Peutz–Jeghers syndrome (often abbreviated PJS) is an autosomal dominant genetic disorder characterized by the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa (melanosis). This syndrome can be classed as one of various hereditary intestinal polyposis syndromes and one of various hamartomatous polyposis syndromes. It has an incidence of approximately 1 in 25,000 to 300,000 births. Signs and symptoms The risks associated with this syndrome include a substantial risk of cancer, especially of the breast and gastrointestinal tracts. Colorectal is the most common malignancy, with a lifetime risk of 39 percent, followed by breast cancer in females with a lifetime risk of 32 to 54 percent. Patients with the syndrome also have an increased risk of developing carcinomas of the liver, lungs, breast, ovaries, uterus, testes, and other organs. Specifically, it is associated with an increased risk of sex-cord stromal tumor with annular tubules in the ovaries. Due to the increased risk of malignancies, direct surveillance is recommended. The average age of first diagnosis is 23. The first presentation is often bowel obstruction or intussuseption from the hamartomatous gastrointestinal polyps. Dark blue, brown, and black pigmented mucocutaneous macules, are present in over 95 percent of individuals with Peutz-Jeghers syndrome. Pigmented lesions are rarely present at birth, but often appear before 5 years of age. The macules may fade during puberty. The melanocytic macules are not associated with malignant transformation. Complications associated with Peutz-Jeghers syndrome include obstruction and intussusception, which occur in up to 69 percent of patients, typically first between the ages of 6 and 18, though surveillance for them is controversial. Anemia is also common due to gastrointestinal bleeding from the polyps. Genetics In 1998, a gene was found to be associated with the mutation. On chromosome 19, the gene known as STK11 (LKB1) is a possible tumor suppressor gene. It is inherited in an autosomal dominant pattern, which means that anyone who has PJS has a 50% chance of passing the disease on to their offspring. Peutz–Jeghers syndrome is rare and studies typically include only a small number of patients. Even in those few studies that do contain a large number of patients, the quality of the evidence is limited due to pooling patients from many centers, selection bias (only patients with health problems coming from treatment are included), and historical bias (the patients reported are from a time