LCH lesions feature granulomatous collections of immature CD1a+ langerin/CD207+ DC (‘LCH cells’) presumed to be pathologic [8], [9], [10], admixed with abundant eosinophils [11], polyclonal T cells including abundant FoxP3+ CD4+ T cells [12], activated macrophages and osteoclast-like multinucleated giant cells [13]. This evidence concerns the gene CD1A and Langerhans cell histiocytosis.