Benign monoclonal gammapathy

Defining genomic events involved in the evolutionary trajectories of myeloma and its precursor conditions

All patients with a diagnosis of multiple myeloma (MM) have a preceding, asymptomatic expansion of clonal plasma cells, clinically recognized as monoclonal gammopathy of undetermined significance or smoldering multiple myeloma (SMM). While most patients with monoclonal gammopathy of undetermined significance have a very small rate of progression, SMM is a widely heterogeneous condition where a fraction of patients will progress to symptomatic MM rather quickly, while others will experience an indolent clinical course. The differentiation between progressive and stable precursor condition thus represents one of the most important unmet clinical needs in the MM community. The ability to identify patients at high-risk of progression before major clonal expansion and onset of end-organ damage would enable strategies for early prevention and perhaps more effective intervention. All proposed criteria to predict the progression of myeloma precursor conditions are built around indirect markers of disease burden and, therefore, are generally able to accurately identify only a small fraction of patients in whom progression to MM is already occurring. Leveraging whole genome and exome sequencing, it has been shown that patients with stable myeloma precursor conditions are characterized by either absence or lower prevalence of distinct genomic events that are detectable in progressive precursor condition years before the progression. In this review, we discuss evolving genomic concepts and tools; and their ability to differentiate myeloma precursor conditions into two distinct entities: one benign (monoclonal gammopathy of benign significance) and another malignant (asymptomatic multiple myeloma).

Advances in MGUS diagnosis, risk stratification, and management: introducing myeloma-defining genomic events

In the 1960s, Dr Jan Waldenström argued that patients who had monoclonal proteins without any symptoms or evidence of end-organ damage represented a benign monoclonal gammopathy. In 1978, Dr Robert Kyle introduced the concept of “monoclonal gammopathy of undetermined significance” (MGUS) given that, at diagnosis, it was not possible with available methods (ie, serum protein electrophoresis to define the concentration of M-proteins and microscopy to determine the plasma cell percentage in bone marrow aspirates) to determine which patients would ultimately progress to multiple myeloma. The application of low-input whole-genome sequencing (WGS) technology has circumvented previous problems related to volume of clonal plasma cells and contamination by normal plasma cells and allowed for the interrogation of the WGS landscape of MGUS. As discussed in this chapter, the distribution of genetic events reveals striking differences and the existence of 2 biologically and clinically distinct entities of asymptomatic monoclonal gammopathies. Thus, we already have genomic tools to identify “myeloma-defining genomic events,” and consequently, it is reasonable to consider updating our preferred terminologies. When the clinical field is ready to move forward, we should be able to consolidate current terminologies—from current 7 clinical categories: low-risk MGUS, intermediate-risk MGUS, high-risk MGUS, low-risk smoldering myeloma, intermediate-risk smoldering myeloma, high-risk smoldering myeloma, and multiple myeloma—to future 3 genomic-based categories: monoclonal gammopathy, early detection of multiple myeloma (in which myeloma-defining genomic events already have been acquired), and multiple myeloma (patients who are already progressing and clinically defined cases). Ongoing investigations will continue to advance the field.

Whole-genome sequencing reveals progressive versus stable myeloma precursor conditions as two distinct entities

Multiple myeloma (MM) is consistently preceded by precursor conditions recognized clinically as monoclonal gammopathy of undetermined significance (MGUS) or smoldering myeloma (SMM). We interrogate the whole genome sequence (WGS) profile of 18 MGUS and compare them with those from 14 SMMs and 80 MMs. We show that cases with a non-progressing, clinically stable myeloma precursor condition (n = 15) are characterized by later initiation in the patient's life and by the absence of myeloma defining genomic events including: chromothripsis, templated insertions, mutations in driver genes, aneuploidy, and canonical APOBEC mutational activity. This data provides evidence that WGS can be used to recognize two biologically and clinically distinct myeloma precursor entities that are either progressive or stable.

Immunoglobulin m monoclonal gammopathy of undetermined significance and smoldering Waldenström macroglobulinemia

Monoclonal gammopathy of undetermined significance of the immunoglobulin M class was diagnosed in 213 patients at the Mayo Clinic, 29 (14%) of whom developed lymphoma, Waldenström macroglobulinemia, or a related disorder over 1567 person-years of follow-up. The cumulative probability of progression was 10% at 5 years, 18% at 10 years, and 24% at 15 years, or approximately 1.5% per year. The concentration of serum monoclonal protein at diagnosis and the initial serum albumin value were the only independent predictors of progression with multivariate analysis. By contrast, during 285 person-years of follow-up, 34 (71%) of 48 patients with smoldering Waldenström macroglobulinemia (SWM) progressed to Waldenström macroglobulinemia (WM), which required therapy, along with amyloid light chain (AL) amyloidosis (1) and lymphoma (1). The cumulative probability of progression was 6% at 1 year, 39% at 3 years, 59% at 5 years, and 65% at 10 years. The percentage of lymphoplasmacytic cells in the bone marrow, size of the serum monoclonal (M) spike, and hemoglobin value were significant independent risk factors for progression.

Waldenström's macroglobulinemia in monozygotic twins

This paper reports a unique familial occurrence of Waldenström's macroglobulinemia (WM) in monozygotic twins. The determination of twin monozygosity has been performed by electrophoretic and immunological typing of genetic systems (erythrocyte blood groups, leucocyte antigens and serum protein polymorphism). The two monoclonal IgM differ one from the other by their light chain type and their idiotypic determinants. Although a genetic predisposition to WM exists in these twins, the gene recombination leading to idiotypic specificity and light chain assortment occurs independently of the monoclonal malignant involvement.

Prognostic factors and predictors of outcome of immunoglobulin M monoclonal gammopathy of undetermined significance

Monoclonal gammopathy of undetermined significance (MGUS) of the immunoglobulin M (IgM) class was diagnosed at our institution in 213 patients who resided in the 11 counties of southeastern Minnesota from 1960 to 1994. The median age at diagnosis was 74 years and the median concentration of serum M-protein was 1.2 g/dL. The 213 patients were monitored for 1567 person-years (median, 6.3 years), during which 71% died. During follow-up, non-Hodgkin's lymphoma (n = 17), Waldenstrom's macroglobulinemia (n = 6), primary amyloidosis (n = 3), and chronic lymphocytic leukemia (n = 3) developed in 29 patients (14%). The number of patients with progression to lymphoid neoplasms was 15.9 times that expected in the general population. The cumulative probabilities of progression to one of these disorders were 10% at 5 years, 18% at 10 years, and 24% at 15 years. The overall average risks for progression were approximately 1.5% per year. Rates of death resulting from other diseases (cardiovascular, cerebrovascular, etc.) were 31% at 5 years, 52% at 10 years, and 65% at 15 years. Multivariate analysis revealed that only the concentration of serum M-protein at diagnosis and the serum albumin value were independent predictors of progression. It was concluded that the patients with IgM MGUS should be followed indefinitely.

Long-term follow-up of IgM monoclonal gammopathy of undetermined significance

Little effort has been made to quantitate adverse outcomes of monoclonal gammopathy of undetermined significance (MGUS) of the immunoglobulin M (IgM) class, which progresses to lymphoma or Waldenström macroglobulinemia, whereas IgA and IgG MGUS progress to multiple myeloma, primary amyloidosis (AL), or a related plasma cell disorder. From 1960 to 1994, IgM MGUS was diagnosed in 213 patients in southeastern Minnesota. The end point was progression to lymphoma or a related disorder, as assessed with the Kaplan-Meier method. The 213 patients were followed up for 1567 person-years (median, 6.3 years per patient). Lymphoma developed in 17 patients (relative risk [RR], 14.8), Waldenström macroglobulinemia in 6 (RR, 262), primary amyloidosis in 3 (RR, 16.3), and chronic lymphocytic leukemia in 3 (RR, 5.7). The relative risk of progression was 16-fold higher in the patients with IgM MGUS than in the white population of the Iowa Surveillance, Epidemiology, and End Results Program. Cumulative incidence of progression was 10% at 5 years, 18% at 10 years, and 24% at 15 years. On multivariate analysis, the serum monoclonal protein and serum albumin concentrations at diagnosis were the only risk factors for progression to lymphoma or a related disorder. Risk for progression to lymphoma or a related disorder at 10 years after the diagnosis of MGUS was 14% with an initial monoclonal protein concentration of 0.5 g/dL or less, 26% with 1.5 g/dL, 34% for 2.0 g/dL, and 41% for more than 2.5 g/dL.

Long-term follow-up of IgM monoclonal gammopathy of undetermined significance

The current study was conducted to determine the risk of adverse outcomes among patients with monoclonal gammopathy of undetermined significance (MGUS) of the IgM class. Two hundred thirteen patients with IgM MGUS were identified in southeastern Minnesota from 1960 to 1994. The primary end point was progression to lymphoma or a related disorder assessed by the Kaplan-Meier method. Patients were followed for a total of 1,567 person-years (median, 6.3 years per subject). Seventeen patients developed lymphoma (relative risk [RR], 14.8) and six progressed to Waldenstrom's macroglobulinemia (RR, 262), while three developed primary amyloidosis (RR, 16.3) and three others had chronic lymphocytic leukemia (RR, 5.7). The relative risk of progression was 16-fold higher in the IgM MGUS patients compared to the white population of the Iowa Surveillance, Epidemiology, and End Results (SEER) program. The risk of progression of MGUS of IgM type to lymphoma or related disorders averaged 1.5% per year throughout the period of observation.

Waldenström's macroglobulinemia: clinical features, complications, and management

PURPOSE

To review the clinical features, complications, and treatment of Waldenström's macroglobulinemia, a low-grade lymphoproliferative disorder that produces monoclonal immunoglobulin (Ig) M.

METHODS

A review of published reports was facilitated by the use of a MEDLINE computer search and by manual search of the Index Medicus.

RESULTS

The clinical manifestations associated with Waldenström's macroglobulinemia can be classified according to those related to direct tumor infiltration, to the amount and specific properties of circulating IgM, and to the deposition of IgM in various tissues. Asymptomatic patients should be followed without treatment. For symptomatic patients, standard treatment consists primarily of oral chlorambucil; nucleoside analogs, such as fludarabine and cladribine, are effective in one third of previously treated patients and in up to 80% of previously untreated patients. Preliminary evidence suggests that anti-CD20 monoclonal antibody may be active in about 30% of previously treated patients and that high-dose therapy with autologous stem-cell rescue is effective in most patients, including some with resistance to nucleoside analogs.

CONCLUSION

Waldenström's macroglobulinemia has a wide clinical spectrum that practicing physicians need to recognize early to reach the correct diagnosis. When therapy is indicated, oral chlorambucil is the standard primary treatment, but cladribine or fludarabine can be used when a rapid cytoreduction is desirable. Prospective randomized trials are required to elucidate the impact of nucleoside analogs on patients' survival. A nucleoside analog is the treatment of choice for patients who have been previously treated with an alkylating agent.

Diagnostic applications of chromatography and capillary electrophoresis

Capillary electrophoresis (CE) equipped with a diode-array detector, and GC-MS have been used to determine diagnostic metabolites occurring in urine of patients with various metabolic disorders. The urine samples were injected directly onto the CE instrument without any pretreatment. GC-MS required extraction and derivatisation before separation. Identification of abnormal metabolites was based on migration times and characteristic diode-array spectra, or mass spectral library search when GC-MS was used. The CE method has previously been shown capable of diagnosing several metabolic diseases, and was now used on more difficult cases. CE readily diagnosed glyceric aciduria and the secondary metabolite in lysinuric protein intolerance, orotic acid. Methylmalonic aciduria required pressure elution in addition to high voltage to accomplish diagnosis. In mevalonic aciduria the characteristic metabolite had weak light absorption and the mevalonate peak also co-eluted with endogenous aromatic acids making diagnosis difficult. Both in the latter case and with the disorders glutaric aciduria I and glyceroluria, GC-MS was the method of choice. A possible role of CE in the routine system for diagnosing metabolic disorders, might be to use this method for pre-testing all urine samples. Samples with abnormal CE-profiles would subsequently be given high priority for more elaborate analysis with GC-MS and amino acid analyzer. In a different project a CE instrument designed for serum protein analysis was used to study sera from patients with myelomatosis. The method also allowed identification of the various immunoglobulins using immunosubtraction. Samples collected after diagnosis as well as many years prior to disease were available through the Janus-bank. This large serum bank comprises samples collected since 1973 at intervals from nearly 300000 blood donors. It was found that the monoclonal immunoglobulins characteristic of the disease started to appear in serum up to 15 years before clinical diagnosis.

Isolation and molecular characterization of the B cells producing the paraprotein in a case of benign monoclonal gammapathy in C57BL mice

Benign monoclonal gammapathy (BMG) is defined as a benign monoclonal B cell proliferative disorder characterized by the presence of a persisting component of homogenous immunoglobulins (H-Ig) in the serum. A possible role of antigenic stimulation in the development of BMG has been suggested. From a C57BL mouse, a murine model for BMG, we have isolated clonally related B cells in order to investigate the occurrence of somatic mutations in the variable heavy chain (VH) region of the genes of H-Ig-producing B cell clones. Therefore, B cells were immortalized by hybridoma technology. The hybridomas were screened for resemblance of the serum H-Ig component by Wieme agar electrophoresis, followed by immunoblotting and isoelectrofocusing. Clonal relationship was investigated by Southern blot analysis using a JH probe. In this way we isolated five hybridomas producing an IgG2a, kappa that was identical to the original serum H-Ig component according to testing with anti-idiotypic antisera. mRNA sequencing of four hybridomas showed only one base pair difference in the VH genes. This particular gene belonged to the J558 VH gene family. When compared to the most closely related known VH sequence, three base pair differences were found. The almost complete absence of base pair differences in the VH genes of the four sequenced hybridomas, compared with an independently derived hybridoma, suggests that the same germ-line VH gene has been used and that somatic mutations were infrequent in our BMG clone.

Age-related monoclonal gammapathies: clinical lessons from the aging C57BL mouse

In this article the long-held notion that benign monoclonal gammapathy (BMG) is a premalignant stage in the development of multiple myeloma (MM) is attacked. Jiri Radl argues that clinical and experimental observations indicate that they are separate entities which may be distinguished in the laboratory and which should be managed in radically different ways.

[Monoclonal gammopathies in Tunisia]

Protein electrophoresis and immunoelectrophoresis carried out on 4805 sera and 93 urine samples from Tunisian patients over 8 years, and a monoclonal protein was detected in 198 cases. The distribution of the monoclonal compounds to the clinical diagnosis was studied. 115 (58%) were classified as multiple myeloma (MK), 34 (17%) as alpha heavy chain disease (MCL a), 34 (17%) as monoclonal gammapathy associated to various diseases (GMOD), 11 (6%) as benign essential monoclonal gammapathies (GMBE), 4 (2%) as Waldenström's macroglobulinemia (MW). The relationship between the monoclonal immunoglobulin and the clinical diagnosis, the distribution of the monoclonal compounds according to the heavy chain class and the identification of the light chains were studied. The results obtained are in line with the principal data in literature concerning monoclonal gammapathy. However there is a particularity about monoclonal gammapathy observed in the Tunisian's population studied: Higher percentage of alpha heavy chain diseases, monoclonal IgD and monoclonal light chain. Lower percentage of monoclonal IgM in GMBE or GMOD, as in MW.

The spectrum of IgM monoclonal gammopathy in 430 cases

IgM monoclonal gammopathy consists of a broad spectrum of diseases, ranging from apparently benign to malignant conditions. In a long-term follow-up study of 430 patients in whom a monoclonal IgM serum protein had been identified, 242 (56%) had monoclonal gammopathy of undetermined significance, 71 (17%) had Waldenström's macroglobulinemia, 28 (7%) had lymphoma, 21 (5%) had chronic lymphocytic leukemia, 6 (1%) had primary amyloidosis, and 62 (14%) had other malignant lymphoproliferative diseases. More than two-thirds of the patients died, and the most common cause of death was a lymphoid malignant process. Almost a fifth of the patients with an apparently benign monoclonal gammopathy subsequently had a lymphoid malignant lesion (in one patient, more than 20 years after the detection of the serum M protein). The median duration of time from the recognition of the M protein until the development of a malignant lymphoid disease ranged from 4 to 9 years. An increased number of lymphocytes or plasma cells on bone marrow examination was not a reliable indicator of the likelihood of such an outcome. Thus, follow-up of these patients should be conducted indefinitely.