The main characteristic of monoclonal gammopathies (MG) is the presence of an increased amount of both electrophoretically and immunologically homogeneous immunoglobulins (M component). According to the WHO classification, monoclonal gammopathies are classified among the non-Hodgkin's lymphomas as 'plasma cell dyscrasias'. The unknown behaviour state, so-called MGUS (monoclonal gammopathy of undetermined significance), is distinguished from the malignant diseases. We investigated the frequency and features of MG and MGUS by reviewing the serum immunochemistry protein analyses between 1998 and 2004. Among 18 642 analyses, MG was found in 1983 cases (10.39%) derived from one or more samples of 416 patients. Case histories of 340 patients were analysed. A malignant lymphoproliferative disease was proved in 171 cases, while in 169 cases the behaviour of the gammopathy was unknown. In 65 cases, the disease was possibly not related to MG. Mean follow-up time of the 65 patients with MGUS was 42 (9-81) months. During the follow-up period seven patients progressed into a malignant lymphoproliferative disorder - mean probability of the malignant transformation was 3.07%/year and it occurred more frequently in the presence of immunoglobulin A isotype. There was no correlation between the progression of the disease and other laboratory findings. Besides the analyses of MG-related diseases, we focus on the malignant transformation of MGUS and on the importance of regular clinical and laboratory control examinations.
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