Localized blastic plasmacytoid dendritic cell neoplasm associated with progressive clonal hematopoiesis and myelodysplastic syndrome.

Clonal hematopoiesis is highly prevalent in elderly patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), and around 20% of BPDCN patients have an associated myeloid malignancy. We present a patient with localized BPDCN and concomitant myelodysplastic syndrome (MDS), previously followed for several years due to clonal cytopenia of unknown significance. Compared targeted next-generation sequencing (NGS) of the skin tumor and sequential bone marrow samples showed shared variants in ASXL1 and TET2 with a de novo NRAS variant in both BPDCN and MDS compared to preceding bone marrow samples. These findings illustrate a shared clonal origin of BPDCN and MDS resulting from progressive clonal hematopoiesis.