Bone remodelling in monoclonal gammopathies of uncertain significance, symptomatic and nonsymptomatic myeloma.

In order to characterize the abnormalities of bone remodelling in the various stages of plasma cell disorders, we studied 60 patients (29 monoclonal gammopathies of uncertain significance (MGUS), 13 stage I myeloma, 18 stage III myeloma). We carried out histomorphometric study of bone biopsies in 34 patients and measurement of osteocalcin and the calciuria/creatinine ratio. Bone remodelling was approximately normal (BV/TV:21.2 +/- 7, ES:4.1 +/- 2, OS:16.5 +/- 10) in MGUS. Stage I myeloma was characterised by parallel increases in resorption surfaces and osteoid surfaces (BV/TV:18 +/- 5, ES/BS:7.4 +/- 3.5, OS/BS:24.8 +/- 11.5), of the ca/cr ratio and osteocalcin. In stage III myeloma, resorption surfaces and the ca/cr ratio showed an even greater increase while osteoid surfaces, osteocalcin and trabecular bone volume decreased (BV/TV 13.6 +/- 6, ES/BS:12.1 +/- 6, OS/BS:13.6 +/- 8.3). Osteocalcin and osteoid surfaces were correlated (r = 0.5). There was a positive correlation between osteocalcin and the number of plasmocytes in stage 1 myeloma (r = 0.64) and a negative correlation in stage III myeloma (r = 0.9). Bone remodeling was normal in MGUS; bone remodelling grew with a parallel increase of formation and resorption in stage I; bone resorption increased while bone formation decreased in stage III myeloma.