Abstract
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a malignancy with high frequency of skin involvement. A 39-year-old Caucasian female was suffering from weakness, myalgia, and skin eruption, which appeared during treatment of chlamydiosis with antibiotics in July 2016. Based on clinical presentation, laboratory investigations, and histological examination of skin and bone marrow biopsy, a diagnosis of BPDCN with the involvement of skin, bone marrow, and central nervous system was made. The patient was put on acute lymphoblastic leukemia-like chemotherapy and achieved complete remission in November 2016, the eruption regressed. In January 2017, allogeneic bone marrow transplantation from matched sibling was performed. Since May 2017, the cutaneous relapse with loss of CD56 expression has developed. This clinical case demonstrates the importance of laboratory tests. Histological examination helps to clarify a diagnosis of cutaneous lymphoma; however, a specific type of lymphoma needs immunohistochemical analysis. In our case, BPDCN at the initial stage presented like a systemic vasculitis.