Discussion
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare myeloid malignancy with non-pruritic, violaceous, and papulo-nodular skin lesions, as well as the involvement of the bone marrow and lymph nodes. The WHO’s 2016 classification of hematological neoplasms recognizes BPDCN as an unique acute leukemia entity. BPDCN has been reported in infants and children, even though it primarily affects older persons with a median age of 65 years. It is typically characterized by involvement of the skin that rapidly evolves and compromise organs such as bone marrow, lymph nodes, viscera, and, to a lesser extent, the central nervous system (CNS)[3].
With just a few research reports to date, the etiology and pathophysiology of BPDCN are largely unclear. BPDCN is frequently linked with a complicated karyotype, numerous tumor suppressor gene deletions, and abnormalities in the DNA methylation or chromatin remodeling pathways.[4]. In the case of Congenital Blastic Plasmacytoid Dendritic Cell Neoplasm, Kiriko Tokuda et al. described an infant with CLTC-ALK Fusion, which is considered a primary event[5].
In various epithelial and myeloid cells, the lysine-specific methyltransferase 2C (KMT2C/MLL3) is a possible tumor suppressor. KMT2C has also played a tumor suppressor role in acute myeloid leukemia (AML) and urothelial carcinogenesis in mice[6-7]. Its involvement in BPDCN carcinogenesis, however, is mainly unknown. Toya T et al. reported the first MLL-ENL rearrangement in a 45-year-old male patient in 2012[8]. In 2015, Naery Yang et al. said the first pediatric case of BPDCN with a KMT2A (MLL)-MLLT1  rearrangement[9]. Four juvenile patients of BPDCN with KMT2C gene mutation were recently described by Chan Liao et al., emphasizing the possible critical roles of KMT2 family genes in BPDCN[10].
Our study reports the first newborn BPDCN patient with KMT2C gene duplication. It is crucial to understand the pathophysiology of this rare disease, and more research into the gene expression profile and pathogenesis of BPDCN in pediatric patients may drastically enhance prognosis.