Newly Diagnosed Patients:
How Myeloma Affects Normal Bone Processes
Myeloma cells cause bone destruction by interfering with the normal process of bone growth and remodeling. Bone remodeling is a continual process that occurs in all healthy bones. The process involves the rebuilding of fatigued, or worn-out, bone through the well-balanced activity of two types of bone cells: osteoclasts, cells that break down bone, and osteoblasts, cells that promote bone growth. The following steps occur in normal bone remodeling.
- Osteoclasts are attracted to areas of worn-out bone.
- The activity of the osteoclasts creates a cavity in the bone; this process is known as bone resorption.
- Osteoblasts are attracted to the cavity in the bone.
- The osteoblasts fill in the cavity with a matrix or framework for new bone.
- New bone forms to fill the cavity.
The rapid growth of myeloma cells increases the production of substances that activate osteoclasts and also inhibits the production of osteoblasts. As a result, the breakdown of bone exceeds its formation, leading to bone pain, an increased likelihood of bone fracture, and the release of an excess amount of calcium in the bloodstream, a condition known as hypercalcemia.