Contributor: Gordon K. Klintworth
Multiple myeloma is a plasma cell neoplasm [plasma cell neoplasm] that involves multiple sites in the skeleton. Lymph nodes and other sites such as the orbit and skin may also be affected. Crystals and other shaped deposits of immunoglobulin may accumulate in the cornea and be the initial presenting manifestation of multiple myeloma [keratopathy - tactoid]. Men are affected more often than women and in Western countries it accounts for 1% of cancer deaths. The blood contains an M component and IL-6 is elevated in the serum in persons with active disease. Bence Jones protein is often present in the blood and urine. The immunoglobulin levels are depressed and result in an increased susceptibility to recurrent infection, especially bacterial infection by Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli. These infections are the most frequent cause of death. Osteolytic lesions in the bone are widespead and prominent and cause bone pain and patholologic fractures. Hypercalcemia and an anemia that is both normochromic [anemia - normochromic] and normocytic [anemia - normocytic] [normochromic normocytic anemia] are features. Complications include systemic amyloidosis, renal failure from calcium nephropathy [nephropathy - calcium]. Particular in the early disease multiple myeloma may be difficult to differentiate from plasmacytoma and  MGUS. Rarely multiple myeloma evolves into plasma cell leukemia [leukemia - plasma cell]. Normal bone marrow cells are replaced by plasma cells that are often atypical with multiple nuclei, prominent nucleoli, and globules of intracytoplasmic immunoglobulin.