Langerhans cell histiocytosis (LCH) is a dendritic cell (DC) neoplasm defined by the presence of pathologic cells with Langerhans cell features that are positive for CD1a, Langerin (CD207) and S100 protein.1 The disease varies widely in clinical presentation from localized involvement of a single bone to a fatal disseminated life-threatening disease involving risk organs such as liver, spleen, or hematopoietic system.2 Bone is the commonest area of involvement in about 80% of patients, which can be painful and associated with significant morbidity from pathologic fractures. The gene discussed is CD207; the disease is Langerhans cell histiocytosis.