Multiple myeloma is a malignant tumour disease of the bone marrow in which the plasma cells have degenerated. Unlike other cancers, such as breast or skin cancer, with multiple myeloma there is therefore no tumour that the patient can feel or even see. So it is sometimes hard to understand exactly what lies behind the disease. This video explains how multiple myeloma develops in the body, exactly what happens and the effects of multiple myeloma on the metabolism.