Langerhans cell histiocytosis (LCH) is a rare neoplastic disease of dendritic cells that most commonly occurs in children, but can also affect adults. The article describes the case of a 34-year-old man with multisystem LCH who had synchronous involvement of the esophagus, stomach, and colon. Endoscopic examination revealed characteristic findings: barnacle-like plaques in the esophagus, ulcerated nodules in the stomach, and subepithelial masses in the colon. During resection, a new endoscopic feature of “mucosal fragmentation” was identified, in which the mucosa suddenly detached to reveal white tumor tissue resembling fish flesh. Histological examination confirmed the presence of LCH with positivity of CD1a, S100 and langerin (CD207) markers and detection of BRAF V600E mutation. This case is the first systematic description of simultaneous involvement of several parts of the gastrointestinal tract in an adult patient with LCH. Distinctive endoscopic patterns can help in early diagnosis and better biopsies in unusual clinical situations.