Peutz-Jeghers syndrome is a rare autosomal dominant disorder. Approximately 1:25,000 to 1:280,000 cases are registered annually. The pathogenesis of the disease is based on the mutation of the STK 11 gene on chromosome 19. Peutz-Jeghers syndrome is characterized by several symptoms: the formation of multiple hamartomatous polyps primarily in the gastrointestinal tract and hyperpigmentation of the mucous membranes and skin. Patients with Peutz-Jeghers syndrome often develop various malignant neoplasms, mainly localized in the pancreas and colon. We describe Peutz-Jeghers syndrome in a girl 4 years 7 months old. Initially, the child was diagnosed with vitiligo due to complaints of depigmentation of the skin of the face and hands. During re-examination after half a year, foci of hyperpigmentation on the lip and mucous membranes of the oral cavity were noted. Esophagogastroduodenoscopy showed the presence of a polypous lump in the stomach. Genetic consultation confirmed the diagnosis of Peutz-Jeghers syndrome. The absence of family history indicates a sporadic case characterized by diseases with an autosomal-dominant mode of inheritance. This clinical case demonstrates the need for gastroenterological and genetic examinations in the presence of lesions on the oral mucosa and the vermillion border of the lips to confirm or exclude Peutz-Jeghers syndrome.