title: Monoclonal gammopathy in Iceland: a population-based registry and follow-up.
abstract: The term monoclonal gammopathy (MG) signifies the benign or malignant clonal growth of B lymphocytes. In the present study, monoclonal gammopathy of unknown significance (MGUS) was defined as those patients with no identified haematological malignancy. A database was constructed of all 713 MG patients in Iceland between 1976 and 1997 and compared with the Icelandic Cancer Registry. The age-standardized incidence per 100 000 of MG was 10.3 for males and 8.6 for females, calculated for the whole period, rising steadily from 5.8 (men) and 4.9 (women) during the 5-year period 1976-80 to 14.7 (men) and 12.5 (women) during the last 5 year period. Age-standardized incidence rates were very low for subjects under 50 years of age, then increased with age from 11 and 17 per 100 000 at 50-54, to 169 and 119 per 100 000 at age 80-84, for men and women respectively. No association was detected between MG and non-haematological malignancies, neither retrospectively nor prospectively. Haematological malignancy was diagnosed in 209 (29.3%) cases before the recorded finding of MG or within the same calendar year, leaving 504 (70.7%) patients diagnosed with MGUS. Of these, 51 (10%) progressed to multiple myeloma or Waldenström's macroglobulinaemia after a mean interval of 3.8 years; mean follow-up was 7.4 years, median 6 years. The most common immunoglobulin (Ig) class was IgG (55%), followed by IgM (32%) and IgA (13%). MGUS was a highly significant risk factor for developing haematological malignancies and the risk was significantly greater for MG of the IgA class compared with either IgG or IgM.
authors.affiliation: Molecular and Cell Biology Research Laboratory, Icelandic Cancer Society, Reykjavík, Iceland. helgam@krabb.is
authors.forename: Helga M
authors.initials: HM
authors.lastname: Ogmundsdóttir
authors.forename: Vilhelmína
authors.initials: V
authors.lastname: Haraldsdóttir
authors.forename: Guethmundur
authors.initials: G
authors.lastname: M  Jóhannesson
authors.forename: Guethríethur
authors.initials: G
authors.lastname: Olafsdóttir
authors.forename: Kristín
authors.initials: K
authors.lastname: Bjarnadóttir
authors.forename: Helgi
authors.initials: H
authors.lastname: Sigvaldason
authors.forename: Hrafn
authors.initials: H
authors.lastname: Tulinius
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008998:Monoclonal Gammopathy of Undetermined Significance / Q000453:epidemiology*; D009101:Multiple Myeloma / Q000453:epidemiology; D012042:Registries; D012306:Risk; D017678:Sex Distribution; D008258:Waldenstrom Macroglobulinemia / Q000453:epidemiology