IgM Monoclonal Gammopathy Research Articles

Ibrutinib in Anti-MAG Neuropathy with Waldenstrom Macroglobulinemia (P10-5.010)

<h3>Objective:</h3> NA <h3>Background:</h3> Anti-myelin associated glycoprotein (MAG) neuropathy constitutes 5% of CIDP like presentation and is a disabling paraproteinemic neuropathy with variable response to treatment. <h3>Design/Methods:</h3> 69-year-old male with eleven-year history of tingling in the hands and then feet presented with worsening dexterity and numbness in 2012. Examination showed distal wasting, weakness of toe and ankle movements, length dependent pan sensory loss, and plantar flexion, wide-based gait and absent reflexes. Nerve conduction studies (NCS) showed primary demyelinating length dependent polyneuropathy. Work up revealed IgM monoclonal gammopathy and anti MAG antibody titer of 66,000. He was diagnosed with Waldenstrom Macroglobulinemia (WM). Initial treatment with IVIg showed minimal response. Symptoms stabilized on Rituximab between 2013 and 2016 and treatment was temporarily stopped. In January 2020 due to re-emergence of symptoms, Rituximab was restarted. But he continued to worsen. Repeat NCS/EMG in 2021 did not show improvement. Ibrutinib was started in April 2022 due to electroclinical worsening of neuropathy, but he has not had a clinical response. His IgM gammopathy has resolved although his kappa/lambda ratio and anti-MAG titer remain elevated. We plan on repeat NCS/EMG and ultrasound of the peripheral nerve for further characterization and assessment of the neuropathy. <h3>Results:</h3> Rituximab, currently the most commonly prescribed treatment for anti-MAG neuropathy, provides benefit in less than 50% of patients. Smaller studies show efficacy of Ibrutinib in anti-MAG antibody neuropathy. Our patient tolerated Ibrutinib but failed to show clinical improvement. Anti-MAG antibody titers do not correlate with severity of disease or with paraprotein levels, and the mechanism of action of Ibrutinib in anti-MAG neuropathy is not well understood. The lymphoplasmacytes producing anti-MAG antibodies may have a survival advantage, explaining refractoriness of anti-MAG neuropathy to treatment. <h3>Conclusions:</h3> Larger studies are needed to understand the efficacy of Ibrutinib. Drugs targeting anti-MAG antibodies and lymphoplasmacytes need to be developed. <b>Disclosure:</b> Dr. Mahuwala has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for alexion. The institution of Dr. Mahuwala has received research support from UCB, . The institution of Dr. Mahuwala has received research support from Alexion . The institution of Dr. Mahuwala has received research support from argenx . The institution of Dr. Mahuwala has received research support from immunovant. The institution of Dr. Mathur Kumaraswamy has received research support from Woolsey Pharmaceuticals. Dr. Thandampallayam Ajjeya has nothing to disclose. Dr. Pervin has nothing to disclose.

Highly Sensitive Detection Method of CXCR4 Tumor Hotspot Mutations by Drop-Off Droplet Digital PCR in Patients with IgM Monoclonal Gammopathies

CXCR4 mutations impact disease presentation and treatment outcomes in Waldenström macroglobulinemia. Current techniques used for CXCR4 mutation detection have a number of limitations. The aim of the present study was to develop and analytically validate a novel droplet digital PCR (ddPCR) assay for the simultaneous detection of five of the most common CXCR4 mutations in bone marrow (BM). In silico novel primers and probes designed for simultaneous detection of five hotspot mutations of CXCR4 were first performed. Experimental conditions were optimized, and the assay was analytically validated. The developed assay was further applied in 95 BM samples from patients with IgM gammopathy, 7 BM samples from patients with non-IgM gammopathy and 12 PBMCs from healthy donors, whereas a direct comparison study of Sanger sequencing and allele-specific PCR was performed by using 95 and 39 identical patient tumor DNA samples, respectively. The drop-off ddPCR assay is a robust, cost-effective, highly sensitive, and highly specific screening tool for CXCR4 mutations. Of 95 patients with IgM gammopathy samples, 27 had at least one CXCR4 mutation in their BM samples. With Sanger sequencing, 12 of the 95 samples tested positive, whereas the direct comparison of the developed assay with allele-specific PCR revealed substantial agreement. The clinical performance of the developed assay will be prospectively evaluated in a large number of patients, and the applicability of this assay will be further evaluated.

Ibrutinib response in a patient with refractory mixed essential cryoglobulinemia.

A 74-year-old male presented with fatigue, parasthesiae, Raynaud's phenomena, visual disturbances, and recurrent lower extremity rash (left). Investigations revealed an elevated serum cryoglobulin, rheumatoid factor >1320 IU/ml (ref. <15 IU/mL), undetectable C4, and C3 of 25 mg/dL (ref. 87–200 mg/dL). A small amount of IgM kappa monoclonal protein (M spike of 2.5%) and polyclonal IgG were identified by immunofixation. A diagnosis of mixed (Type II) cryoglobulinemia was made. Testing for Hepatitis B and C was negative. Positron emission/computed tomography (PET-CT) showed no evidence of lymphoma. Although the bone marrow appearance raised suspicion for Waldenstrom macroglobulinemia (WM), testing for MYD88 L265P mutation, which is commonly associated with this disorder, was negative. Of note, scattered CD20-positive B-cells comprised only ∼5% of bone marrow cellularity. The patient's rash gradually evolved into large ulcers over bilateral medial malleoli. Despite treatment with immunosuppression, rituximab, and plasmapheresis, they expanded to 9.3 × 8.9 × 0.3 cm on the left and 8.6 × 5.6 × 0.4 cm on the right (middle), requiring extensive use of opioids and significantly interfering with patient's mobility. A second bone marrow biopsy was again suggestive of WM. However, the frequency of abnormal B-cells was even lower (1.7%), likely reflecting prior therapy. Therefore, B-cells were purified by flow sorting using antibodies against CD19, CD20, and CD38 prior to molecular testing. Critically, this approach revealed the presence of MYD88 L265P mutation, supporting the diagnosis of WM and justifying therapy with Ibrutinib, a Bruton kinase inhibitor which is highly effective in this disease. Starting Ibrutinib 420 mg daily was a clear turning point in the patient's clinical course. After just a few days, he reported a drastic improvement in fatigue and leg ulcer pain. Within the following 2 months, he became pain-free and no longer required narcotics. By the end of the 9 months of therapy, the ulcers were completely healed (right) and quantitative IgM went down from 1058 to 325 mg/dL after the first 3 months. Nearly 2 years since starting the treatment, the patient is asymptomatic except for mild parasthesiae. He continues on Ibrutinib at a lower dose (280 mg daily). Cryoglobulinemia (CG) is a rare multisystem disorder which is caused by immunoglobulins with a capacity to aggregate at lower temperatures (cryoglobulins). Notably, even a small amount of cryoglobulin in the serum is sufficient to cause disease. Hence, a low-burden lymphoproliferative disorder that serves as the source of monoclonal cryoglobulin may be difficult to diagnose, precluding the use of targeted therapies. In agreement with a single prior report [1], our case shows that Ibrutinib can be remarkably effective in refractory CG due to WM. Unexpectedly, we found that despite a near-complete resolution of symptoms with Ibrutinib, the patient's cryoglobulins/IgM paraprotein persisted. In addition, the rheumatoid factor was still elevated, and C4 complement remained undetectable. This suggests that the therapeutic benefit of Ibrutinib may be explained not only by anti-tumor effect but also anti-inflammatory properties, as demonstrated by its efficacy in COVID [2], graft-versus-host disease [3], and autoimmune conditions [4]. Finally, our case shows that enriching for B-cells prior to molecular analysis may aid the diagnosis of occult lymphoproliferative disorder in other patients, for example those with IgM monoclonal gammopathy of clinical significance, who may also benefit from a trial of targeted therapy. H. Jamali wrote the manuscript. D. Wu performed cell sorting and molecular analysis. L. Soma performed morphological assessment of the bone marrow. M. Linenberger contributed to clinical management of the patient (plasma exchange). M. Wener provided rheumatology expertise and co-managed the patient with LS. L. Silberstein provided haematology expertise, co-managed the patient with MW, and wrote the manuscript. The authors have nothing to report. The authors received no specific funding for this work. None of the authors received financial compensation from an external source in return for writing or publishing this paper. The patient consented to the use of their clinical data and photographs for this correspondence.

Molecular Clusters and Tumor-Immune Drivers of IgM Monoclonal Gammopathies.

IgM monoclonal gammopathy of undetermined significance (MGUS) and Waldenström macroglobulinemia (WM) represent a disease spectrum with highly varied therapeutic management, ranging from observation to chemoimmunotherapy. The current classification relies solely on clinical features and does not explain the heterogeneity that exists within each of these conditions. Further investigation is warranted to shed light on the biology that may account for the clinical differences. We used bone marrow (BM) clonal CD19+ and/or CD138+ sorted cells, matched BM supernatant, and peripheral blood serum from 32 patients (7 MGUS, 25 WM) to perform the first multi-omics approach including whole-exome sequencing, RNA sequencing, proteomics, metabolomics, and mass cytometry. We identified three clusters with distinct pathway activation, immune content, metabolomic, and clinical features. Cluster 1 included only patients with WM and was characterized by transcriptional silencing of genes involved in cell cycle and immune response, enrichment of mitochondrial metabolism, infiltration of senescent T effector memory cells, and aggressive clinical behavior. Genetic/structural alterations of TNFAIP3 were distinct events of this cluster. Cluster 2 comprised both MGUS and WM patients with upregulation of inflammatory response, senescence and glycolysis signatures, increased activated T follicular helper and T regulatory cells, and indolent clinical behavior. Cluster 3 also included both MGUS and WM patients and exhibited intermediate features, including proliferative and inflammatory signaling, as well as glycolysis and mitochondrial metabolism. We have identified three distinct molecular clusters, suggesting a potential biologic classification that may have therapeutic implications.

Diagnostics in Waldenström’s macroglobulinemia: a consensus statement of the European Consortium for Waldenström’s Macroglobulinemia

The diagnosis of Waldenström’s macroglobulinemia (WM), an IgM-associated lymphoplasmacytic lymphoma, can be challenging due to the different forms of disease presentation. Furthermore, in recent years, WM has witnessed remarkable progress on the diagnostic front, as well as a deeper understanding of the disease biology, which has affected clinical practice. This, together with the increasing variety of tools and techniques available, makes it necessary to have a practical guidance for clinicians to perform the initial evaluation of patients with WM. In this paper, we present the consensus recommendations and laboratory requirements for the diagnosis of WM developed by the European Consortium of Waldenström’s Macroglobulinemia (ECWM), for both clinical practice as well as the research/academical setting. We provide the procedures for multiparametric flow cytometry, fluorescence in situ hybridization and molecular tests, and with this offer guidance for a standardized diagnostic work-up and methodological workflow of patients with IgM monoclonal gammopathy of uncertain significance, asymptomatic and symptomatic WM.

Second Primary Malignancy in Waldenström Macroglobulinemia: Insights from a Population-Based Analysis

INTRODUCTION: Waldenström Macroglobulinemia (WM), is a hyper-viscosity syndrome characterized by unrestricted proliferation of lymphoplasmacytic precursors in the bone marrow and monoclonal IgM gammopathy. The development of secondary primary malignancy (SPMs) in WM is a multifactorial phenomenon; the indolent nature of the disease, associated immune dysregulation, environmental factors and therapeutic measures, are responsible for high incidence of SPM in WM. This study was conducted to analyse the site-specific incidence of SPM in WM using data from the US Surveillance, Epidemiology and End Results (SEER) cancer registries. METHODS: A retrospective study was conducted using the SEER-18 dataset. WM patients who were diagnosed between 2000 and 2018, according to the ICD-O-3 = 9761/3 were included. Patients diagnosed on autopsy or through death certificates, and patients with incomplete follow-up data were excluded. SPM was defined as other malignancy appearing at least 1 year after WM diagnosis. Latency was defined as interval between WM and SPM diagnosis. Standardized incidence ratios (SIRs) and absolute excess risks (AERs) were calculated using SEER*Stat software (version 8.3.9). P-values and 95% confidence intervals (CI) were generated assuming Poisson distribution of observed incidence of SPM. RESULTS: A total of 4112 WM patients were identified. SPM was reported in 699 (17.0%) patients. The overall risk of developing SPM was significantly higher in WM patients as compared to the general population (SIR= 1.53, 95% CI=1.42-1.65, p <0.05) with an AER of 102.69 per 10,000 population. The risk of developing second primary solid tumors was significantly greater compared to the general population (SIR = 1.12, 95% CI= 1.02-1.23, p >0.05), but significantly increased risks were reported for secondary tumours of the lung and bronchus (SIR = 1.44), skin melanoma (SIR = 1.88), mouth (SIR 3.28), brain (SIR 2.73) and non-melanotic skin tumors (SIR = 4.09). The overall risk of developing secondary hematological malignancies was significantly increased (SIR = 4.95, 95% CI 4.31-5.66, p <0.05). Significantly increased risks were reported for nodal non-Hodgkin lymphoma (NHL) (SIR = 6.62), extranodal NHL (SIR = 11.3), acute lymphocytic leukemia (ALL) (SIR 8.04), acute non-lymphocytic leukemia (ANLL) (SIR = 4.2) and acute myeloid leukemia (AML) (SIR 4.22). Increased risk of SPMs was noted for patients with age 50-74 years (SIR= 1.65, 95%CI=1.44-1.89, p value <0.05) or > 75 years (SIR= 1.3, 95% CI= 1.13-1.49, p value <0.05), but not for patients younger than 50 years. Patients aged 50-74 years had a significantly increased risk of developing SPMs of lungs and bronchus (SIR 2.23), skin (SIR 3.09), vulva (SIR 8.5), thyroid (SIR 3.59), nodal NHL (SIR 6.06), extranodal NHL (SIR 11.87), ANLL (SIR 5.77) and AML (SIR 6.37). Patients aged >75 years had a significantly increased risk of developing SPMs of cecum (SIR 2.50), colon (SIR 1.62), soft tissues (SIR 5.25), nodal NHL (SIR 2.38), extranodal NHL (SIR 7.51), ANLL (SIR 3.69) and AML (SIR 3.63). Risk of SPM was significantly increased in both males (SIR 1.39) and females (SIR 1.59). On subsite evaluation, males had a significantly greater risk of SPMs involving lung and bronchus (SIR 1.71), soft tissues (SIR 4.52), skin (SIR 1.88), nodal NHL (SIR 3.85), extra-nodal NHL (SIR 6.9), ANLL (SIR 5.4) and AML (SIR 5.55). Females reported a significantly increased risk of SPM involving cecum (SIR 3.88), skin (SIR 2.87), vagina (SIR 11.51) nodal NHL (SIR 3.86) and extranodal NHL (SIR 13.57). The risk of SPM was significantly greater in Caucasians (SIR 1.46) but not African Americans or other races. The risk of SPM was significantly greater in patients at all latencies. The risk of SPM of cecum (SIR 2.76) and non-melanotic skin cancer (SIR 5.52) was significantly greater in patients with latency of 12-59 months, but not at subsequent latencies. The risk of melanotic skin cancer (SIR 2.61) was significantly greater in patients with latency of 60-119 months but not other latencies. The risk of thyroid cancer (SIR 6.43) was significantly increased for patients with latency 120+ months only. CONCLUSION: This study showed that 17% of WM patients developed SPM. WM patients were at a 53% greater risk of developing SPM compared to the general population. Caucasians and patients aged greater than 50 years were at particularly high risk of developing SPM. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Progression Risk and Long-Term Survival Trends of 915 Patients with Asymptomatic IgM Monoclonal Gammopathy

BACKGROUND: Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with a serum monoclonal IgM. Early asymptomatic stages include IgM monoclonal gammopathy of undetermined significance (MGUS) and smoldering WM (SWM). While most IgM MGUS patients (pts) will not progress during follow-up, a greater proportion of SWM pts will do. Most prognostic models identify high-risk SWM; however, they fail to characterize IgM MGUS and low-risk SWM. Moreover, data is scarce regarding how IgM MGUS and SWM survival trends have evolved during the last decades. We wondered whether inclusion of new biomarkers could improve progression risk models using the largest cohort of IgM MGUS and SWM reported. Here, we describe a comprehensive proposal to model progression risk and give more insight into the survival trends of IgM MGUS and SWM using retrospective data from 13 Spanish hospitals. METHODS: Diagnostic criteria were defined by the Second International Workshop. MYD88 L265P was analyzed by allele-specific or digital droplet polymerase chain reaction. Progression free survival (PFS) was calculated from the date of diagnosis to last follow-up or disease progression (symptomatic WM, other non-Hodgkin lymphoma or AL amyloidosis). Overall survival (OS) was calculated up to death from any cause. To find the best model, we first used a backward stepwise regression with meaningful variables as continuous. Also, a logistic and lasso regression (least shrinkage and selection operator) selected important variables that predicted progression at 10 years. We then categorized continuous data according to Liu and Youden methods. Relative survival (RS) was calculated using the Ederer II method leveraging the Human Mortality Database. RESULTS: 915 pts (462 IgM MGUS and 453 SWM) were included. Median age at diagnosis was 70 years. 102 (11%) pts were diagnosed before the year 2000. MYD88 L265P (available in 465 pts) was detected in 107 (54%) IgM MGUS and 217 (81%) SWM pts. After a median follow-up of 6 years, disease progression was documented in 250 pts (16% in IgM MGUS and 39% in SWM). The incidence rate of progression per 100 person-years was 2.9 (95% confidence interval [CI] 2.4 - 3.7) and 7.0 (95% CI 6.1 - 8.2) in IgM MGUS and SWM, respectively. Continuous (serum IgM, IgG, IgA, albumin, β2-microglobulin, bone marrow infiltration [BM]) and categorical (MYD88 L265P) candidates to clinical significance were fitted into a backward stepwise regression. Low IgG (hazard ratio [HR] 0.92; p=0.03), high IgM (HR 1.03; p<0.01), high BM infiltration (HR 1.02; p=0.01), and low albumin (HR 0.37; p<0.01) were selected. As the median follow-up of our series was 6 years, we also performed lasso to select predictors of progression at 10 years. Here, all previous variables were selected plus low IgA. We then chose the 4 best predictors between the two methods (BM infiltration, IgM, decreased IgG/IgA, and albumin). To fit into an easy-to-use model, we categorized continuous data as meaningful for clinicians. Albumin (<3.5 g/L) and IgG/IgA (<6.8/0.6 g/L) were categorized below the normal values; BM infiltration (≥ 20%) and IgM (≥ 10 g/L) cutpoints were established as previously described. 553 pts were introduced in the final model. Each variable was assigned a point so that low (0-1), intermediate (2) and high-risk (3-4) groups were able to discriminate pts. 84% of IgM MGUS pts were categorized as low-risk, while 57% of SWM were intermediate or high-risk. Regarding OS, there were no differences between IgM MGUS and SWM; however, each stage clearly differed from that of series of symptomatic WM pts from the same hospitals (p<0.01) (Figure 1A). Regarding survival trends, IgM MGUS had a RS slightly higher than that of the matched general population during the first 10 years of diagnosis, with a subsequent decline especially at 20 years. SWM had a RS lower than the general population, with a difference observed from the first 10-15 years of diagnosis (Figure 1B). CONCLUSION: We developed a new single ready-to-use risk model accounting for both IgM MGUS and SWM. Most IgM MGUS pts were categorized in the low-risk group, while SWM accounted for the vast majority of intermediate and high-risk groups. There were no differences in OS between IgM MGUS and SWM. However, RS of IgM MGUS was higher in the first 10 years from diagnosis, probably due to both early access to public health and follow-up, while SWM showed a constant decreasing RS. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Patients with IgM Monoclonal Gammopathy of Undetermined Significance (MGUS) or IgA with an M Band < 1.0 g/DL Have the Same Low Risk of Progression to Lymphoplasmacytic Neoplasm (LPN) As Those with IgG MGUS and an M-Band < 1.5 g/DL

Background Patients with MGUS can progress to LPN. Non-IgG subtype and the size of the M-band are known to correlate with the risk of progression. Consensus guidelines recommend that patients be monitored on an annual basis, but that IgG MGUS with an M-band < 1.5 g/dL, and a normal serum free light chain ratio is at low risk and can be managed with less intensive monitoring. There are limited data on the risk of progression to LPN in non-IgG MGUS with small M-bands. Methods Kaiser Permanente Northern California (KPNC) is a large integrated health care system serving more than 4 million members representative of Northern California residents. We identified a cohort of 3,303 KPNC health plan members who had at least one serum protein electrophoresis (SPEP) performed between January 1997 and December 2006 and extracted follow up data through December 2016. We excluded those with an M-Band > 3 g/dL, absence of a confirmatory immunofixation, or LPN before through 3 months after initial SPEP. The primary end point was progression to LPN, defined as multiple myeloma (MM), non-Hodgkin's lymphoma, or amyloidosis, and identified via an integrated tumor registry and, in the case of amyloidosis, by clinic diagnosis. Findings The median age of this cohort was 73 (IQR 63-80), 54.5% were male, and the ethnicity of this group was White 66.9%, Black 17.2%, Asian 6.7%, Hispanic 7.7%, and others 1.6%. Sixty six percent had an IgG gammopathy and 73% of gammopathies were < 1.0 g/dL. Overall, there were 2.1 (2.0-2.3) progressions per 100 patient years. The number of progressions per 100 patient years for an M-band < 1.0 g/dL, 1.0-1.5 g/dL, and 1.5-3.0 g/dL were 1.4 (1.2-1.6), 3.5(2.9-4.1), and 6.6 (5.5-7.7) respectively. As can be seen in the Figure, the cumulative risk of progression to LPN was clinically similar for patients with an IgG ≥ 1.5 g/dL and IgA ≥ 1.0 g/dL and considerably increased compared to those with an IgG gammopathy < 1.5 gm/dL, IgA gammopathy < 1.0 g/dL, or an IgM of any size. Discussion It has been estimated that there are several million individuals in the United States with MGUS. Following a patient with MGUS indefinitely is a financial burden and creates a substantial psychologic burden for the patient. Others have found that the effect of an MGUS diagnosis on quality of life is greater than a new diagnosis of symptomatic MM. Therefore, identifying additional categories of MGUS that could be assigned to a low-risk category could potentially diminish the burden and stress of ongoing monitoring. Limitations of our study are that, owing to the period from which our cohort was accrued, and the nature by which they were identified, free light chain levels were not obtained, bone marrow biopsies were done infrequently, and modern advanced imaging was not performed. In the modern era, many of our cohort would likely be identified with more advanced neoplasia such as smoldering or frank MM accounting for the higher rates of progression compared with other published reports. We found that during much of the period covered by our study, the clinical diagnosis of Waldenstrom's Macroglobulinemia was used in a non-discriminatory manner. We therefore limited our definition of progression only to those subjects developing frank malignancy that qualified for inclusion in our tumor registry rather than the less rigorously defined entity of "Waldenstrom's Macroglobulinemia.". This likely accounts for the lower risk of progression to LPN among our cohort with IgM gammopathy than has been described elsewhere. Conclusion Patients with either IgM MGUS of any size or IgA MGUS with an M-band < 1.0 g/dL have an equivalent clinical risk of progression as patients with an IgG MGUS < 1.0 g/dL and should potentially be assigned to a low-risk category to decrease the burden and stress of ongoing monitoring. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Single-Cell Transcriptome Analysis Reveals Stem Cell-like Subsets in the Progression of Waldenström's Macroglobulinemia

Waldenström's macroglobulinemia (WM) is an uncommon lymphoproliferative disorder characterized by monoclonal immunoglobulin M protein production and bone marrow infiltration by lymphoplasmacytoid cells. It remains an incurable disease. IgM monoclonal gammopathy of undetermined significance (MGUS) is the premalignant condition and is associated with the risk of developing WM. MYD88L265P is a recurrent mutation found in more than 90% of WM patients, and this genetic event is detectable in at least half of IgM MGUS patients. However, the precise cellular landscape and the mechanisms of progression from IgM MGUS to WM remain unclear. Single-cell RNA sequencing (scRNA-seq) provides us a powerful approach to explore tumor heterogeneity and identify rare malignant cells. Anti-CD38 monoclonal antibodies have been introduced into the therapeutic arsenal for plasma cell diseases. Therefore, we analyzed CD38+ immune microenvironment together with B cells and plasma cells to illustrate the first cellular landscape of IgM MGUS and WM in single cell resolution. We isolated bone marrow CD19+ and CD19-CD38+ cells from WM patients(n=3), IgM MGUS patients(n=3) and healthy donors(n=3) and employed the 10x Genomics platform to perform single-cell transcriptomic sequencing. After quality control, our dataset contained a total of 73024 cells. We used UMAP to visualize the cell superclusters and identified clusters including B cells, plasma cells, CD3+CD20+ (CD19+) cells, T cells and NK cells based on the expression of canonical lineage markers and cluster-specific markers. We found that healthy donors had the highest percentage of B cells (72.7% in healthy donors, 19.0% in IgM MGUS patients, 60.5% in WM patients; p<0.001) and that IgM MGUS and WM patients had more NK and T cells than healthy controls (0.06% and 17.7%, respectively, in healthy donors; 24.1% and 20.5% in IgM MGUS patients; 8.5% and 24.0% in WM patients; p<0.001). We also noticed that CD3+CD20+(CD19+) cells were present in both IgM MGUS and WM patients. First, we investigated the cell clusters correlated with WM pathology including B cells and plasma cells. We compared the B-cell gene expression profiles after removing the early B cells. Compared with those of IgM MGUS patients, mature B cells of WM patients showed upregulation of PIM1, DUSP22, HES1, NEAT1, RGS1, RGS16, and GADD45B. Light chain restriction and higher CNV levels were found in B cells of WM patients. SCENIC analysis showed that FOS, FOSB, EGR1 and JUNB were downregulated in B cells from WM and IgM MGUS patients. REL, a proto-oncogene promoting the survival and proliferation of B lymphocytes, was upregulated in B cells of WM patients, and IRF8 and ELF1 were upregulated in B cells of IgM MGUS patients. Nevertheless, plasma cells of WM patients, IgM MGUS patients and healthy donors were colocalized in one cluster, which might indicate their similar gene expression patterns. Next, we further determined the characteristics of B-cell subpopulation with aberrant T-cell antigen expression. Trajectory analysis revealed that CD3+CD20+(CD19+) cells and pro-B cells were located at the same end of the branched structure and were then directed toward mature B cell and plasma cell fates, respectively (Figure. 1A). This inferred developmental trajectory suggested that CD3+CD20+(CD19+) cells may be tumor stem cell-like subset. Using flow cytometry, we validated that CD3 was expressed in a fraction of CD19+ cells (mean: 3.69%, range: 0.28%-15.10%) of bone marrow samples from 8 WM patients. In addition, targeted gene sequencing was performed on CD3+CD19+ and CD3-CD19+ cells from 6 WM patients. MYD88 were proved to be the most frequently mutated gene in this cell subset. And we inferred that MYD88 mutation might be the early events in tumorigenesis by VAF analysis (Figure. 1B). Additional subclonal hits, such as CXCR4 and MAP2K1 mutations, could be acquired during tumor progression. In conclusion, our study provides comprehensive insights into mechanisms of progression from IgM MGUS to WM. We identified the rare CD19+ cell subpopulation with T-cell antigen expression in WM patients. It will be interesting to explore novel therapeutic strategies targeting rare potential cancer-initiating cells in future. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

VEGF and IL-6 As Markers of Severity and Response to Treatment in Waldenstrom Macroglobulinemia and IgM-Monoclonal Gammopathy of Undetermined Significance: A Monocentric Experience

Background: Angiogenesis plays an important role in the development and the maintenance of hematolymphoid malignancies. Serum levels of angiogenic cytokines, such as vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6), are known to be increased in patients with Waldenstrom Macroglobulinemia (WM) and IgM monoclonal gammopathy of undetermined significance (MGUS). Even if the role of IL-6 and VEGF as markers of disease status and severity has been recognized, only a limited number of studies have addressed the role of cytokines in WM and there is no proof about any correlation between their serum levels in WM and IgM-MGUS patients. Nevertheless, their dosage at various stages of the disease aims to understand if they have a comparable pattern, and therefore they could be used in clinical practice for disease monitoring. Aims: This study aims to find a correlation of serum levels of VEGF and IL-6 with the burden of disease in our patients with IgM-MGUS and WM and to evaluate a possible relationship between the two angiogenic cytokines, in an attempt to identify potential markers of severity. Methods: We performed a retrospective monocentric study of 18 patients (ten with WM and eight with IgM-MGUS) with a median age of 73 years (range: 52-90), whose 66% were male. Patients with WM were at different stages of disease (four were naive, four in remission, two relapsed/refractory). A total of 18 controls with a similar age and gender distribution were also tested. Controls were selected among patients with neuropathies in the absence of any hematological condition. We used the 1:1 ratio for the selection of controls: for every male or female WM patient, one control of the same gender and of similar age was included. In order to find a relationship of VEGF and IL-6 with a laboratory parameter, IgM levels dosage for each patient have been measured at the same time-point of the measurement of the cytokines. In all patients and controls, we evaluated serum levels of VEGF and IL-6 using Immunoassay panels (i.e., anti-IL-6 and anti-VEGF ELISA kit). Results: All patients showed elevated values of angiogenic cytokines when compared with controls (P value < 0.05). Both VEGF and IL-6 serum levels (median values: 623,5 pg/mL and 4,5 pg/mL, respectively; ranges: 113,4-1981 pg/mL and 0,3-21,9 pg/mL, respectively) showed a positive correlation with IgM serum levels (median value: 2055 mg/dL, range: 300-6123 pg/mL) (Fig. 1a and 1b). Furthermore, the relationship between IL-6 and VEGF was statistically significant and could be explained by a linear model (P value = 0,007) (Fig. 1c). No statistically significant differences were observed between the different phases of WM. Conclusions: Evidence from our sample shows that serum levels of angiogenic cytokines as VEGF and IL-6 have a comparable pattern with IgM levels. Therefore, it seems reasonable to suggest that they could be used in clinical practice as markers of severity of disease and response to treatment. Moreover, since the cytokines profiles are comparable, IL-6 can be used interchangeably with VEGF, allowing the monitoring of the disease with easily availability and unexpensive techniques. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Acquired Von Willebrand Disease Associated with Hematologic Malignancies: Case Series and Literature Review

Objective: To describe a single institution experience of AvWD of the spectrum of presentation in hematologic malignancies. Introduction: Acquired von Willebrand disease (AvWD) is a rare acquired bleeding disorder characterized by mucocutaneous bleeding and functional alterations in von Willebrand factor (vWF). AvWD can be caused by numerous conditions but we are going to focus on those associated with hematologic malignancies. The pathogenic mechanisms responsible for the vWF abnormalities can include abnormal clearance due to binding of paraproteins, inhibition of vWF, adsorption to the surface of platelets, proteolysis from increased fluid shear stress, and decreased synthesis. Methods: Clinical review of 4 cases of AvWD at a tertiary academic medical center from January 2016 to January 2022. Results: Case 1: 57-year-old female with history of chronic thrombocytosis of 1.6 million and was diagnosed with a JAK2 V617F mutation positive essential thrombocythemia and concurrent iron deficiency anemia. She was placed on low dose aspirin for thromboprophylaxis and presented with hematochezia with a drop in hemoglobin from 9.7g/dL to 4.3g/dL, platelets were 857k/uL. At that time her aPTT was mildly elevated at 37.0 (normal 36.5) This prompted testing for von Willebrand disease which showed low vWF activity 50% and vWF GP I binding activity 47% with normal vWF antigen activity 82% and factor VIII clotting activity of 100 IU/ml. Aspirin was held and hydroxyurea initiated at 1000mg daily with clinical response. Coagulation testing including aPTT and vWF antigen, Activity and multimers normalized after cytoreduction of her platelets with hydrea. Case 2: 75-year-old male with history of stroke on aspirin. We saw the patient for erythrocytosis and made the diagnosis of JAK 2 V617F mutation positive polycythemia rubra vera. Phlebotomy was initiated however, he presented with large ecchymoses at the venipuncture sites following phlebotomy. Testing showed quantitative vWF and factor VIII were normal, abnormal GPIbM: vWF ratio and loss of highest molecular weight multimers. He was maintained on hydroxyurea 1500mg daily for target hematocrit of 40 g/dL and low dose aspirin thromboprophylaxis without recurrent bleeding. Case 3: A 68-year-old female who we were following with a history of an IgM monoclonal gammopathy of undetermined significance (MGUS) reported mild ecchymosis on the extremities. Testing showed low factor VIII level of 34% and low vWF antigen and activity at 29% and 22%, and normal vWF multimers. She has been observed without any therapy given lack of clinically significant bleeding. Three years later, she has now developed of cytopenias and bone marrow biopsy showed 30 - 40% lymphoplasmacytic infiltrate consistent with progression to Waldenström Macroglobulinemia. Case 4 60 year-old-male with history of an IgG lambda MGUS who presented with new onset recurrent melena without a source of bleeding found on endoscopy. Testing showed decreased vWF antigen 30% and vWF activity 21%, normal factor VIII activity 69% and all multimers decreased consistent with AvWD from his known MGUS. His recurrent mucosal bleeding was managed with weekly Humate P. Revlimid 10mg per day was initiated for MGUS. Two months later, his indices improved with normalized VWF multimers and VWF antigen 70% and factor VIII activity 142%, and with now only mildly decreased VWF activity at 48%. Recurrent bleeding ceased. Conclusions: Patients with hematologic malignancies may present with mucocutaneous bleeding which may mimic congenital vWD however, AvWD should be considered in this population of patients. In addition, patients with AvWD can present with varying degrees of bleeding which might be mistaken for platelet dysfunction due to the underlying malignancies or the addition of aspirin or anticoagulation. One must maintain high clinical suspicion for AvWD with new onset bleeding in setting of known myeloproliferative or lymphoproliferative disorder. vWF antigen, activity, factor VIII activity and multimer testing should be obtained to secure the diagnosis. Treatment of the underlying disorder will result in clinical and laboratory improvement.

Genomic Pathways Differentiating IgM-MGUS from Waldenstrom Macroglobulinemia: The Integrated microRNA and Gene Expression Landscape

Introduction Waldenstrom Macroglobulinemia (WM) is a rare non-Hodgkin lymphoma that is preceded by an IgM monoclonal gammopathy of undetermined significance (IgM-MGUS), a premalignant, clinically asymptomatic disorder. The factors underlying this malignant transformation remain poorly understood, but the stepwise accumulation of genomic abnormalities has been identified as a potential mechanism. Non-coding aspects of the genome are increasingly recognized as drivers of disease pathogenesis but remain under-explored in this disease spectrum. Previously, we have shown that several oncogenes are in close genomic proximity to overexpressed long non-coding RNAs in WM compared to IgM-MGUS (Paludo et al. 2019). In this study, we aimed to identify the microRNAs (miR) and genomic pathways which may facilitate the IgM-MGUS to WM malignant progression. Methodology Sorted CD19+ and CD138+ B cells from prospectively collected bone marrow samples of patients with IgM-MGUS (n=7) and WM (n=25) underwent total RNA extraction and sequencing. Profiling of miRNAs was conducted, and selection of targets of interest was performed through identifying differentially expressed miRNA between IgM-MGUS and WM with a log2 fold change (FC)>0.5 or <-0.5 and false discovery rate (FDR) <0.05. Next, mRNA sequencing was conducted on the same patient samples, and differential expression was performed the same way as the miRNA data to identify mRNA candidates. Differentially expressed miRNA/mRNA pairs between WM and IgM-MGUS with correlated biological expression, i.e. either upregulated (up) miRNA experimentally predicted to regulate downregulated (down) mRNA or vice versa, were selected. The miRNA/mRNA pairs identified here were evaluated using Ingenuity Pathway Analysis (IPA) to discover dysregulated genomic pathways between IgM-MGUS and WM. Only pathways with an absolute activation Z-score of ≥2 were selected, and dysregulated miRNA and associated genes involved in altered pathways were identified. Results There were 34 miRNAs (16 up/18 down) found to be significantly differentially expressed between IgM-MGUS and WM (Figure). Among these, miR-4532, miR-192, miR-3195, miR-6761, miR-1295, and miR-3934 were found to have the highest FC between these two conditions. After correlation of miRNA/mRNA pairs, the most differentially regulated pathways with recognized oncological relations were identified, among which, the ID-1, IL-8 and STAT3 pathways were found to be downregulated in WM compared to IgM-MGUS, while the PTEN pathway was found to be upregulated. More broadly, the G protein-coupled receptor (GPCR), and the tumor microenvironment (TM) pathways were both found to be downregulated in WM compared to IgM-MGUS. Some of the main miRNAs driving multiple pathways with key associated genes included: miR-20 (GPCR, TM, IL8, ID1) through regulation of cyclin D1 (CCND1), matrix metalloproteinase-2 (MMP2), and leukemia inhibitory factor (LIF), miR-1260 (ID1, GPCR, STAT3, TM) through regulation of B-cell lymphoma 2 (BCL-2), chemokine receptor 6 (CCR6), and ETS proto-oncogene 1 (ETS1), and miR-1295 (IL8, TM, GPCR) through regulation of vascular cell adhesion molecule 1 (VCAM1), matrix metallopeptidase 19 (MMP19), and hydroxycarboxylic acid receptor 2 (HCAR2). Conclusion Our study is one of the first to identify the altered non-coded transcriptomics in WM and MGUS. We found several differentially expressed miRNAs with a known oncological role, such as miR-4532, miR-20 and miR-1260, highlighting the role of miRNAs as potentially important epigenetic regulators in these two diseases. The genomic pathways found to be potentially regulated by miRNA may underlie the transition between the premalignant to malignant disease of IgM-MGUS to WM. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Polyneuropathy Associated with IgM Monoclonal Gammopathy; Advances in Genetics and Treatment, Focusing on Anti-MAG Antibodies

With increasing age, the chances of developing either MGUS or polyneuropathy increase as well. In some cases, there is a causative relationship between the IgM M-protein and polyneuropathy. In approximately half of these cases, IgM targets the myelin-associated glycoprotein (MAG). This results in chronic polyneuropathy with slowly progressive, predominantly sensory neurological deficits and distally demyelinating features in nerve conduction studies. Despite the disease being chronic and developing slowly, it can cause considerable impairment. We reviewed English medical publications between 1980 and May 2022 on IgM gammopathy-associated polyneuropathy, with special attention to studies addressing the pathophysiology or treatment of anti-MAG polyneuropathy. Treatment options have been limited to a temporizing effect of intravenous immunoglobulins in some patients and a more sustained effect of rituximab but in only 30 to 55 percent of patients. An increase in our knowledge concerning genetic mutations, particularly the MYD88L265P mutation, led to the development of novel targeted treatment options such as BTK inhibitors. Similarly, due to the increasing knowledge of the pathophysiology of anti-MAG polyneuropathy, new treatment options are emerging. Since anti-MAG polyneuropathy is a rare disease with diverse symptomatology, large trials with good outcome measures are a challenge.

Clinicopathologic characteristics and prognostic analysis of monoclonal gammopathy of renal significance (MGRS) in patients with IgM monoclonal gammopathy: a case series

Monoclonal gammopathy has emerged as an important cause of renal injury. Since the clinicopathologic features related to monotypic monoclonal gammopathy of renal significance with IgM monoclonal gammopathy (IgM-MGRS) are poorly described and it is uncertain if intervention improves renal survival and mortality, we report a series of such patients, characterizing their clinicopathologic spectrum and outcomes. We retrospectively analyzed 38 patients referred to one medical center between 2009 and 2019 with detectable serum monoclonal IgM by immunofixation, performance of a bone marrow biopsy and kidney biopsy-proven MGRS. Of the 38 patients identified, about half patients were amyloidosis, followed by cryoglobulinemic glomerulonephritis. Patients were divided into two groups on the basis of their kidney pathology: amyloid and non-amyloid. Patients with non-amyloidosis were more likely to have renal dysfunction, hematuria, anemia and hypocomplementemia and κ light chain was predominant in this sub-group. Amyloid patients were more often treated with chemotherapy than the non-amyloid patients (P = 0.002). There were no significant differences between amyloid and non-amyloid patients in mortality (48% vs 29%, P = 0.467) and incidence of ESRD (19% vs 59%, P = 0.103). The incidence of ESRD was lower in patients treated with chemotherapy and/or ASCT, compared to those without chemotherapy (25% vs 57%, P = 0.049), and it was also lower in the hematologic responders than non-responders (10% vs 40%, P = 0.047). Our study confirmed a diverse variety of clinicopathological features and outcomes in patients with IgM-MGRS. Chemotherapy and/or ASCT and deep hematologic responses might improve renal prognosis.

Prognostic impact of MYD88 and CXCR4 mutations assessed by droplet digital polymerase chain reaction in IgM monoclonal gammopathy of undetermined significance and smouldering Waldenström macroglobulinaemia.

Waldenström macroglobulinaemia (WM) is characterized by recurrent somatic mutations in MYD88 and CXCR4 genes. However, limitations arise when analysing these mutations in IgM monoclonal gammopathy of undetermined significance (MGUS) or smouldering WM (SWM) given the lower tumour load. Here, we used droplet digital polymerase chain reaction (ddPCR) to analyse MYD88 L265P and CXCR4 S338* mutations (C1013G and C1013A) in unsorted bone marrow (BM) or cell-free DNA (cfDNA) samples from 101 IgM MGUS and 69 SWM patients. ddPCR was more sensitive to assess MYD88 L265P compared to allele-specific PCR, especially in IgM MGUS (64% vs 39%). MYD88 mutation burden correlated with other laboratory biomarkers, particularly BM infiltration (r=0.8; p < 0.001). CXCR4 C1013G was analysed in MYD88-mutated samples with available genomic DNA and was detected in 19/54 (35%) and 18/42 (43%) IgM MGUS and SWM cases respectively, also showing correlation with BM involvement (r=0.9; p < 0.001). ddPCR also detected 8 (38%) and 10 (63%) MYD88-mutated cfDNA samples in IgM MGUS and SWM respectively. Moreover, high BM mutation burden (≥8% MYD88 and ≥2% CXCR4) was associated with an increased risk of progression to symptomatic WM. We show the clinical applicability of ddPCR to assess MYD88 and CXCR4 in IgM MGUS and SWM and provide a molecular-based risk classification.

A Canadian Perspective on the Treatment of Waldenström Macroglobulinemia.

Waldenström macroglobulinemia (WM) is a slowly progressing B-cell non-Hodgkin lymphoma characterized by monoclonal IgM gammopathy in the blood and infiltration of the bone marrow by clonal lymphoplasmacytic cells. As an incurable disease, the goals for therapy for WM are to relieve symptoms, slow disease progression, prevent organ damage, and maintain quality of life. However, given the rarity of WM, clinical trials comparing treatments for WM are limited and there is no definitive standard of care. The selection of first-line WM therapy is thus based on patient factors, disease characteristics, and drug access, with bendamustine-rituximab and Bruton’s tyrosine kinase (BTK) inhibitor therapy considered preferred treatments. Other treatments such as proteasome inhibitor- or purine analogue-based therapy, alternative chemoimmunotherapy, and autologous stem cell transplantation are generally reserved for the relapsed setting but may be used in rare circumstances in earlier lines of therapy. This paper summarizes the efficacy and safety of these WM therapies and discusses considerations for treatment from a Canadian perspective.

Malignant Evolution of Schnitzler Syndrome to Waldenström Macroglobulinemia: a Case Report

Abstract Introduction: Schnitzler syndrome (SchS), first described in 1972, is a rare autoinflammatory condition characterized by chronic urticaria and monoclonal gammopathy of IgM or, exceptionally, IgG profile. Additional features include recurrent fever, evidence of abnormal bone remodeling, a neutrophilic dermal infiltrate on skin biopsy, leukocytosis or elevated C-reactive protein, according to the Strasbourg criteria. Case Presentation: We describe the case of a 56-year-old Caucasian male patient, who suffered from chronic urticaria, moderate-grade fever, severe generalized fatigue and arthralgias. After five years of chronic disease evolution, he was referred to the hematology department where he was found to have IgM kappa light chain monoclonal gammopathy. The constellation of symptoms, a negative rheumatologic workup, and the finding of IgM monoclonal gammopathy determined the diagnosis of Schnitzler syndrome. Bone marrow biopsy proved the association of Waldenström macroglobulinemia. Conclusion: The main goal of our case report was to highlight the clinical features and treatment, with emphasis on the hematological aspects, to provide a better understanding and to raise awareness of Schnitzler syndrome among healthcare professionals.

Acquired von Willebrand syndrome and lymphoid neoplasms: A review of malignancy management, and propositions of practical recommendations.

Acquired von Willebrand syndrome (AWS) is a rare and potentially life-threatening bleeding disorder. AWS is primarily associated with lymphocyte-related disorders (AWS-LRD), such as lymphoma and IgM monoclonal gammopathy of undetermined significance (MGUS), and plasmocyte-related disorders (AWS-PRD), such as non-IgM MGUS and myeloma. Symptomatic treatments are important to control and prevent bleeding, but AWS-LRD and AWS-PRD can only be cured by targeting the responsible clonal cell. No reviews exist on this specific subgroup of AWS. We performed a literature review to help manage these rare cases. Thirty-two AWS-PRD and 43 AWS-LRD cases with data on malignancy treatment were reported in 56 articles from the Medline database. LRDs were exclusively indolent and primarily associated with IgM monoclonal compounds. LRDs and PRDs may be treated because of severe bleeding symptoms, but severe VWF deficiency did not necessarily correlate with severe bleeding. Immunosuppressive drugs in AWS-PRD, including rituximab, provided an overall response rate of AWS (AWS-ORR) of 30% (3/10), including short responses. Anti-myeloma drugs provided an AWS-ORR of 71.4% (20/28), with long-lasting remissions. Bortezomib was the most commonly used drug and provided an AWS-ORR of 66.7% (6/9), including therapeutic associations with other anti-myeloma drugs. Autologous and allogeneic stem cell transplantation was performed in eight and two patients, respectively, and some details on the management of AWS during these procedures were provided. Rituximab in AWS-LRD provided an AWS-ORR of 60% (3/5), and a chemotherapy + rituximab regimen increased the AWS-ORR to above 50%. Bleeding syndrome in AWS-PRD and AWS-LRD generally improved prior to AWS biological improvement. Long term remission of AWS due to lymphoid neoplasms is attainable by treating the underlying clonal cell. Some data and recommendations are provided to help answer difficult questions, including treatment timing, choice of drug, and the timing of evaluations and treatment changes.

Detection and Characterization of Paraproteinemia in Canine Chronic B-cell Lymphocytic Leukemia Using Routine and Free Light Chain Immunofixation.

Hyperglobulinemia is reported in 26% of canine chronic B-cell lymphocytic leukemia (B-CLL) cases. However, few cases have been characterized by protein electrophoresis and immunofixation (IF), and the incidence of a monoclonal protein (M-protein) is unknown using these techniques. To characterize and determine the proportion of canine B-CLL cases with an M-protein using plasma protein electrophoresis (PPE), routine and free light chain (fLC) IF, and to assess if productive B-CLL cases express MUM1/IRF4 by cell tube block (CTB). PPE, routine (targeting IgG, IgA, IgM, IgG4, and light chain) and fLC IF were performed using 48 dog B-CLL plasma samples from patients diagnosed via peripheral blood flow cytometry. CTB was performed on a separate cohort of 15 patients. Hyperproteinemia (>7.5g/dL) was present in 17/48 cases (35%). An M-protein was detected in 32/48 cases (67%). Of these, 19/32 cases (59%) had only complete (monoclonal heavy and light chain) M-proteins detected, 10/32 cases (31%) had both complete and fLC M-proteins detected, and 3/32 cases (9%) had only an fLC M-protein detected. IgM was the most common clonal immunoglobulin isotype detected (23 cases). CD21+ cell counts were higher in cases with detectable M-protein. Plasma fLC IF suggested β-γ region interference, likely caused by clotting proteins. All B-CLL cases consistently expressed PAX5 and did not express MUM1/IRF4. Most B-CLL cases had an M-protein and were not hyperproteinemic. Most cases with paraproteins had a complete IgM monoclonal gammopathy; a subset had documented fLCs. The prognostic significance of heavy and fLC presence should be evaluated.

IgM monoclonal gammopathies of clinical significance: diagnosis and management.

IgM monoclonal gammopathy of undetermined significance is a pre-malignant condition for Waldenström macroglobulinemia and other B-cell malignancies, defined by asymptomatic circulating IgM monoclonal protein below 30 g/L with a lymphoplasmacytic bone marrow infiltration of less than 10%. A significant proportion, however, develop unique immunological and biochemical manifestations related to the monoclonal protein itself in the absence of overt malignancy and are termed IgM-related disorders or, more recently, monoclonal gammopathy of clinical significance. The indication for treatment in affected patients is dictated by the pathological characteristics of the circulating IgM rather than the tumor itself. The clinical workup and treatment options vary widely and differ from those for Waldenström macroglobulinemia. The aim of this review is to alert clinicians to IgM monoclonal gammopathy of clinical significance and to provide practical guidance on when to screen for these phenotypes. We discuss clinical characteristics, the underlying clonal profile, diagnostic workup and treatment considerations for five important subtypes: cold agglutinin disease, type I and II cryoglobulinemia, IgM-associated peripheral neuropathy, Schnitzler syndrome and IgM-associated AL amyloidosis. The inhibition of the pathogenic effects of the IgM has led to great success in cold agglutinin disease and Schnitzler syndrome, whereas the other treatments are centered on eradicating the underlying clone. Treatment approaches in cryoglobulinemia and IgM-associated peripheral neuropathy are the least well developed. A multidisciplinary approach is required, particularly for IgM-related neuropathies and Schnitzler syndrome. Future work exploring novel, clone-directed agents and pathogenic IgM-directed therapies is welcomed.