Multiple Myeloma

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Overview

Multiple myeloma is a cancer that develops in plasma cells, which are types of white blood cells in bone marrow (the spongy tissue inside bones). Plasma cells normally produce proteins called antibodies, and they are part of the immune system, the body’s natural defense against infections. Cancerous plasma cells are called myeloma cells. In people with multiple myeloma, the myeloma cells multiply uncontrollably and, in time, collect in bone marrow, solid parts of bone and occasionally in other organs.

As these cells reproduce, they suppress the growth of healthy white blood cells in bone marrow, as well as red blood cells and blood platelets. Like normal plasma cells, myeloma cells also make antibodies, resulting in an abnormally high number of these proteins in blood. When myeloma cells collect in solid bone, they cause bone lesions (holes in bone). About 90% of people with multiple myeloma have bone lesions when diagnosed with the disease.

In an effort to better understand the causes of this disease, researchers are studying plasma cell DNA to find out why plasma cells mutate (change) into cancerous myeloma cells. Studies have found that most people who have multiple myeloma have genetic mutations in their plasma cells. For example, research has shown that many myeloma cells sometimes have abnormalities involving chromosomes 11, 13, 14 and 17.

Risk Factors

Researchers have also identified certain factors that could increase the risk of developing multiple myeloma, including age, race, gender, weight and monoclonal gammopathy of undetermined significance MGUS. (See Table 1.)

Symptoms and Diagnosis

People with multiple myeloma may not have symptoms early in the course of the disease, and doctors may just monitor the condition until specific symptoms appear. Because the overgrowth of myeloma cells suppresses the growth of healthy white blood cells, multiple myeloma can cause recurrent infections and fevers, especially pneumonia, sinus infections, infections of the kidneys or bladder, skin infections and shingles. Due to a reduction in red blood cells, multiple myeloma can cause anemia with symptoms of fatigue (feeling very tired), weakness and shortness of breath. Because of insufficient blood platelets, people with multiple myeloma may bruise and bleed easily and have frequent nosebleeds or bleeding gums.

Bone pain, especially in the back, ribs, pelvis and skull, is a common symptom of multiple myeloma. The pain is caused by bone damage and osteoporosis (thinning of the bone), which can lead to bone fractures. The pain often gets worse at night and with movement. If the myeloma affects the spine, vertebrae (bones that make up the spine) can collapse, causing nerve pain. People with advanced disease may lose inches from their height from compressed vertebrae.

Other symptoms may include kidney damage or kidney failure and weakness or numbness in the legs. A condition called hypercalcemia (high calcium levels in blood) may not only cause kidney damage but also weight loss, mental confusion, excessive thirst and urination, drowsiness, constipation or nausea.

To diagnose this disease, doctors perform a physical exam and take a medical history, then order blood and urine tests to look for a protein antibody known as the M protein, with the M standing for monoclonal. The M protein is also used to monitor the effectiveness of treatment for this disease. Blood tests are also used to check for kidney function, calcium levels and anemia.

Your doctor may also order a bone marrow biopsy, in which a small amount of marrow is removed by needle from the hip bone under local anesthesia. A pathologist then examines the tissue under a microscope. In addition, your doctor may order a biopsy of fat around your abdomen to check for amyloidosis, a condition marked by an accumulation of M proteins in organs and tissues.

Other tests may include bone x-rays, magnetic resonance imaging (MRI) to look for myeloma cells and plasma cell tumors known as plasmacytomas, computed tomography (CT) scans to look for tumors or abnormalities in soft tissues and, rarely, a positron emission tomography (PET) scan or integrated PET-CT scan to create images of organs and tissues for evaluation. A test called fluorescence in situ hybridization (FISH) may be done to look for changes in chromosomes in the myeloma cells.

Table 1. Risk Factors for Multiple Myeloma