Introduction: Langerhans cell histiocytosis (LCH) is an abnormal clonal proliferation of Langerhans cells secondary to immune process, mutation of oncogene or genetic predispositions. It preferentially affects bone, lung and skin. The incidence is 2–6 cases per million per year. Prognosis is variable and depends on number and location of lesions, and impact of the initial treatment. Oral lesions may be the first sign of LCH as illustrated by the present case. Observation: A 24-year-old male consulted first for severe gingival inflammation, teeth mobilities and alveolar bone loss with a suspicion of LCH. A pulmonary involvement was secondarily revealed by tomodensitometry. Histological examination, from gingival biopsy, confirmed the diagnostic of LCH, showing cells positive for the anti-CD1A antibody. The patient was managed by oral surgery and chemotherapy approaches. Alveolar bone loss significantly reduced. But 2 years and a half after the diagnosis, a recurrence was noted and managed by surgical approach. After a three-year follow-up, no recurrence was noted. Conclusion: Oral lesions can be inaugural manifestations of LCH. The dentist has an essential role in the early detection of these lesions.