– A progressive, hematologic neoplastic disease of the plasma cells.
Causes and Incidence
The etiologic factors are not clearly understood, but chromosomal abnormalities, genetic factors, viruses, and chronic antigen stimulation have been implicated as probable contributors. An important risk factor is occupational exposure to petroleum products, asbestos, or radiation. Multiple myeloma is a relatively rare disease that occurs primarily in those over 40 years of age and peaks around age 60. Men and women are equally affected, but the disease rate for blacks is 14 times that of whites. More than 13,000 cases are diagnosed in the United States each year, with 9,400 deaths.
Multiple myeloma involves an abnormal growth and proliferation of plasma cells and the development of single or multiple plasma cell tumors in the bone marrow. This leads to mass destruction of bone marrow and bone throughout the body. Plasma cells also produce an M protein immunoglobulin that coats the RBCs and inhibits the production of effective antibodies; this can lead to anemia. Metastasis is via the lymph nodes to the liver, kidneys, and spleen.
Early symptoms are nonspecific and include fatigue, weakness, anorexia, and weight loss. These are followed by complaints of bone pain, particularly in the back and thorax, and frequent bacterial infections, particularly pneumonia and anemia. Later manifestations include thrombocytopenia and leukopenia; urinary changes; changes in cognitive, sensory, and motor functions; pathologic fractures and vertebral collapse; spinal cord compression; and paraplegia.
The disease is progressive, and currently there is no cure. Life expectancy is tied to the extent of disease at time of diagnosis; the median survival rate is 2 to 3 years. Complications include infection, hyperuricemia, hypercalcemia, pyelonephritis, renal failure, and GI bleeding.
The diagnosis is made based on one or more of the following criteria: plasma cell infiltration above 10% in bone marrow; a monoclonal spike on serum electrophoresis; radiographic visualization of osteoporosis and osteolytic lesions; soft-tissue plasma cell tumors.
Chemotherapy is the primary treatment; antiinfective drugs for bacterial infections; allopurinol for hyperuricemia; corticosteroids for hypercalcemia.
Radiation in chemotherapyresistant disease and for palliation of bone pain; bone marrow transplantation has been used with limited success; ambulation maintained as long as possible; physical therapy to maintain function; fracture precautions; adequate hydration to prevent dehydration associated with proteinuria; transfusions for anemia; monitoring for bleeding episodes; precautions against exposure to infections; emotional support for adaptation to chronic, terminal disease.