Plasmacytoid Dendritic Cell Leukemia in Children

CD4(+)/CD56(+) malignancies tire rare hematologic neoplasms, which have recently been shown to represent the malignant counterpart of plasmacytoid dendritic cells (pDC). A 5-year-old boy initially presented with multiple subcutaneous lesions oil his upper and lower extremities. Skin biopsy results showed large atypical lymphoid cells in the dermis. The blast cells were stained with CD4 and CD56. In the bone marrow aspirate, 20% of the blast cells were found. The patient wits diagnosed as acute unclassified leukemia and received chemotherapy designed for the treatment of acute myeloid leukemia. He achieved a complete remission that lasted for 8 months. However, multiple subcutaneous lesions recurred 1 month after the end of the therapy, with increasing blast cells in his blood. Immunophenotypically, the blast cells were positive for CD2, CD4, CD7, and CD56, and negative for CD3, CD13, CD19, CD33, and CD34 antigens. The blast cells were positive for CD123 (interleukin-3 receptor Of. chain) and blood dendritic cell antigen-2, which are expressed oil pDC. The patient was diagnosed as acute leukemia derived from pDC. The CD4(+), CD56(+), CD3(-), CD13(-), CD19(-), CD33(-) profile is highly suggestive of this disease, and the CD123 and blood dendritic cell antigen-2 markers are useful in helping to diagnose pDC leukemia.