title: Prevalence and natural history of monoclonal and polyclonal B-cell lymphocytosis in a residential adult population.
abstract: BACKGROUND
  Monoclonal B-cells can be detected in the peripheral blood of some adults without B-cell malignancies, a condition recently termed monoclonal B-cell lymphocytosis (MBL). The risk of individuals with MBL progressing to a B-cell malignancy is unknown. Polyclonal B-cell lymphocytosis (PCBL) has not been systematically studied in the general population.
  
  
  METHODS
  We obtained lymphocyte subset counts on 1,926 residential adults aged 40-76 years in a series of environmental health studies between 1991 and 1994. We then conducted two follow-ups in 1997 and 2003 on consenting participants with B-cell lymphocytosis, which included nine participants with MBL. To ascertain the clinical implications of MBL, we reviewed medical records and death certificates.
  
  
  RESULTS
  The overall prevalence of MBL was 0.57% (11/1,926): nine cases at baseline and two additional cases identified at follow-up. Two (19%) MBL cases subsequently developed a B-cell malignancy; MBL persisted in the remaining nine cases (81%). All PCBL cases where no clone emerged regressed to normal B-cell counts over the follow-up period. MBL was significantly more frequent in residents near a hazardous waste site than in the control populations (age-adjusted OR 6.2; 95%CI 1.1-36.2).
  
  
  CONCLUSIONS
  MBL confers an elevated risk for developing a B-cell malignancy, although it occurs only in a minority of cases. PCBL is most often a transient state, but a monoclonal population can emerge and persist. Prospective studies are needed to distinguish stable from progressive forms of B-cell lymphocytosis and to clarify the etiologic role of environmental exposures.
authors.affiliation: Division of Health Studies, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia 30333, USA. yshim@cdc.gov
authors.forename: Youn K
authors.initials: YK
authors.lastname: Shim
authors.forename: Robert F
authors.initials: RF
authors.lastname: Vogt
authors.forename: Dan
authors.initials: D
authors.lastname: Middleton
authors.forename: Fatima
authors.initials: F
authors.lastname: Abbasi
authors.forename: Barbara
authors.initials: B
authors.lastname: Slade
authors.forename: Kyung Y
authors.initials: KY
authors.lastname: Lee
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Marti
mesh_terms: D000328:Adult; D000368:Aged; D001402:B-Lymphocytes / Q000276:immunology* / Q000473:pathology; D019070:Cell Lineage / Q000276:immunology; D002999:Clone Cells; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015448:Leukemia, B-Cell / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D018655:Lymphocyte Count; D008218:Lymphocytosis / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology*; D016393:Lymphoma, B-Cell / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011379:Prognosis; D014481:United States / Q000453:epidemiology