Purpose: To evaluate the incidence of monoclonal gammopathies (MG) in our sanitary district, to determine the associated diseases, and to analyse their clinical course along a period of over 20 years.
Patients and methods: The study comprised 1,203 patients with MG, of whom 397 had multiple myeloma (MM) and 806 had non-myelomatous monoclonal gammopathies (NMMG). All patients were diagnosed and followed in the Department of Haematology of the Miguel Servet Hospital, in Zaragoza, between january 1971 and december 1992. The SWOG criteria for MM and those proposed by Kyle for NMMG were followed in all cases. The explorations performed in every patient included physical examination, x-ray skeletal survey, peripheral blood study, bone-marrow aspiration or biopsy, study of liver and kidney function. The protein study carried out in blood and urine included agarose gel electrophoresis and electroimmunofixation. Descriptive statistics and determination of actuarial accumulated risk for the transformation of MG undetermined significance (MGUS) into malignant MG (MMG) were also carried out.
Results: Incidence: The yearly incidence of MG remained stable up to 1985 as 25 new cases; from that time on, a 30-40% yearly increase was noticed, this increase being mainly related with NMMG. Distribution: MM included 397 patients (33.0%), while 806 cases (67.0%) had NMMG. In these last were included those MG associated to haematologic malignancies, 139 cases (11.5%) or to other diseases, 286 cases (23.8%), as well as MGUS, 347 cases (28.9%), and in 34 cases the MG acquired a transient character. The mean age in the series was 62.1 years, ranging between 2 and 92, and the M/F ratio was 1.13. IgG was the commonest immunochemical type, 762 cases (63.3%), followed by IgA, 214 cases (17.8%) and IgM, 114 cases (9.5%) Multiple MG appeared in 3.8% of the cases, 64 instances, with monoclonal component present only in urine. Of the MG associated to blood diseases, the highest frequency corresponded to lymphoproliferative disorders (74.8%), and of those MG associated to other disease, neoplasms and liver diseases were the commonest. The second place in frequency corresponded to MGUS, in which a periodical follow-up with median duration of 37.8 months was kept in 93.6% of the cases. Ten patients evolved into MMG within a median of 60 months, having an actuarial accumulated risk of 4.5%, 15% and 26% at 5, 10 and 15 years, respectively.
Conclusions: (1) MG are relatively frequent disorders, representing an important number of interventions for a general haematology department each year. (2) MM is the commonest of all MG, followed by MGUS. (3) The clinical importance of MM lies upon the possibility of evolving into MMG. In this series, ten patients developed MMG within a median of 60 months and having an actuarial risk of 4.5%, 15% and 26%, respectively, at 5, 10 and 15 years.