[Systemic versus local demineralization in rheumatoid arthritis : Insights into the bone]

Inflammatory rheumatic diseases, such as rheumatoid arthritis (RA), are characterized by local and systemic bone demineralization. Local demineralization is manifested in the periarticular region of the inflamed joints, particularly at the metacarpophalangeal and metatarsophalangeal joints. Local demineralization shows a significant correlation with inflammatory activity, whereas systemic osteoporosis, predominantly affecting the spine and hip, is typically associated with a prolonged disease duration, glucocorticoid treatment and immobilization. The receptor activator of the nuclear factor-kB ligand (RANKL)/osteoprotegerin (OPG) system and the Wnt signaling pathway play a pivotal role in regulating bone metabolism and are themselves negatively influenced by inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-6. The diagnostics include both imaging procedures and procedures for bone mineral density measurement, employing techniques such as high-resolution peripheral quantitative computed tomography (HR-pQCT) and dual energy X‑ray absorptiometry (DXA). These are used for quantification of the bone mineral density. The objective of therapeutic approaches is to reduce disease activity and modulate signaling pathways in order to slow down demineralization and reduce the risk of fractures.