The Primary objective of this study is to compare serum levels of Macrophage-Colony Stimulating Factor (M-CSF) in a population of patients with multiple myeloma (MM), in a population of patients with Monoclonal Gammopathy of Undetermined Significance (MGUS) and in a control population.

Inclusion Criteria:

For the multiple myeloma group

• confirmed diagnosis of de novo multiple myeloma according to the International Myeloma Working Group criteria
• bisphosphonate therapy for more than 60 days,
• signature of the informed consent form,
• patients over the age of 18 years. For the monoclonal gammopathy of undetermined significance (MGUS) group
• confirmed diagnosis of MGUS according to the International Myeloma Working Group criteria
• signature of the informed consent form,
• patients over the age of 18 years. For the healthy control group
• signature of the informed consent form,
• subjects over the age of 18 years.

Exclusion Criteria:

• patients with thyroid or parathyroid disease,
• osteomalacia, rheumatoid arthritis, Paget's disease, osteoporosis,
• bisphosphonate therapy for less than 60 days,
• absence of informed consent,
• patients under the age of 18 years.