Monoclonal B cell lymphocytosis: clinical and population perspectives

Monoclonal B Cell Lymphocytosis (MBL) refers to clones of CLL-like cells that exhibit CLL characteristics that fall short of the numbers required for CLL diagnosis. Data from large CLL kindreds document increased prevalence of MBL suggesting a genetic contribution to its etiology. The molecular features that favor progression of MBL to CLL are poorly understood but an elevated B-cell count is a risk factor for progression. An important consideration when evaluating volunteers from CLL families who are willing to donate bone marrow is that MBL be ruled out since the MBL donor clone could result in a second CLL in the recipient. Further studies of MBL are needed to identify the molecular features and how they evolve during progression.