Peutz-Jeghers' syndrome is a rare hereditary disease inherited by an autosomal dominant type, manifested by a characteristic clinical picture of skin lesions and hamartomas of the gastrointestinal tract. Complications of the disease include bleeding from polyps, anemia, intussusception and intestinal necrosis, as well as a high likelihood of developing malignant tumors. For the first time the syndrome was described at the beginning of the last century, and it is of interest to dermatologists, gastroenterologists, oncologists and surgeons due to the clinical heterogeneity of intestinal and skin manifestations. The article describes a clinical case of a 5-year-old girl with the Peutz-Jaegers syndrome. The patient complained of periodic dull abdominal pain that worsened after eating solid food. During the examination of the skin and mucous membranes the doctors discovered rashes on the face: perioral area, on the red border of the lips and on the mucous membrane of the lips, inside the cheeks, hard palate. Esophagogastroduodenoscopy (EGDS) revealed a polyp on a pedicle in the prepyloric part - it was removed during repeated EGDS under endotracheal anesthesia. Fibrocolonoscopy revealed hyperpigmentation of the dome of the cecum. To confirm the diagnosis, the doctors carried out DNA testing which found a mutation of the STK11 gene. Pigmentation of the perioral area is an early symptom of Peutz-Jeghers' syndrome suggesting optimal examination. Early recognition of the syndrome in children is important in the context of reducing the risk of developing intestinal obstruction, bleeding, and cancer complications in the future. © 2021 National Academy of Pediatric Science and Innovation. All rights reserved.