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Plasma cell dyscrasias are a spectrum of progressively more severe monoclonal gammopathies in which a clone or multiple clones of pre-malignant or malignant plasma cells over-produce and secrete into the blood stream a myeloma protein, i.e. an abnormal monoclonal antibody or portion thereof. The exception to this rule is the disorder termed non-secretory multiple myeloma; this disorder is a form of plasma cell dyscrasia in which no myeloma protein is detected in serum or urine of individuals who have clear evidence of an increase in clonal bone marrow plasma cells and/or evidence of clonal plasma cell-mediated tissue injury. Here, a clone of plasma cells refers to group of plasma cells that are abnormal in that they have an identical genetic identity and therefore are descendants of a single genetically distinct ancestor cell.
At one end of this spectrum of hematological disorders, detection of one of these myeloma proteins in an individual's blood or urine is due to a common and clinically silent disorder termed MGUS, i.e. monoclonal gammopathy of undetermined significance. At the other end of this spectrum, detection of the myeloid protein is due to a hematological malignancy, i.e. multiple myeloma, Waldenström macroglobulinemia, or other B cell-associated neoplasm, that has developed, often in a stepwise manner, from their MGUS precursors.
The clinical importance of understanding this spectrum of diseases is that it can be used to: a] advise individuals on the likelihood of their condition progressing to a malignant phase; b] monitor individuals for the many complications that may occur at any stage of the dyscrasias so that they can be treated to avoid or reduce their clinical impacts; and c] monitor patients for transitions to malignancy so that the malignancy can be treated at an early stage when treatment results are best. Unless otherwise noted, the advice and monitoring given here are those recommended by the International Myeloma Working Group in 2014 and updated in 2016.