PLASMA cell dyscrasias refer to a spectrum of disorders characterized by the monoclonal proliferation of lymphoplasmacytic cells in the bone marrow and, sometimes, tissue deposition of monoclonal immunoglobulins or their components (Table 21-1). The disorders include multiple myeloma (MM) and Waldenström's macroglobulinemia, as well as rare conditions such as light-chain deposition disease (LCDD) and heavy-chain diseases (HCDs). Amyloidosis refers to a group of tissue deposition disorders, among which light-chain amyloidosis is a plasma cell dyscrasia. Monoclonal gammopathy of undetermined significance is an asymptomatic laboratory deviation that may evolve into one of the previously mentioned diseases.
Multiple myeloma is the most serious and prevalent plasma cell dyscrasia, affecting approximately four of 100 000 Americans each year (Table 21-2). The median age at onset is 60 years, and black persons are affected twice as often as white persons. Symptoms usually result from lytic bone disease, anemia, renal failure, and immunodeficiency.