MONOGAMMAPATHY OF UNDETERMINED SIGNIFICAT ION AND OSTEOPOROSIS - AN ASSOCIATION OR A COINCIDENCE

OBJECTIVES: Osteoporosis is common in subjects over 70 years of age. L ikewise, the incidence of monogammapathies of undetermined significati on (MGUS) increases with age. We conducted this sutudy to determine wh ether the biological and histomorphometric characteristics of osteopor osis in patients with MGUS are different from those in primary osteopo rosis and to ascertain whether any cause and effect relationships coul d exist between MGUS and osteoporosis, excluding signs of active myelo ma. PATIENTS AND METHODS: Serum and urinary phosphorus and calcium, hi stomorphometric measurements, hormone levels and serum cytokines (IL1, IL6 and TNF alpha) were determined in 7 patients (mean age 71.8 years , 2 men and 5 women) with MGUS associated with osteoporosis with verte bral fractures (OF) and compared with those in 7 osteoporosis patients without MGUS matched for age, sex, and osteoporosis severity and 7 ot her age and sex matched patients with MGUS without OS. The MGUS+PS pat ients were followed for 9 years (4.5 to 20) so slowly progressive myel oma could be excluded. RESULTS: Cytokine levels were the same in the t hree groups of patients but MGUS+OP patients had higher urinary calciu m levies (ca/cr = 0.21 +/- 0.08 vs 0.12 +/- 0.1 (OF) and 0.13 (MGUS); p=0.04), decreased osteocalcin levels (7 +/- 4.6 ng/ml vs. 12 +/- 4 (O F) and 11.5 +/- 5 (MGUS); p=0.01) and increased surface resorption (8 +/- 1.4 vs. 3.6 +/- 1.2 (OP) and 5.5 +/- 1.7 (MGUS); p=0.05). DISCUSSI ON: it has been demonstrated that MGUS in patients with increased reso rption and lower osteocalcin levels frequently progresses to active my eloma. The question is raised as to whether, in certain cases of MGUS, in situ stimulation of bone cells by monoclonal plasma cells could ex ist without ongoing transformation to active myeloma.