Langerhans Cell Histiocytosis and Myelodysplastic Syndrome: A Casual Association or a Pathogenetic Correlation?

Background: Langerhans Cell Histiocytosis (LCH) is a rare disease in adults, characterized by a proliferation of abnormal Bone Marrow (BM) derived Langerhans Cells (LCs) in single or multiple organs. The Myelodysplastic Syndrome (MDS) represents a group of clonal disorders, characterized by dysplasia in two or more lineages. We try to clarify if LCH and MDS have the same clonal origin or if they are two independent neoplasms. Methods: We report a case of a female, with a4-month history of pruriticred to brownish papules, localized on trunk and proximal limbs, covered by crusts. She was diagnosed with LCH, with involvement of skin, lymph nodes, lungs and liver. Two months later, by studying a progressive pancytopeniathe diagnosis of a high-risk MDS was done. We did a molecular examination of BM to detect the presence of BRAF (V600E) mutation and a flow cytometrycell sorting to detect the presence of mutation in plasmacytoid dendritic cells, myeloid dendritic cells and CD34+ cells. Results: The BRAF mutation (V600E) was detected in BM cells as well asinpurified plasmacytoid dendritic cells and it wasn´t detected in purified myeloid dendritic cells. The patient died 8 months later with a bacterial infection. Conclusion: We found no evidence of clonal relationship between LCH and MDS. These results don´t support the hypothesis of a common stem cell origin for the two neoplasms.