نظرة عامة
Smoldering multiple myeloma (SMM), also called smoldering myeloma, is a condition in which changed plasma cells build up in the bone marrow. Plasma cells are white blood cells that help fight infection. The changed cells make protein that is not typical. It is called monoclonal protein, or M protein.
SMM is more advanced than the plasma cell condition known as monoclonal gammopathy of undetermined significance (MGUS) but it is not active multiple myeloma. SMM does not cause the organ damage or other changes that define active multiple myeloma.
SMM is sometimes described as a very early form of blood cancer. It also may be described as a condition that comes before active multiple myeloma. Although SMM involves changed plasma cells, it is not active multiple myeloma because it has not caused the damage or other changes that define active disease.
Some people have low-risk SMM that may remain stable for years. Others have high-risk SMM and are more likely to develop active multiple myeloma. Learning that you have SMM can bring worry. Regular testing helps your healthcare team understand your risk and decide whether monitoring or treatment may be right for you.
People with high-risk SMM have a greater chance of developing active multiple myeloma. Some healthcare professionals describe high-risk SMM as an early form of multiple myeloma that has not caused symptoms.
الأعراض
Smoldering multiple myeloma causes no symptoms. There are no recognized early-stage or late-stage SMM symptoms.
Symptoms that appear during monitoring may be due to another condition. But they also may mean that SMM has worsened, also called progressed, to active multiple myeloma. Possible symptoms include:
- New or ongoing bone pain, especially in the back, ribs or hips.
- A broken bone that happens with little or no injury.
- Fatigue, weakness or shortness of breath.
- Frequent or serious infections.
- Nausea, constipation, confusion or thirst that is not usual.
- Passing less urine or having swelling in the legs.
- New numbness, tingling or weakness.
Bone lesions, which are areas of damaged or changed bone, do not occur with SMM. If myeloma causes a bone lesion, the condition may be diagnosed as active multiple myeloma.
A rash is not a typical symptom of SMM. Tell your care team about a new rash, especially if it develops after starting treatment. Neuropathy, which can cause numbness, tingling or burning pain, is not typical of SMM either.
When to seek care
Contact your care team right away if you have a new symptom, even if it seems mild. Symptoms that need medical review include:
- Lasting or worsening bone pain.
- A possible broken bone.
- Increasing fatigue or shortness of breath.
- Frequent infections or a fever.
- Changes in urination or new swelling.
- Numbness, tingling or weakness.
- Confusion, thirst that is not typical, nausea or constipation.
When to seek emergency care
Get emergency care for severe back pain with sudden leg weakness or numbness, trouble walking, or loss of bladder or bowel function. These symptoms may be caused by pressure on the spinal cord.
الأسباب
The exact cause of smoldering multiple myeloma is not known.
SMM develops when one group of plasma cells grows more than expected and produces M protein. Many people first have monoclonal gammopathy of undetermined significance (MGUS), a less advanced plasma cell condition. MGUS may remain stable. Or it may progress to SMM or active multiple myeloma.
Researchers continue to study the genetic and biological changes that allow plasma cells to grow and SMM progress.
عوامل الخطورة
The factors that cause a person to develop smoldering multiple myeloma are not fully understood. Factors linked with SMM include:
- MGUS. SMM may develop during follow-up for MGUS.
- Older age. SMM is most often diagnosed in older adults.
- Sex at birth. SMM happens more often in men.
Most people with these factors do not develop SMM. There is no known lifestyle change that reliably prevents it.
المضاعفات
Progression to active multiple myeloma
The main complication of smoldering multiple myeloma is that it may worsen, also called progress, to active multiple myeloma. Progression means the plasma cells have increased or changed enough to cause organ damage or other findings that define active disease.
Active multiple myeloma can cause:
- Bone damage or broken bones.
- Anemia, which means having too few red blood cells.
- Kidney damage.
- Hypercalcemia, which means high calcium levels in the blood.
- Frequent or serious infections.
SMM does not always progress. In a systematic review, about 23% of people across all risk groups progressed within 2 years and about 60% progressed within 10 years. Among people classified as high-risk, about 45% progressed within 2 years and about 86% progressed within 10 years. These numbers describe groups of people. They cannot predict whether or when SMM will progress in one person.
Amyloidosis
SMM and amyloidosis are different plasma cell conditions. A diagnosis of SMM requires that there be no evidence of light-chain amyloidosis, also called AL amyloidosis. If testing finds AL amyloidosis, the diagnosis and treatment approach are different.
Myelodysplastic syndromes
SMM and myelodysplastic syndromes are different conditions that affect bone marrow. Current evidence does not show that SMM causes myelodysplastic syndromes. Low blood cell counts can have many causes, so they need medical evaluation.