Autoantibody Activity in Waldenström's Macroglobulinemia

Waldenström macroglobulinemia presenting as bilateral bloody pleural effusion: A case report

RATIONALE

Pleural effusion, especially bilateral bloody pleural effusion, is a rare complication of Waldenström macroglobulinemia (WM). Pleural effusion in patients with WM has many causes, such as infection, tumor invasion of the pleura, and rupture of the thoracic duct or its branches. Patients with WM presenting to the respiratory department with chest tightness and shortness of breath need more differential diagnosis by respiratory physicians, which is helpful for effective treatment. Herein, we present a case of MV diagnosis in a patient with bilateral bloody pleural effusion.

PATIENT CONCERN

Our patient is a 59-year-old man with WM presenting as having bilateral bloody pleural effusion.

INTERVENTIONS

The patient was treated with pleural effusion drainage. After confirming the diagnosis, the patient was treated with rituximab, cyclophosphamide, and dexamethasone.

OUTCOMES

Following these treatments, the patient's symptoms improved, and ultrasound showed a decrease in pleural effusion.

LESSONS

Despite its favorable prognosis, the cause of pleural effusion in a patient with WM can be challenging to diagnose. The cause of pleural effusion should be considered a differential diagnosis when diagnosing patients diagnosed with WM.

An updated perspective on immunoglobulin replacement in chronic lymphocytic leukaemia in the era of targeted therapies

Chronic lymphocytic leukaemia (CLL) is a malignancy of clonally expanded antigen-switched, neoplastic, mature B cells. CLL is characterised by a variable degree of immunosuppression and secondary hypogammaglobulinemia. B-cell depleting therapies have historically been deployed with a proportion of patients becoming resistant to multiple lines of treatment with an associated worsening of immunosuppression and heightened infection risk. Advances in molecular diagnostics and the development of new therapies targeting Bruton's tyrosine kinase and B-cell lymphoma-2 have resulted in novel insights into the cellular mechanisms associated with an increased infection risk and T-cell escape from the complex tumour environment found in CLL. Generally, immunoglobulin replacement therapy with polyvalent human immunoglobulin G (IgG) is indicated in patients with recurrent severe bacterial infections and low IgG levels, but there is no consensus on the threshold IgG level for initiation of such therapy. A proportion of CLL patients have residual IgG production, with preserved quality of the immunoglobulin molecules, and therefore a definition of 'IgG quality' may allow for lower dosing or less frequent treatment with immunoglobulin therapy in such patients. Immunoglobulin therapy can restore innate immunity and in conjunction with CLL targeted therapies may allow T-cell antigen priming, restore T-cell function thereby providing an escape from tumour-associated autoimmunity and the development of an immune-mediated anti-tumour effect. This review aims to discuss the mechanisms by which CLL-targeted therapy may exert a synergistic therapeutic effect with immunoglobulin replacement therapy both in terms of reducing tumour bulk and restoration of immune function.

Detectable serum IgM monoclonal gammopathy in non-hepatitis-associated mixed cryoglobulinemic glomerulonephritis: A case report and literature review

Cryoglobulinemia is the presence of circulating cryoglobulin which can cause systemic vasculitis and glomerulonephritis. Monoclonal gammopathy of renal significance is strongly associated with type I cryoglobulinemia, but the role of detectable serum monoclonal gammopathy in mixed (type II) cryoglobulinemia is not clearly established. We report a case of a 71-year-old woman who presented with skin rash, leg edema, and azotemia. Investigations showed a positive result for rheumatoid factor, low complement C4 level, positive result for serum cryoglobulin, and positive M-spike on serum protein electrophoresis and IgM kappa monoclonal gammopathy on serum immunofixation. Kidney biopsy revealed membranoproliferative glomerulonephritis, polytypic IgM-dominant deposits in an immunofluorescence study, and microtubular substructures in an electron microscopic study. After an extensive workup, no evidence of myeloma or lymphoma was found. A diagnosis of monoclonal gammopathy of renal significance-associated mixed cryoglobulinemic glomerulonephritis was made. Due to the detectable IgM kappa monoclonal gammopathy in the patient's serum, clonal-directed therapy was administered. The patient had been in clinical remission after treatment with clone-directed therapy with cyclophosphamide and steroids. The literature review for cases of type II cryoglobulinemic glomerulonephritis that have detectable serum monoclonal gammopathy are summarized in this study.

Disease outcomes and biomarkers of progression in smouldering Waldenström macroglobulinaemia

Patients with asymptomatic/smouldering Waldenström macroglobulinaemia (SWM) have a variable risk of progression to active WM. Our study evaluated 143 patients with SWM consecutively seen between January 1996 and December 2013. With a median [95% confidence interval (CI)] follow-up of 9·5 [8·1-11·5] years, the cumulative rate of progression was 11% at 1 year, 38% at 3 years and 55% at 5 years. On multivariate analysis, haemoglobin (Hb) ≤123 g/l [risk ratio (RR) 2·08; P = 0·009] and β₂ -microglobulin (β₂ M) ≥2·7 µg/ml (RR 2·0; P = 0·01) were independent predictors of a shorter time-to-progression (TTP) to active WM. Patients with myeloid differentiation factor 88 wild type (MYD88^WT ) genotype (n = 11) demonstrated a trend toward shorter TTP [median (95% CI) 1·7 (0·7-8·7) vs. 4·7 (2·4-7·7) years for the MYD88^L265P cohort, n = 42; P = 0·11]. The presence of C-X-C chemokine receptor type 4 (CXCR4) mutation (n = 29) did not impact the TTP (median: 3 years for CXCR4^WT vs. 5·6 years for CXCR4^MUT , P = 0·34). The overall survival (OS) for patients with SWM (median: 18·1 years) was comparable to an age-, sex- and calendar year-matched USA population (median: 20·3 years, P = 0·502). In conclusion, Hb and β₂ M at diagnosis represent independent predictors of progression to active WM. Comparable survival of SWM and a matched USA population argues against pre-emptive intervention in this patient population.

Managing complications secondary to Waldenström's macroglobulinemia

Introduction: Waldenström's macroglobulinemia (WM) is a rare lymphoma characterized by the accumulation of IgM-secreting lymphoplasmacytic cells in the bone marrow and other organs. Clinical sequelae relate to direct tissue infiltration by malignant cells but also to the physicochemical and immunological properties of the monoclonal IgM, resulting in a variety of disease-related complications.Areas covered: This narrative review, following a thorough Pubmed search of pertinent published literature, discusses complications secondary to WM, related to direct tumor infiltration, monoclonal IgM circulation, and deposition, as well as other less common ones. The description and pathophysiology of these complications were described together with their specific management strategies and in the context of available treatment options for WM (anti-CD20 monoclonal antibody-based combinations, proteasome inhibitors, BTK inhibitors, and other emerging ones).Expert opinion: The availability of many novel, active and less toxic regimens for the treatment of WM allows the management of the disease with strategies that depend on clinical presentation and disease-related complications, age, toxicity considerations, and presence of comorbidities.

Waldenström macroglobulinemia: 2021 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, lymphadenopathy, and rarely hyperviscosity.

DIAGNOSIS

Presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis. The L265P mutation in MYD88 is detectable in more than 90% of patients and is found in the majority of IgM MGUS patients.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, β₂ microglobulin, LDH and monoclonal IgM concentrations are characteristics that are predictive of outcomes.

RISK-ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-monotherapy is inferior to regimens that combine it with bendamustine, an alkylating agent, a proteosome inhibitor, or ibrutinib. Purine nucleoside analogues are active but usage is declining in favor of less toxic alternatives. The preferred Mayo Clinic induction is rituximab and bendamustine.

MANAGEMENT OF REFRACTORY DISEASE

Bortezomib, fludarabine, thalidomide, everolimus, Bruton Tyrosine Kinase inhibitors, carfilzomib, lenalidomide, and bendamustine have all been shown to have activity in relapsed WM. Given WM's natural history, reduction of therapy toxicity is an important part of treatment selection.

Evidence of B Cell Clonality and Investigation Into Properties of the IgM in Patients With Schnitzler Syndrome

The Schnitzler Syndrome (SchS) is an acquired, autoinflammatory condition successfully treated with IL-1 inhibition. The two main defining features of this late-onset condition are neutrophilic urticarial dermatoses (NUD) and the presence of an IgM monoclonal component. While the former aspect has been extensively studied in this disease setting, the enigmatic paraproteinaemia and its potential consequential effects within SchS, has not previously been thoroughly addressed. Previous studies analyzing clonal B cell repertoires have largely focused on autoimmune disorders such as Systemic Lupus Erythematous (SLE) and hematological malignancies such as Chronic Lymphocytic Leukaemia (CLL), where B-cell clonality is central to disease pathology. The present study uses next-generation sequencing to provide detailed insight into aspects of B cell VDJ recombination and properties of the resulting immunoglobulin chains. An overview of IgH regional dynamics in 10 SchS patients, with a particular focus on CDR3 sequences and VDJ gene usage is reported, highlighting the presence of specific B cell expansions. Protein microarray detected a substantial proportion of autoreactive IgM to nuclear target proteins, though a single universal target was not identified. Together, these genetic and functional findings impart new understanding into this rare disorder.

Primera serie de casos reportada en Colombia de la enfermedad por aglutininas frías primaria y secundaria

Introducción: la enfermedad por aglutininas frías (EAF) es un trastorno hematológico primario o secundario, caracterizado por la anemia hemolítica autoinmune causada por los anticuerpos IgM a bajas temperaturas. Clínicamente, presenta parestesias y acrocianosis inducidos por frío y fiebre, aunque también puede ser asintomática y solo identificarse por alteraciones en el hemograma. Objetivo: describir las manifestaciones clínicas y de laboratorio, las causas primarias y secundarias de la EAF y compararlas con series de casos descritos en la literatura. Materiales y métodos: análisis retrospectivo de datos clínicos de pacientes del Hospital Universitario San Vicente Fundación de Medellín con resultados positivos para aglutininas frías. Dichos análisis se realizaron en el laboratorio de hematología de la Universidad de Antioquia, consideramos como positivo título ≥ 1: 64 o con la prueba de Coombs directa y positiva para anticuerpos fríos. Resultados: se incluyen los títulos de crioaglutininas de 23 casos con EAF: 6 formas primarias, 4 asociadas con los linfoma no Hodgkin (LNH), 8 secundarias a enfermedades infecciosas y autoinmunes y, 5 asociados con enfermedades misceláneas. Discusión y conclusiones: esta es la primera serie de casos en Colombia de EAF. La edad y género fueron similares a los datos reportados en la literatura. Observamos un mayor número de pacientes que presentaban anemia hemolítica y con síntomas asociados al frío. La relación hemoglobina hematocrito fue 1:2. Dentro de las causas secundarias destacamos las vasculitis, el lupus y la malaria. De las causas primarias las más frecuentes fueron los LNH, específicamente, el linfoplasmocítico. El tratamiento más utilizado para pacientes con EAF primaria incluyo rituximab.

Waldenström macroglobulinemia: 2019 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, lymphadenopathy, and rarely hyperviscosity.

DIAGNOSIS

Presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis. The L265P mutation in MYD88 is detectable in >90% of patients and is found in the majority of IgM monoclonal gammopathy of undetermined significance patients.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, β2 microglobulin, and monoclonal IgM concentrations are characteristics that are predictive of outcomes.

RISK-ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-monotherapy is inferior to regimens that combine it with bendamustine, an alkylating agent, a proteosome inhibitor, or ibrutinib. Purine nucleoside analogs are active but usage is declining for less toxic alternatives. The preferred Mayo Clinic induction is rituximab and bendamustine. Potential for stem cell transplantation should be considered in selected younger patients.

MANAGEMENT OF REFRACTORY DISEASE

Bortezomib, fludarabine, thalidomide, everolimus, ibrutinib, carfilzomib, lenalidomide, and bendamustine have all been shown to have activity in relapsed WM. Given WM's natural history, reduction of therapy toxicity is an important part of treatment selection.

Waldenström macroglobulinemia: 2017 update on diagnosis, risk stratification, and management

Disease Overview: Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, lymphadenopathy, and rarely hyperviscosity.

DIAGNOSIS

Presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis. The L265P mutation in MYD88 is detectable in more than 90% of patients. Risk Stratification: Age, hemoglobin level, platelet count, β₂ microglobulin, and monoclonal IgM concentrations are characteristics required for prognosis. Risk-Adapted Therapy: Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-based therapy is used in virtually all U.S. patients with WM and can be combined with bendamustine, an alkylating agent, or a proteosome inhibitor. Purine nucleoside analogues are widely used in Europe. The preferred Mayo Clinic nonstudy therapeutic induction is rituximab and bendamustine. Potential for stem cell transplantation should be considered in induction therapy selection. Management of Refractory Disease: Bortezomib, fludarabine, thalidomide, everolimus, ibrutinib, carfilzomib, lenalidomide, and bendamustine have all been shown to have activity in WM. Given WM's natural history, reduction of complications will be a priority for future treatment trials. Am. J. Hematol. 92:209-217, 2017. © 2016 Wiley Periodicals, Inc.

Cold agglutinin disease

Primary chronic cold agglutinin disease (CAD) is a well-defined clinicopathologic entity in which a specific, clonal lymphoproliferative B-cell bone marrow disorder results in autoimmune hemolytic anemia. The immune hemolysis is entirely complement-dependent, predominantly mediated by activation of the classical pathway and phagocytosis of erythrocytes opsonized with complement protein C3b. Typical clinical features in CAD have diagnostic and therapeutic implications. Pharmacologic treatment should be offered to patients with symptom-producing anemia or disabling circulatory symptoms. CAD should not be treated with corticosteroids. Based on an individualized approach, rituximab monotherapy or rituximab-fludarabine in combination is recommended as first-line therapy. Rituximab-bendamustine is still an investigational therapy. Although complement-modulating agents are still to be considered experimental in CAD, therapy with the anti-C1s monoclonal antibody TNT009 seems promising.

Waldenström macroglobulinemia: 2015 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, lymphadenopathy, and rarely hyperviscosity.

DIAGNOSIS

Presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis. The L265P mutation in MYD88 is detectable in more than 90% of patients.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, β2 microglobulin, and monoclonal IgM concentrations are characteristics required for prognosis.

RISK-ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-based therapy is used in virtually all US patients with WM and can be combined with alkylating agent or purine nucleoside analog (or both). The preferred Mayo Clinic nonstudy therapeutic induction is rituximab, cyclophosphamide, and dexamethasone. Future stem cell transplantation should be considered in induction therapy selection. Management of Refractory Disease: Bortezomib, thalidomide, everolimus, ibrutinib, carfilzomib, lenalidomide, and bendamustine have all been shown to have activity in WM. Given WM's natural history, reduction of complications will be a priority for future treatment trials.

TNT003, an inhibitor of the serine protease C1s, prevents complement activation induced by cold agglutinins

Cold agglutinin–driven classical pathway activity terminates prior to the initiation of the terminal cascade in CAD patient blood. By inhibiting cold agglutinin–mediated complement deposition on the cellular membrane, TNT003 prevents RBCs from being phagocytosed.

Waldenström macroglobulinemia: 2013 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, and lymphadenopathy.

DIAGNOSIS

The presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, β2 microglobulin, and monoclonal IgM concentrations are characteristics required for prognosis.

RISK-ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-based therapy is used in virtually all US patients with WM and can be combined with alkylating agent or purine nucleoside analog (or both). The preferred Mayo Clinic nonstudy therapeutic induction is rituximab, cyclophosphamide, and dexamethasone. Future stem cell transplantation should be considered in induction therapy selection.

MANAGEMENT OF REFRACTORY DISEASE

Bortezomib, thalidomide, everolimus, lenalidomide, and bendamustine have all been shown to have activity in WM. Given WM's natural history, reduction of complications will be a priority for future treatment trials.

Waldenström macroglobulinemia: 2012 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, and lymphadenopathy.

DIAGNOSIS

Presence of IgM monoclonal protein associated with ≥10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, β(2) microglobulin, and monoclonal IgM concentrations are characteristics required for prognosis.

RISK-ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-based therapy is used in virtually all US patients with WM and can be combined with alkylating agent or purine nucleoside analog (or both). The preferred Mayo Clinic nonstudy therapeutic induction is rituximab, cyclophosphamide, and dexamethasone. Future stem-cell transplantation should be considered in induction therapy selection.

MANAGEMENT OF REFRACTORY DISEASE

Bortezomib, thalidomide, lenalidomide, and bendamustine have all been shown to have activity in WM. Given WM's natural history, reduction of complications will be a priority for future treatment trials.

Waldenström macroglobulinemia: 2011 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma with immunoglobulin M (IgM) monoclonal protein. Clinical features include anemia, thrombocytopenia, hepatosplenomegaly, and lymphadenopathy.

DIAGNOSIS

Presence of IgM monoclonal protein associated with 10% clonal lymphoplasmacytic cells in bone marrow confirms the diagnosis.

RISK STRATIFICATION

Age, hemoglobin level, platelet count, b2-microglobulin, and monoclonal IgM concentrations are characteristics required for prognosis.

RISK ADAPTED THERAPY

Not all patients who fulfill WM criteria require therapy; these patients can be observed until symptoms develop. Rituximab-based therapy is used in virtually all US patients with WM and can be combined with alkylating agent or purine nucleoside analogue, or both. The preferred Mayo Clinic nonstudy therapeutic induction is rituximab, cyclophosphamide, and dexamethasone. Future stem cell transplantation should be considered in induction therapy selection.

MANAGEMENT OF REFRACTORY DISEASE

Bortezomib, thalidomide, lenalidomide, and bendamustine have all been shown to have activity in WM. Given WM’s natural history, reduction of complications will be a priority for future treatment trials.

Heating up cold agglutinins

In this issue of Blood, Berentsen and coworkers describe a high response rate which is durable in some patients who receive combination fludarabine and rituximab for chronic cold agglutinin disease (CAD). If confirmed, this is a significant advance in therapy for a frequently difficult clinical problem.

Immune thrombocytopenia in lymphoproliferative disorders

Lymphoproliferative disorders are recognized as a common cause of secondary immune thrombocytopenia (ITP). The mechanisms involved in the pathogenesis of ITP associated with lymphoproliferative disorders are heterogeneous and often linked to the presence and activity of the malignant clone. A better understanding of the responsible mechanisms leading to ITP in each disease may allow for targeted treatment decisions, avoiding unwarranted immunosuppression and bleeding complications.

Autoantibodies in patients with monoclonal gammopathies

Although autoantibody activities are rather often associated to monoclonal gammopathies, only monoclonal immunoglobulins of the IgM isotype are really directed against autoantigens that are often polysaccharides or are formed by highly repetitive structures. This strict association is frequently revealed also by clinical manifestations of the autoimmune response generated by the monoclonal macroglobulin. Most monoclonal immunoglobulins of non-IgM isotype are instead totally inactive toward self-antigens, the autoantibody activity being instead associated, if present, to polyclonal immunoglobulins. Although the same BAFF/APRIL system is involved in perpetuation of humoral autoimmunity as well as in stimulation of clonal B-cell expansion, the autoimmune commitment of B cells of a non-IgM isotype is hardly compatible with their possible involvement in an uncontrolled proliferation pathway, whose prerequisite is the homing of these B cells to the bone marrow compartment. The IgM-secreting cells appear instead to possess a much lower tendency, and/or a looser requirement, for their homing in the bone marrow prior to their actual proliferation. This may explain the quite different consequences, in terms of autoimmunity, between IgM and non-IgM paraproteinemias.

Acquired deficiency of the inhibitor of the first complement component: presentation, diagnosis, course, and conventional management

Acquired deficiency of the inhibitor of the first complement component (C1-INH) is a rare, potentially life-threatening disease whose cause, course, and management are not completely defined. This article analyzes the etiopathogenetic mechanism, the clinical presentation, and the relationship between acquired C1-INH deficiency and lymphoproliferative disorders. Moreover, the authors give an overview of the outcome of the disease and the different therapies proposed to cure it.

Adaptation of humoral memory

Immunological memory, as provided by antibodies, depends on the continued presence of antibody-secreting cells, such as long-lived plasma cells of the bone marrow. Survival niches for these memory plasma cells are limited in number. In an established immune system, acquisition of new plasma cells, generated in response to recent pathogenic challenges, requires elimination of old memory plasma cells. Here, we review the adaptation of plasma cell memory to new pathogens. This adaptation is dependent upon the influx of plasmablasts, generated in a secondary systemic immune reaction, into the pool of memory plasma cells, the efficiency of competition of new plasmablasts with old plasma cells, and the frequency of infection with novel pathogens. To maintain old plasma cells at frequencies high enough to provide protection and to accommodate as many specificities as possible, an optimal influx rate per infection exists. This optimal rate is approximately three times higher than the minimal number of plasma cells providing protection. Influx rates of plasmablasts generated by vaccination approximately match this optimum level. Furthermore, the observed stability of serum concentrations of vaccine-specific antibodies implies that the influxing plasmablasts mobilize a similar number of plasma cells and that competitive infectious challenges are not more frequent than once per month.

Dangerous small B-cell clones

The detection of a monoclonal immunoglobulin in serum or urine usually raises concerns about the size of the underlying B-cell-derived clone and possible systemic effects caused by its expansion. However, a small clone can synthesize a very toxic protein, producing devastating systemic damage and protean clinical presentations. The resulting "monoclonal component-related diseases," although difficult to diagnose, may be progressive and even fatal. The monoclonal protein can aggregate and deposit systemically as occurs in light-chain amyloidosis, monoclonal immunoglobulin deposition disease, crystal-storing histiocytosis, and monoclonal cryoglobulinemia. Alternatively, some monoclonal proteins possess antibody activity toward autogenous antigens and cause chronic cold agglutinin disease, mixed cryoglobulinemia, and peripheral neuropathies. Other humoral mediators may contribute to neuropathy in variant disorders such as the POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) syndrome. The clone synthesizing the noxious monoclonal proteins is often small, and sensitive techniques may be required to detect these immunoglobulins. A delay in diagnosis can allow irreversible organ damage and dramatically shorten survival. Prompt recognition of suggestive signs and symptoms should trigger a thorough diagnostic approach to reach the correct diagnosis quickly, because this is the key to effective therapy. Although the treatment of these conditions is not optimal, significant advances have been made, improving the duration and quality of life.