JXG shares with LCH and other non-LCH disorders, such as Rosai-Dorfman and Erdheim-Chester, common somatic mutations in mitogen-activated protein (MAP) kinase, phosphoinositide 3-kinase (PI3K), and Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway genes such as CSF1R, KRAS, MAP2K1, and NRAS.11 This evidence concerns the gene PIK3CA and Langerhans cell histiocytosis.