Langerhans cell histiocytosis and Erdheim-Chester disease, a continuity?

Erdheim-Chester disease and langerhans cell histiocytosis are two rare diseases separate on clinical, radiological and histological aspects. However, several cases involving both entities have been described. A 70-year-old man had a central diabetes insipidus, xanthelasmas, retroperitoneal fibrosis and osteosclerosis of the legs suggestive of Erdheim-Chester disease. Bone biopsy showed langerhans cell histiocytosis CD1a positive with the presence of BRAF V600E mutation. The patient was treated with vemurafenib with a good clinical course. The literature review finds forty observations linking the two diseases that may suggest a pathophysiological link, especially with the hematopoietic myeloid stem cell CD34+. The term inflammatory myeloid neoplasm was advanced.