CD207 (Langerin) is a calcium-dependent lectin that serves as a defining marker for Langerhans cells and certain dendritic cell subsets. The protein functions as a pattern recognition receptor with mannose-binding specificity and plays critical roles in antigen uptake and processing 1. CD207+ cells are pathognomonic for Langerhans cell histiocytosis (LCH), a clonal myeloid disorder characterized by constitutive MAPK pathway activation, most commonly through BRAFV600E mutations 21. These pathogenic CD1a+/CD207+ cells accumulate in lesions ranging from single-system disease to life-threatening multisystem involvement with potential neurodegeneration 2. Beyond its role as a histiocytic marker, CD207+ dendritic cells function as epithelial-associated antigen-presenting cells in healthy tissues, where they are enriched at airway epithelial interfaces and contribute to immune responses 3. In inflammatory conditions, CD207+ dendritic cells can mediate Th2 polarization in asthma when stimulated by IL-25 3 and participate in persistent inflammatory responses in conditions like post-COVID anosmia 4. The clinical significance of CD207 extends to its use as a diagnostic marker for histiocytic disorders and as a potential therapeutic target in MAPK-driven diseases 1.