[Osteocalcin and anomalies of cellular immunity in rheumatoid polyarthritis]

Spinal and peripheral skeletal demineralisation is sometimes observed in rheumatoid arthritis (RA). Numerous studies have shown the role of osteoclasts in its genesis, but few studies have been conducted to demonstrate a functional anomaly of osteoblasts. Synthesized by osteoblasts, osteocalcin enables to approach the osteoblastic activity, through titration of its serum level. In 31 patients suffering from erosive classical RA, we titrated the serum osteocalcin. In 9 cases, we found a definite decrease of the serum osteocalcin levels. There was a statistically significant difference between these 9 patients and the 21 others, in the presence of anomalies of the CD4/CD8 lymphocytic ratio, the presence of extra-articular manifestations, a high level of rheumatoid factors, class IgM, with an immuno-enzymatic technique. On the contrary, there was no difference regarding the mean duration of the RA course, the mean age, calcemia, and alkaline phosphatases level. Thus, in the course of severe clinical and immunological rheumatoid arthritis, an anomaly of cellular immunity was observed associated with abnormal serum osteocalcin levels. The exact mechanism of this decrease remains to be specified. Other prospective studies are necessary to confirm this preliminary research.