Introduction
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare
hematological malignancy with dismal prognosis. With difficulty in
diagnosis, BPDCN was used in the 2008 World Health Organization (WHO)
classification for the first time and became a distinct entity in 2016
WHO classification [1]. Recently, the presence of four out of five
characteristic markers of BPDCN, namely, CD4, CD56, CD123, CD303, and
TCL1, has been shown to aid in the accurate diagnosis of BPDCN [2].
Skin lesions commonly occur in a majority of patients with BPDCN, and
blasts of BPDCN are suggested to arise from pre-malignant hematopoietic
precursor clones [3]. Thus, patients with systemic lesions were
treated with conventional chemotherapies for acute lymphoblastic
leukemia, acute myeloid leukemia, or non-Hodgkin’s lymphoma, sometimes
followed by autologous or allogeneic hematopoietic cell transplantation
as a consolidation therapy [4]. However, its clinical and biological
heterogeneous characteristics make its clinical management difficult
[5]. Herein, we describe the case of a patient who suddenly
developed leukemic form of BPDCN accompanied with CALReticulin
(CALR ) mutation arising from myelodysplastic/myeloproliferative
neoplasms with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T)
without cutaneous lesion, showing severe tumor lysis syndrome (TLS)
immediately after the induction therapy.