- Has the pathology look of JXG but overlaps with LCH lineage
- Can have concomitant LCH
- Adults in 5th-7th decade
- Skin involvement 20%, clinically similar to xanthelasma and eruptive xanthoma
- Pathology similar to JXG
- BRAF mutation common
- Skeletal, cardiac, lung, CNS involvement
- Most common presentation is bone pain
- Osteosclerotic lesions in long bones
- IFN alpha first-line treatment
- Mortality >30%