Biochemical bone biomarkers in plasma cell dyscrasias.

Multiple myeloma (MM) is a haematological malignancy characterised by clonal plasma cell accumulation in the bone marrow, frequently resulting in myeloma bone disease. Disruption of bone homeostasis, driven by increased osteoclastic resorption and suppressed osteoblastic formation, leads to osteolytic lesions and skeletal-related events, contributing substantially to morbidity and mortality. Bone turnover markers (BTMs) provide a non-invasive means of assessing bone metabolism, with potential applications in disease monitoring, prognostication, risk stratification from monoclonal gammopathy of undetermined significance (MGUS) to MM and evaluation of response to myeloma and osteoporosis therapies. This review examines the clinical relevance of BTMs in plasma cell dyscrasias, including MM, MGUS and smouldering MM. Bone formation markers, such as bone-specific alkaline phosphatase and procollagen type I N-terminal propeptide, reflect osteoblastic activity, while resorption markers, including carboxy-terminal collagen crosslinks and deoxypyridinoline, indicate osteoclastic activity. Although several BTMs correlate with disease burden and progression, their routine clinical use is limited by biological variability, renal impairment and lack of assay standardisation. As myeloma therapies continue to evolve, further research is needed to define the role of BTMs alongside imaging and clinical risk models to optimise bone disease management.