Malignant transformation in IgM monoclonal gammopathy of undetermined significance

The epidemiology of Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare subtype of non-Hodgkin lymphoma characterized by the presence of lymphoplasmacytic lymphoma (LPL) in the bone marrow accompanied by a monoclonal immunoglobulin type M (IgM) in the serum. WM was first described only 80 years ago and became reportable in the US as a malignancy in 1988. Very little systematic research was conducted prior to 2000 to characterize incidence, clinical characteristics, risk factors or diagnostic and prognostic criteria, and there were essentially no WM-specific clinical interventional trials. Since the inaugural meeting of the International Workshop in Waldenström's Macroglobulinemia (IWWM) in 2000, WM has become the focus of a steadily increasing and productive body of research, engaging a growing number of investigators throughout the world. This introductory overview provides summary of the current understanding of the epidemiology of WM/LPL as a backdrop for a series of consensus panel recommendations arising from research presented at the 11th IWWM.

Paraproteinemic neuropathies

The term paraproteinemic neuropathy refers to a heterogeneous group of neuropathies, which share the common feature of a homogeneous immunoglobulin in the serum. The presence of a monoclonal gammopathy indicates an underlying clonal B-cell expansion, which may appear in the context of a lymphoproliferative disorder. If a neoplastic origin of the gammopathy is identified, the treatment should be targeted to the neoplasm. In most patients, however, the monoclonal gammopathy is not associated with malignant haematological disorders, and is defined as monoclonal gammopathy of undetermined significance.

Prevalence, clinical aspects, and natural history of IgM MGUS

BACKGROUND

Waldenström macroglobulinemia (WM) and chronic lymphocytic leukemia (CLL) are related B-cell cancers that share several clinical and biological features. Both WM and CLL have associated precursor conditions: monoclonal gammopathy of undetermined significance (MGUS) of immunoglobulin M (IgM) type and monoclonal B-cell lymphocytosis (MBL), respectively. Recently, a case of MBL with an IgM MGUS was reported, suggesting a close biological relationship between these entities. While much is known about MGUS overall, investigations of IgM MGUS specifically have been fragmentary.

METHODS

In this article, we review data on the prevalence, clinical aspects and natural history of IgM MGUS, and focus on identifying gaps in our understanding of the complex relationships among B-cell malignancies and their precursors.

RESULTS

There appears to be marked heterogeneity in the prevalence of IgM MGUS across populations. However, studies have varied in definition, design, laboratory methods, and endpoints. IgM MGUS differs from non-IgM MGUS in certain respects, including prevalence across racial groups, rate of progression, and pattern of malignant outcomes. There are limited data regarding the coincident occurrence of IgM MGUS and MBL.

CONCLUSIONS

Future studies incorporating both protein electrophoresis and flow cytometry are needed to define the underlying spectrum and causes of precursor development, risk factors for progression, and markers that distinguish low- and high-risk precursor patients.

Waldenström macroglobulinaemia and IgM monoclonal gammopathy of undetermined significance: emerging understanding of a potential precursor condition

Previously thought to be best described as a plasma cell disorder, Waldenström macroglobulinaemia (WM) is now understood to be a distinct clinicobiological entity. WM shares B-cell origin and certain other features with both chronic lymphocytic leukaemia (CLL) and multiple myeloma (MM). WM and CLL arise from B-cells at discrete stages in their maturation process, and MM arises from B-cells that have fully differentiated into plasma cells. While MM has a well-known precursor condition, monoclonal gammopathy of undetermined significance (MGUS), CLL and WM may also have associated precursor states, monoclonal B-cell lymphocytosis (MBL) and IgM MGUS, respectively. This review explores the features that link or distinguish these haematolymphoid malignancies, with special attention to emerging data regarding IgM MGUS and its unique relationship to WM, and identifies important gaps in our understanding of the putative precursor conditions, MBL and IgM MGUS.

Cytogenetic aberrations in neuropathy associated with IgM monoclonal gammopathy

The occurrence and nature of cytogenetic aberrations in polyneuropathy associated with IgM monoclonal gammopathy was determined. Therefore, interphase fluorescence in situ hybridization (FISH) was applied in 22 patients with polyneuropathy associated with IgM monoclonal gammopathy, multiplex ligation-dependent probe amplification (MLPA) assay in 18 of these patients and genome-wide-array-based comparative genomic hybridization (CGH) in eight of these 18 patients. Four patients had 10-20% and one patient had 30% B cells with IgH rearrangements; one patient had additional loss of 14qter; one patient had amplification of 6p and loss of 6q. Cytogenetic aberrations may be found in one third of the patients with neuropathy associated with IgM monoclonal gammopathy and are mainly associated with indolent Waldenstrom's Macroglobulinemia.

Long-term Evaluation of Three Multiple-Case Waldenström Macroglobulinemia Families

PURPOSE

Because the clinical significance of immunoglobulin abnormalities reported in relatives of familial Waldenström macroglobulinemia (WM) patients is unknown, we initiated a follow-up study of three WM families originally evaluated 27 years previously.

EXPERIMENTAL DESIGN

Of 29 eligible first-degree relatives of WM patients, 27 (93%) had originally participated in clinical and electrophoretic evaluations. We re-contacted all participants for prospective follow-up electrophoretic analysis and other studies.

RESULTS

Initially, five relatives had IgM monoclonal gammopathy (IgM MG), and four had IgM polyclonal gammopathy (PG). Twenty-two relatives (81%) were re-evaluated. Median follow-up was 17 years (range, 7-27). At re-contact, all IgM MG persisted or progressed, including three that evolved to WM. Among the four with PG, two new IgM MG cases developed. Overall, seven relatives (26%) had IgM MG, and five (18%) had IgM PG.

CONCLUSIONS

Although based on small numbers, this study provides the longest comprehensive follow-up of WM families to date. IgM MG seems to be a phenotypic marker of WM susceptibility in some families and may have a high risk of progression to WM. IgM PG may also be important in WM families. These observations require validation in larger studies and, if confirmed, may be used to identify a cohort (relatives with IgM MG) for future prevention strategies.

Investigation of monoclonal gammopathy of undetermined significance: a single-centre study

Summary 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 1,983 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.

Current therapies for neuromuscular manifestations of paraneoplastic syndromes

The neuromuscular manifestations of paraneoplastic disorders result in diverse syndromes that may also occur in patients without cancer. In general, treatment of these disorders is the same whether or not there is an underlying malignancy. However, when the disorder is believed to be paraneoplastic, the main concern should be prompt detection and treatment of the tumor, as this has been shown to offer the best chance for neurologic stabilization or improvement. The paraneoplastic neuromuscular disorders can be divided into two main categories: those that are directly mediated by antibodies and those that are believed to result from other immune-mediated mechanisms, including cytotoxic T-cell responses with or without association with specific antibodies. For disorders in which the antibodies are pathogenic, therapy is aimed at removing the antibodies. For the other disorders, adjuvant therapies are for the most part empiric and include a variety of immunosuppressant and immunomodulatory agents.

IgM paraproteinaemic neuropathies

PURPOSE OF REVIEW

To conduct a critical review of recent studies on the pathogenesis and treatment of IgM paraproteinaemic neuropathies and analyse their implication for patient management.

RECENT FINDINGS

A better definition and classification of IgM monoclonal gammopathies has led to recommendations on therapeutic strategies for these patients, particularly for those with the asymptomatic form of Waldenström macroglobulinemia. Studies on the pathogenetic role of IgM paraprotein in neuropathy have led to the identification of a novel antibody reactivity against trisulfated heparin disaccharide, which was associated with painful, predominantly sensory, axonal distal neuropathy. Pathological studies on patients with axonal polyneuropathy and no antibody reactivity of the IgM paraprotein have shown that vasculitis may play an important role in this form of neuropathy, as possibly confirmed by its positive response to steroids. A number of open pilot trials have addressed the effect in IgM paraproteinaemic neuropathies of the humanized monoclonal antibody (rituximab) directed against the CD20 antigen. Even if the results of these studies are less promising than initially hoped, they provide evidence that rituximab may be effective in some patients with this neuropathy.

SUMMARY

New insights into the pathogenesis of axonal forms of IgM paraproteinaemic neuropathy have derived from the identification of novel antibody reactivity and of vasculitis. The latter finding may justify the use of steroids, otherwise ineffective in IgM paraproteinaemic neuropathy. Rituximab has opened the way to more selective and apparently safer immune therapies for this neuropathy, but its efficacy needs to be confirmed by randomized controlled trials.