Types of Multiple Myeloma

Multiple myeloma is a cancer of the plasma cells in the bone marrow, the soft, spongy tissue found inside most bones. Plasma cells are a type of white blood cell that make antibodies (immunoglobulins) to protect your body from infection. When you have an infection, your bone marrow produces more plasma cells and immunoglobulins to fight it.

In multiple myeloma, plasma cells change into cancerous cells (myeloma cells), which grow out of control. This uncontrolled growth leaves less room for healthy white blood cells, red blood cells and platelets. Abnormal immunoglobulins made by myeloma cells cannot properly fight infection.

Two Main Types of Multiple Myeloma

There are two main types of multiple myeloma:

• Active multiple myeloma: Active multiple myeloma has signs and symptoms.
• Smoldering multiple myeloma (SMM): Also called asymptomatic myeloma, smoldering myeloma is a precursor or early sign that someone may develop active multiple myeloma. SMM may take years to turn into active multiple myeloma. In some cases, people with SMM do not develop active multiple myeloma.

Types of Active Multiple Myeloma

The five primary types of active multiple myeloma are named after the abnormal immunoglobulins made by the myeloma cells. IgG myeloma is the most common type of multiple myeloma, followed by IgA myeloma. The other three types – IgE, IgD and IgM – are fairly rare.

In addition, two other types of active multiple myeloma are:

• Light chain myeloma: Also called Bence Jones myeloma, light chain myeloma occurs when the myeloma cells make too many light chain proteins. This type of myeloma does not produce an abnormal immunoglobulin.
• Non-secretory myeloma: This is a rare type of multiple myeloma that does not make abnormal immunoglobulins or light protein chains.

Conditions Related to Multiple Myeloma

Certain disorders that affect plasma cells can sometimes develop into multiple myeloma or occur at the same time as multiple myeloma. These conditions often do not cause symptoms and may not require treatment.

Plasma cell disorders (also called plasma cell dyscrasias) associated with multiple myeloma include:

• Solitary plasmacytoma: This is a condition where abnormal plasma cells form a tumor in one bone or one location in the body. Rarely, the tumor can grow outside the bone. Solitary plasmacytoma is often treated with radiotherapy. People who have a solitary plasmacytoma are monitored with blood testing in case they should develop multiple myeloma at a later time.
• MGUS (monoclonal gammopathy of unknown significance): MGUS is a noncancerous condition in which raised levels of abnormal proteins (monoclonal protein or M protein) are found in the blood, but no other signs of multiple myeloma are present. MGUS can lead to such illnesses as IgM myeloma and Waldenstrom’s macroglobulinemia, which is a slow-growing type of non-Hodgkin lymphoma.
• AL Amyloidosis: About 10 to 15 percent of people with multiple myeloma also develop a condition called amyloid light-chain (AL) amyloidosis. AL amyloidosis occurs when light protein chains break off plasma cells, stick to one another, and collect in the kidney, heart, liver or other organs. This condition is associated with a poorer outlook in people who have multiple myeloma, especially when the light protein chains accumulate in the heart.