggest that mutations in the STK11 gene do not account for many families or patients without a family history. The most likely explanation is either the presence of another susceptibility gene or genetic mosaicism in the non-familial patients.

Peutz-Jeghers syndrome is a rare genetic disorder characterized by mucocutaneous melanin deposition, intestinal polyposis and an increased risk of cancer, both intestinal and extra-intestinal. We describe the current status of diagnosis and the methods by which the consequences of this condition can be minimized. A surveillance program for those diagnosed is also included.

The classical pigmentation of Peutz-Jeghers syndrome distinguishes it immediately from the other polyposis syndromes. Less widely appreciated than this most obvious manifestation are the pitfalls in management presented by the risk of cancer and by the performance of multiple laparotomies that also characterize this condition. An outline of these risks and an approach that minimizes them is presented.

Relaparotomy occurs commonly in patients with the Peutz-Jeghers syndrome, and at quite short intervals. Between 1943 and 1987 laparotomies were performed on 54 occasions in 23 patients with the Peutz-Jeghers syndrome who at some time came under the care of St. Mark's Hospital. In four patients repeat laparotomy was performed within a single year. Between 1987 and 1989 a further five patients have undergone laparotomy with on-table small bowel endoscopy. External palpation and small bowel transillumination failed to demonstrate 17 out of a total of 45 hamartomas (38 per cent). Of these 17 polyps identified endoscopically, 11 (65 per cent) were sufficiently large that a snare was used to remove them. We recommend peroperative enteroscopy as an adjunct to surgery in the Peutz-Jeghers syndrome.

Among 72 patients with the Peutz-Jeghers syndrome malignant tumours have developed in 16 (22%) of whom all but one have died. There were nine gastrointestinal and seven nongastrointestinal tumours. The relative risks of death from gastrointestinal cancer and all cancers were 13 (95% CI 2.7-38.1) and 9 (95% CI 4.2-17.3) respectively. The chance of dying of cancer by the age of 57 was 48%. There is evidence for a hamartoma/carcinoma sequence in the Peutz-Jeghers syndrome, suggesting that the gene locus involved is relevant to the development of malignancy in general.