Cutaneous Plasmacytosis Complicated with Chronic Lymphocytic Leukemia: A Case Report

Abstract In our case, we encountered a patient with a very rare complication who was diagnosed with chronic lymphocytic leukemia (CLL) combined with cutaneous plasmacytosis(C/SP). Cutaneous plasmacytosis is a rare and benign plasma cell proliferative disease, but a few reports suggesting that it has the potential to transform into malignant tumours. However, to date, there have been no reported cases of cutaneous plasmacytosis combined with chronic lymphocytic leukemia. Single cell RNA-seq analysis and clonotype tracking revealed co-expression of IGHV4-34 by malignant B-lymphocytes and monoclonal plasma cells. Interestingly, the presence of IGHV4-34, which is one of the most frequently used genes in CLL patients, has rarely been reported in plasma cell diseases. This indicated that there might be a similarity or homology between the malignant B-lymphocytes and monoclonal plasma cells in this particular patient.