INTRODUCTION
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive malignancy caused by transformed plasmacytoid dendritic cells that overexpress interleukin-3 receptor subunit alpha (IL3RA) also known as CD123.1 Tagraxofusp-erzs (Stemline Therapeutics, Inc. NY) is a CD123-directed cytotoxin consisting of a recombinant human interleukin-3 fused to a truncated diphtheria toxin2 that was FDA-approved for BPDCN in 2018 for adults and children over 2 years of age.1 Here, we report a case of BPDCN recalcitrant to tagraxofusp-erzs, that responded successfully to off-label venetoclax (AbbVie Inc, IL and Genentech-USA, CA).
CASE PRESENTATION
A man in his late 70’s otherwise in good health developed an asymptomatic rash involving the back and the right knee. The rash began as pink patches that evolved into plaques and subsequently, the plaque on the right knee evolved into a tumor in the span of 3 months. Skin biopsy showed blastic plasmacytoid dendritic cell neoplasm (BPDCN). Bone marrow biopsy showed 22% blasts positive for CD123, CD56 and TCL1. Further workup was negative for systemic involvement.
The patient received 6 cycles of tagraxofusp-erzs but the skin lesions persisted. He was then started on chemotherapy regimen consisting of decitabine (antimetabolite analogue) and venetoclax (inhibitor of Bcl-2) and underwent three cycles. Skin lesions resolved and a follow up bone marrow biopsy showed normocelluar bone marrow with less than 1% of CD34 positive immature cells. Markers were negative for CD123, CD56 and TCL1 with no evidence of blastic plasmacytoid dendritic cells.
Venetoclax treatment conferred a favorable clinical response, disappearance of skin lesions and nearly complete resolution of the right knee tumor (Figure 1). Given the success of the treatment, the patient deferred bone marrow transplantation typically offered to patients with treatment-resistant BPDCN and he continues surveillance with oncology.
The patient received 6 cycles of tagraxofusp-erzs but the skin lesions persisted. He was then started on chemotherapy regimen consisting of decitabine (antimetabolite analogue) and venetoclax (inhibitor of Bcl-2) and underwent three cycles. Skin lesions resolved and a follow up bone marrow biopsy showed normocelluar bone marrow with less than 1% of CD34 positive immature cells. Markers were negative for CD123, CD56 and TCL1 with no evidence of blastic plasmacytoid dendritic cells.
Venetoclax treatment conferred a favorable clinical response, disappearance of skin lesions and nearly complete resolution of the right knee tumor (Figure 1). Given the success of the treatment, the patient deferred bone marrow transplantation typically offered to patients with treatment-resistant BPDCN and he continues surveillance with oncology.
