High Frequency of Monoclonal B-cell Lymphocytosis with a High Prevalence of Biclonal Cases in the Colombian Population

The World Health Organization (WHO) defines monoclonal B-Cell Lymphocytosis (MBL) as the presence in Peripheral Blood (PB) of monoclonal populations of B-Lymphocytes (BL) of up to 5x109/L, with the phenotype of Chronic Lymphocytic Leukemia (CLL) typical, CLL atypical, or non-CLL, in the absence of B symptoms or clinical manifestations related to chronic B-Cell Lymphoproliferative Disorders (B-CLPD). It is classified as Low Count (LC) (<500 clonal BL/μL) and High Count (HC) (>500 clonal BL/μL) [1]. It has been described in up to 12% of the healthy adult population [1], a proportion that increases in relatives of patients with CLL/Small Lymphocytic Lymphoma (SLL) to around 15% [2]. It is usually a more frequent entity (28.5%) in people with Hepatitis C virus (HCV) [3] infection, and it tends to persist for a long time (90% of cases) with a progression rate of the MBL-HC to clinical manifest B-CLPD between 1-4% per year [1,2]. Currently, it continues to be an entity under study since its possible evolution to CLL or another B-CLPD is clearly unknown [4].