title: Diagnostic criteria for monoclonal B-cell lymphocytosis.
abstract: Very low levels of circulating monoclonal B-cell subpopulations can now be detected in apparently healthy individuals using flow cytometry. We propose the term 'monoclonal B-cell lymphocytosis' (MBL) to describe this finding. The aim of this document is to provide a working definition of MBL for future clinical, epidemiological and laboratory studies. We propose that the detection of a monoclonal B-cell population by light chain restriction is sufficient to define this condition in individuals not meeting the diagnostic criteria for other B-lymphoproliferative disorders. The majority of individuals with MBL will have cells that are indistinguishable from chronic lymphocytic leukaemia (CLL). However, this blood cell clonal expansion of CD5+ or CD5- B-lymphocytes is age-dependent and immunophenotypic heterogeneity is common. Longitudinal studies are required to determine whether MBL is a precursor state to CLL or other B-lymphoproliferative disease in a situation analogous to a monoclonal gammopathy of undetermined significance and myeloma. Future studies of MBL should be directed towards determining its relationship to clinical disease, particularly in individuals from families with a genetic predisposition to developing CLL.
authors.affiliation: Center for Biologics Evaluation and Research (CBER), US Food and Drug Administration (FDA), NIH, Bethesda, MD, USA. gemarti@helix.nih.gov
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Marti
authors.forename: Andy C
authors.initials: AC
authors.lastname: Rawstron
authors.forename: Paolo
authors.initials: P
authors.lastname: Ghia
authors.forename: Peter
authors.initials: P
authors.lastname: Hillmen
authors.forename: Richard S
authors.initials: RS
authors.lastname: Houlston
authors.forename: Neil
authors.initials: N
authors.lastname: Kay
authors.forename: Thérèse A
authors.initials: TA
authors.lastname: Schleinitz
authors.forename: Neil
authors.initials: N
authors.lastname: Caporaso
mesh_terms: D000293:Adolescent; D000328:Adult; D018941:Antigens, CD19 / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology; D018956:CD5 Antigens / Q000032:analysis; D002999:Clone Cells; D018450:Disease Progression; D020022:Genetic Predisposition to Disease; D006801:Humans; D016130:Immunophenotyping; D016393:Lymphoma, B-Cell / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D008875:Middle Aged; D017455:Receptors, IgE / Q000032:analysis; D013997:Time Factors
chemical_list: D018941:Antigens, CD19; D018956:CD5 Antigens; D017455:Receptors, IgE