The syndrome is defined by the presence of; both of two major criteria, peripheral neuropathy and a clonal plasma cell dyscrasia (increased bone marrow plasma cells in ~67% of cases; ≥1 plasmacytoma in ~33% of cases); at least one other major criteria (Castlemans disease, sclerotic bone lesions, elevated serum levels of the cytokine VEGF); and at least one minor criterion (organomegaly, extravascular volume overload [e.g. ascites, edema, pleural effusion, and/or pericardial effusion], endocrinopathy [i.e. hypogonadism, defects in the hypothalamic–pituitary–adrenal axis], skin changes, papilledema, and/or hematological manifestations [i.e. thrombocytosis or polycythemia]). The monoclonal protein in POEMS patients is typically identified as IgA or IgG which in >95% of cases contains a λ chain that is restricted to either of two members of the V lambda 1 subfamily viz., IGLV1-40*01 and IGLV1-44*01 (there are 29 other members in the V lambda family). That is, the myeloma protein in POEMS is almost invariably a clonal λ light chain variant. Deletion of chromosome 13 and chromosomal translocations but not increases in chromosome number have also been reported to occur in POEMS patients.Patients with 1 or 2 isolated plasmacytomas have been successfully treated with targeted radiotherapy to obtain relief of symptoms and sometimes complete remission of disease. (Isolated plasmacytomas may regress spontaneously.) Patients with >2 plasmacytomas or symptomatic disseminated disease have been treated with chemotherapy often followed by autologous stem-cell transplantation; these treatments have been found to reduce symptoms of the disease and lead to long-term partial remissions of disease.
In general, progression to one of these malignant outcomes occurs at a rate of 2% to 3% per year. Individuals with higher serum IgM or lower serum albumin levels progress at faster rates than those with normal levels of these parameters. Light chain MGUS
Individuals diagnosed with light chain MGUS typically do not express detectable levels of an IgG, IgA, IgD, IgE, or IgM intact myeloma protein in their blood. Rather, they overexpress a monoclonal, aberrant free κ (i.e. kappa) or λ (i.e., lambda) immunoglobulin light chain. For diagnosis, the κ and λ free light chains are quantified by immunological methods and the ratio of κ to λ light chains is used to detect unbalanced light chain synthesis that is indicative of a monoclonal light chain plasma cell dyscrasia. Light chain MGUS is defined as a disorder in which a serum κ to λ free light chain ratio falls outside the normal range of 0.26–1.65 (mean =0.9) provided that it is not associated with: a) any of the CRAB criteria, b) a bone marrow plasma cell count of 10 or a higher percentage of nucleated cells, c) evidence of amyloid deposition (see Light chain deposition disease), and d) an accumulation of 0.5 or more grams of the monoclonal light chain in the urine over a 24-hour period.