A unique case of a myelodysplastic/myeloproliferative neoplasm with distinct histiocytic and dendritic cell outgrowths

Erdheim-Chester disease (ECD) and Langerhans cell histiocytosis (LCH) are rare histiocytic disorders with multisystem involvement. Both are considered distinct entities with characteristic clinical, radiological, and pathological features. A limited number of cases have been reported of patients with ECD in association with LCH. We report a case, for the first time to our knowledge, of a patient with ECD, coexisting LCH, a third histiocytosis of less defined lineage, and a myelodysplastic/myeloproliferative neoplasm (MDS/MPN).