Clinical manifestations of monoclonal gammopathy of undetermined significance

Monoclonal gammopathies are a heterogeneous group of diseases and conditions characterized by the proliferation of a single clone of plasma cells secreting immunoglobulins of homogeneous structure (M-protein). They occur with a frequency of 5-7 cases per 100, 000 population, predominantly in individuals over 50 years of age, especially those older than 70 years. The diagnosis of monoclonal gammopathy of undetermined significance (MGUS) is considered valid when monoclonal IgM paraprotein is detected in the blood at a concentration of less than 30 g/l, lymphoplasmacytic infiltration of the bone marrow is less than 10% of the examined trephine biopsy volume, and there are no signs of target organ damage that could be attributed to a lymphoproliferative disorder. Monoclonal immunoglobulin most often serves as a biomarker of clonal cell proliferation. In addition to plasma cell neoplasms (multiple myeloma, lymphoplasmacytic lymphoma, AL amyloidosis, and others), detection of paraprotein secretion reguires differential diagnosis with other lymphoproliferative disorders, myelodysplastic syndrome, Gaucher disease, systemic connective tissue diseases, liver disorders, sarcoidosis, Sjogren's syndrome, cold agglutinin disease and neurological conditions. B- cells dysfunction may also occur in various infectious and autoimmune diseases, immunodeficiency states, and solid tumors. The availability of serum protein electrophoresis with detection of an "M-gradient" within the compulsory medical insurance at the State Budgetary Institution of the Rostov Region "Consultative and Diagnostic Center "Zdorovye" in Rostov-on-Don" since 2019 has made it possible to assess the prevalence of this laboratory phenomenon and has increased physician awareness of the need for hematology consultation for such patients. The clinical course of MGUS is diverce: long-term benign paraproteinemia (>5 years) with possible transformation into a hematologic malignancy may occur, as well as manifestation of an oncohematological disease (AL amyloidosis), and, rarely, transient paraproteinemia associated with cytomegalovirus hepatitis. The manifestation of monoclonal gammopathies with a wide range of symptoms and syndromes necessitates a comprehensive diagnostic approach and interdisciplinary collaboration among physicians of various specialties.