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.

  1. Osteoclasts are attracted to areas of worn-out bone.
  2. The activity of the osteoclasts creates a cavity in the bone; this process is known as bone resorption.
  3. Osteoblasts are attracted to the cavity in the bone.
  4. The osteoblasts fill in the cavity with a matrix or framework for new bone.
  5. 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.