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Human hybridomas that secrete monoclonal IgM anti-myelin-associated glycoprotein antibodies were generated by fusion with cells from a patient with peripheral neuropathy and IgM monoclonal gammopathy. Karyotypic analysis of the hybridoma cells revealed no chromosomal abnormalities. The cells were positive for cell-surface idiotype HLA-DR and the plasma cell antigen PCA-1, and negative for the B-cell determinant B4 and for Leu-1, which has been postulated to distinguish a subpopulation of B cells that secrete IgM with autoantibody activity.

Two Japanese patients with Sjögren's syndrome with non-immunoglobulin M(IgM) class monoclonal gammopathy are described. The monoclonal IgA lambda detected in the serum and saliva was confirmed to possess rheumatoid factor activity in the first patient with a hypergammaglobulinemic purpura and hyperviscosity syndrome. Idiotype specificity was present on the surface membrane of peripheral blood lymphocytes as well as in the cytoplasm of infiltrating cells in the salivary glands. Common idiotypic specificity was found in four of 60 other patients who had rheumatoid factors. In the serum and saliva of the other patient, a monoclonal immunoglobulin G, kappa type (IgG kappa), was detected. Kappa type IgG was found in most of the infiltrating cells in the salivary glands and also in the saline extract from a resected submandibular gland. Our findings indicate that non-IgM class monoclonal gammopathy is also one of the complications of Sjögren's syndrome.

Nerve biopsy in peripheral neuropathies associated with an IgM monoclonal gammopathy may occasionally display focal myelin thickenings. In a patient with such an IgM neuropathy, in whom an anti-myelin-associated glycoprotein (MAG) antibody activity was present in the serum, single-fiber preparations revealed 34% of internodes bearing myelin swellings. The morphometric, morphological and ultrastructural findings were reminiscent but not identical to those of the hereditary tomaculous neuropathy with liability to pressure palsies. Atypical features for tomacula included lack of spiralization of the redundant loops of myelin around the axons and their predominant external situation with regard to the myelin sheath. The frequent colocalization of myelin thickenings and the widening of myelin lamellae typical of IgM neuropathies, are highly suggestive of some pathogenetic link between the two abnormalities. The redundant loops of myelin in IgM neuropathies possibly result from a defect in the axon-myelin adhesion secondary to the binding of IgM on an epitope of MAG directly involved in cell-cell adhesion.

The characteristics of T and B lymphocyte profile and B lymphocyte specificity repertoire were compared in patients with Waldenstrom's macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (IgM MGUS), multiple myeloma (MM), and age-matched normal subjects. Patients with MM had both significantly reduced frequency and number of sIg+ (surface Ig) B cells, whereas patients with WM and IgM MGUS had a reduced frequency but normal numbers of sIg+ B cells in circulation as detected in a capping assay. WM was distinguished by the large numbers of cells in the peripheral blood lymphocyte (PBL) pool that expressed CD9 (BA-2) and CD24 (BA-1) and were monoclonal, based on light chain analysis using flow cytometry. The profile of T lineage cells showed that the ratio of CD4:CD8 was significantly reduced in both MM and WM due to a reduction in the CD4 set. The CD4+ cells were qualitatively abnormal as well, with an enriched proportion of the 4B4+ (CDw29) subset and decreased proportion of the Lp220+ (CD45R) subset. This appeared to be an effect of the disease process on the relatively immature Lp220+ set. From clonal analysis, those patients with WM or IgM MGUS (unlike MM patients) did not exhibit enhanced reactivity with auto-Ig determinants, and most WM patients (7/8) and half of the IgM MGUS patients (3/6) did not have enriched proportions of B cells reactive to tetanus toxoid (TT). The TT-specific B cells in both WM and IgM MGUS, in contrast to MM, appeared fully functional in secretion of anti-TT IgM in vivo. We speculate that the more severe immunodeficiency in MM may be controlled or exacerbated by the presence of an anti-Ig network. The absence of this network in WM allows a relatively more effective immune response, but the immunodeficiency that is observed in these patients involves some abnormality in normal lymphocyte differentiation (is also present in MM).

Quantitative, immunopathological, light and electron microscopic studies of superficial peroneal nerve biopsies from 31 patients with IgM monoclonal gammopathy were carried out. Six patients had Waldenström's macroglobulinemia and 25 had IgM monoclonal gammopathy of undetermined significance. Serum samples from 28 of these patients were assayed for anti-myelin-associated glycoprotein (anti-MAG) activity. Anti-MAG activity was found in 25 of the samples. There was a relationship between the widening of some myelin lamellae observed on ultrastructural examination and the serum anti-MAG activity (23 cases). Immunopathological examination showed IgM binding to myelin sheaths in 17 cases.

A 19-month-old cat investigated because of depression, anorexia, polyuria, and polydipsia was found to have hepatomegaly, retinal haemorrhages, and distended tortuous retinal veins. Prolonged bleeding occurred after venipuncture, and serum was hyperviscous due to an immunoglobulin M monoclonal gammopathy. Prothrombin and activated partial thromboplastin times were prolonged, thrombin clotting time was only slightly prolonged and the activities of coagulation factors VII, VIII and IX were normal. The cat died suddenly before the origin of the immunoglobulin could be determined. Hepatic plasmacytoid lymphosarcoma was found at post-mortem examination. The pathophysiology of hyperviscosity syndrome is discussed and the observations in this cat are compared with those reported in the dog.

Essential mixed cryoglobulinemia, which can cause hypersensitivity vasculitis, was observed in five patients with peripheral neuropathy. Three cases presented with multifocal neuropathies and two cases with symmetrical polyneuropathy. One had cryoglobulinemia with IgM monoclonal gammopathy and IgG polyclonal gammopathy, and the other four had cryoglobulinemia with polyclonal gammopathy. Biopsies showed perivascular infiltration by mononuclaer cells around medium, and mainly small-sized blood vessels. This was observed in the epineurium (five cases) and muscular fragments (three cases). At ultrastructural examination two cases showed severe damage of most myelinated fibers, which presented acute stages of Wallerian-like degeneration, and the three other cases showed a less widespread destruction of myelinated fibers. Most endoneurial capillaries showed swollen endoneurial cells. Myelino-axonal degeneration of myelinated fibers is probably due mainly to the vasculitis always present in the epineurium. This damage was probably worsened by the modifications of endoneurial capillaries. These lesions and their mechanisms are quite different from those observed in cases of cryoglobulinemia with an isolated monoclonal gammopathy.

A 54-year-old male had monoclonal IgM-kappa light chains in the serum and free monoclonal kappa light chains in the urine. Renal biopsy revealed nodular glomerulosclerosis associated with the accumulation of kappa light chains. Isolated microscopic hematuria was present for over 1 year. He also showed a defect in urine concentration for which the light chains deposited along the basement membrane in the inner medullary tubules were judged to be responsible. When the glomerular filtration rate fell to 30 ml/min, the syndrome of mild renal failure, decreased potassium excretion, and hyporeninemic hypoaldosteronism developed, suggesting that kappa light chain nephropathy is a cause of this syndrome. Chemotherapy appeared to have some beneficial effects in maintaining renal function.

In 15 patients with lymphoproliferative diseases of various types, histologic studies suggested monoclonal gammopathy. This was confirmed immunoelectrophoretically in the serum, urine, or both, from 10 patients. Seven of these 10 patients had IgM (kappa), one had IgM (lambda), one had IgA (kappa), and one had Bence Jones (lambda). Of the other five patients, three had polyclonal IgM elevations and two had no detectable monoclonal or polyclonal immunoglobulin abnormalities. Nuclear periodic acid-Schiff positive globules, heretofore considered to be characteristic of macroglobulinemia of Waldenstrom, were found in only three patients with IgM monoclonal gammopathy. In two of these, the globules were found only after a prolonged search. They were also seen in one patient with IgA monoclonal gammopathy. They were abundant in one of three patients with polyclonal IgM gammopathy. A high frequency of nuclear PAS positive globules was also observed in three additional patients. One of these patients had an unclassifiable malignant lymphoma involving a submandibular lymph node, and the other two had lymphoid hyperplasias involving the skin and nasopharynx, respectively. Nuclear periodic acid-Schiff positive globules were more abundant and more consistently present in our cases of polyclonal IgM gammopathy than in cases with monoclonal IgM gammopathy, regardless of the neoplastic or non-neoplastic nature of the immunoglobulin-producing lesions.

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 Waldenstrom'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.

Some cases of peripheral neuropathy associated with benign IgM monoclonal gammopathy, or Waldenstrom's macroglobulinemia, are probably of autoimmune origin; in some cases, anti-IgM serum reacts with the myelin sheaths of peripheral nerves. However, mechanisms may differ in other cases. In one case of neuropathy with macroglobulinemia, we found deposits of IgM immunoglobulin in the endoneurium. On ultrastructural examination, the deposits had erased the basement membrane of some nerve fibers that showed damage of both myelin and axon.

Twenty-seven patients with neuropathy and IgM monoclonal gammopathy were tested for antigen specificity of the M-protein and for anti-myelin-associated glycoprotein (MAG) IgM levels by immunoblot. In 16 patients (59.2%) the M-protein reacted with MAG and with cross-reactive glycoconjugates. Anti-MAG IgM titers in these patients ranged between 1:12,800 and 1:100,000. A fainter IgM reactivity with MAG and related glycoconjugates was detected in 3 additional patients with neuropathy, but also in 8 of 24 patients with IgM M-protein without neuropathy (33.3%). This reactivity was not due to the M-protein and corresponded to antibody titers of 1:400 or less in all but 1 patient with a titer of 1:3,200. Low titers of anti-MAG IgM (1:200 or less) were also detected in 17 of 101 control patients without IgM M-proteins (16.8%), while 1 patient with neuropathy of unknown cause had anti-MAG IgMK titers of 1:25,600. In 1 patient with neuropathy and IgM M-protein that was not anti-MAG, the M-protein bound to other antigens in nerve, while in 6, other possible causes or mechanisms for the neuropathy were found. In this study, high titers of anti-MAG IgM antibodies were always associated with neuropathy. The presence of low levels of anti-MAG IgM in a significant proportion of controls suggests that monoclonal expansion of naturally occurring B-cell clones secreting anti-MAG IgM may be responsible for the high incidence of this antigen specificity of the M-protein.

A patient with acute leukemia and an IgM, kappa (IgMkappa) monoclonal gammopathy, Bence-Jones proteinuria, and blasts containing intracytoplasmic vacuoles with peroxidase-positive inclusions is discussed. Special stains, immunofluorescence, and electron microscopy suggested that the vacuoles were autophagosomes containing Auer-body-like inclusions, and that the blast cells did not synthesize the paraprotein. Chemotherapy with cyclophosphamide, vincristine, and prednisone resulted in transient improvement of the leukemia, but the level of the paraprotein was unchanged. Other case reports involving monoclonal gammopathy in association with acute leukemia are reviewed and contrasted with this case.

A sister and a brother with a progressive mixed axonal and demyelinating polyneuropathy were found to have a monoclonal IgM gammopathy of kappa and lambda type, respectively. Sural nerve and cutaneous nerve specimens obtained by biopsy showed deposits of IgM on myelin sheets. Sera from both patients contained antibodies directed to bovine peripheral nerve myelin as determined by ELISA technique and to normal human peripheral nerve myelin as demonstrated by indirect immunofluorescence histochemistry. These siblings may have a genetic predisposition to the formation of autoantibodies with peripheral nerve myelin as the target for the immune attack.

An immunological mechanism may be responsible for the peripheral neuropathies associated with the IgM monoclonal gammopathies. Myelin-associated glycoprotein, and sulfated glucuronic acid-glycosphingolipids of the paragloboside type specific of peripheral nervous system (PNS), have been found to be targets for these antibodies. We report here on the presence of a glycolipid antigen present in central nervous system white matter in 7 of 12 patients with IgM monoclonal gammopathy and neuropathy whose IgM reacts also with the specific sulfated glycolipids of PNS. Immunodetection of the antibodies was performed on thin-layer plates after separation of the glycosphingolipids from peripheral nerve and white matter. The lipid antigen had a migration on thin-layer chromatography close to sulfogalactosylceramide but the sulfatide standard did not react with the monoclonal IgM.

Attention has recently been directed toward patients having a polyneuropathy and a monoclonal IgM anti-myelin-associated glycoprotein (anti-MAG) antibody. The possibility of a pathogenetic role for the anti-MAG antibody in the evolution of the polyneuropathy and in the development of central nervous system signs, including tremor and ataxia, remains unresolved. In 5 patients with this syndrome whose clinical courses were followed closely, in 1 of whom a complete postmortem examination of the nervous system was performed, we made the following observations: the anti-MAG antibody did not localize to the compact layer of the myelin sheath in affected nerves, but did localize to areas of myelin splitting; anti-MAG antibody present in the sural nerve of an affected individual for 7 years was not associated with progressive pathology; anti-MAG antibody was not deposited in the central nervous system of an affected individual, although the antibody did bind to these same tissues in vitro; deposition of anti-MAG antibody observed at postmortem examination did not correlate with the degree of pathological change; and study of the peripheral nervous system favored a primary axonal neuropathy with secondary demyelination.

IgM monoclonal gammopathy has been reported in some patients with motor neuron disease. The monoclonal IgMs in several of the patients bind to the carbohydrate epitope Gal (beta 1-3) GalNAc, which is shared by gangliosides GM1 and GD1b and glycoproteins in the nervous system and crossreacted with Gal (beta 1-3) GlcNAc. They also immunostain spinal cord and gray matter and presynaptic terminals of motor neurons at the neuromuscular junction. The role and mechanisms of action of these antibodies in motor neuron disease is under investigation.

It has been postulated that binding of monoclonal IgM from the sera of some patients with IgM monoclonal gammopathy and neuropathy to components of peripheral nerve may play a key role in the pathogenesis of the neuropathy. Serum IgM from these patients has been shown to bind to antigenic determinants shared by the myelin-associated glycoprotein (MAG) and a polar glycolipid from peripheral nerve. Here we describe a study of sera from eight patients with IgM monoclonal gammopathy and neuropathy. Five of the patients had serum IgM directed both against MAG and one or two polar glycolipids from peripheral nerve. One of the patients had serum IgM that bound to a peripheral nerve glycolipid but not to MAG; no one had serum IgM that bound to MAG but not to a peripheral nerve glycolipid. The relative affinity of IgM from the sera of the patients for proteins in peripheral nerves of chickens, dogs, and humans varied from patient to patient. These data indicate that the epitope against which the serum IgM from these patients is directed is not necessarily the same in all of the cases.

A case of an IgM monoclonal gammopathy associated with oral lesions of lupus erythematosus is described and the possible interrelationship of the lesions discussed.

We investigated the epitope specificity of monoclonal antibodies (M-proteins) from two patients with motor neuron disease and IgM monoclonal gammopathy. In previous studies, both M-proteins bound to gangliosides GM1 and GD1b which share Gal(beta 1-3)GalNAc as their terminal structure, and to lacto-N-tetraose-BSA which has the structure Gal(beta 1-3)GlcNAc(beta 1-3)Gal(beta 1-4)Glc-BSA. In this study we show that the serum IgM from both patients bind to bovine serum albumin (BSA) glycoconjugates of both Gal(beta 1-3)GalNAc and Gal(beta 1-3)GlcNAc. Binding was detected at serum dilutions of up to 1:100,000, and absorption with Gal(beta 1-3)GlcNAc-BSA completely removed the IgM binding to Gal(beta 1-3)-GalNAc-BSA, indicating that the same antibodies bound to both epitopes. Low levels of antibodies to Gal(beta 1-3)GlcNAc-BSA and to Gal(beta 1-3)GlcNAc-BSA were also detected in patients with amyotrophic lateral sclerosis (ALS) and in normal subjects at serum dilutions of up to 1:500, but these did not have the same specificity as the M-proteins, as binding to Gal(beta 1-3)GalNAc-BSA was not inhibited by absorption with Gal(beta 1-3)GlcNAc-BSA.

In eight of 10 consecutive cases of IgM monoclonal gammopathy of undetermined significance (MGUS), the M-protein had specificity towards various tissues as estimated by direct and indirect immunofluorescence studies of skin and/or sural nerve biopsies. Five of the cases had neuropathy. In three of them, including two siblings with a demyelinating peripheral neuropathy, the IgM was bound to the myelin-associated glycoprotein (MAG) of peripheral nerves. One had axonal neuropathy with IgM activity against the peri- and endoneurium, while another case with post-infectious neuritis had IgM activity against structures in the endoneurium but no IgM autoimmunity in the direct fluorescence test. The latter improved clinically in parallel with a decrease in the M-protein indicating a pathogenetic role of the autoantibody. In three other cases, the IgM was bound to connective tissue structures, two of them also had plasma antibodies against the peri- and endoneurium in the indirect fluorescence test. Finally, two cases showed no reaction of the M-protein against any tissue structures. Since an autoimmune pathogenesis is suspected, the HLA types of seven patients are reported.

A case of malignant lymphoma (plasmacytoid lymphocytic type) with IgM-monoclonal gammopathy is presented. The main site of lesion was in the lung. The sole clinical manifestation was pleuropulmonary involvement with massive pleural effusion. A clue to the diagnosis was given by cytological and immunocytological examination of pleural aspirates. Subsequent immunological survey of serum protein and a bronchial biopsy confirmed the diagnosis.

Immunoblot analysis was performed on the serum from 29 patients with polyneuropathy and monoclonal gammopathy. Nine patients had IgM spikes, and six of the nine had reactivity against myelin-associated glycoprotein (MAG) associated with a slowly progressive, predominantly sensory neuropathy. In contrast, 23 patients who lacked anti-MAG reactivity had more severe sensory motor neuropathy. Thus, IgM monoclonal gammopathy with reactivity against MAG may define a distinct clinical entity.

Abstract 2667 Waldenström Macroglobulinemia (WM) is a B-cell lymphoproliferative disorder characterized by bone marrow infiltration by lymphoplasmacytic lymphoma associated with a monoclonal component of IgM type in the serum. WM is often preceded by an IgM monoclonal gammopathy of undetermined significance (IgM-MGUS). The cumulative probability of progression of IgM-MGUS to WM or to other lymphoproliferative disorders is approximately 1.5% per year. Other mature B-cell neoplasms such as splenic marginal zone lymphoma (SMZL) and B-cell chronic lymphoproliferative disorders (B-CLPD) can carry an IgM monoclonal component and should therefore be considered in differential diagnosis with WM. In a study based on parallel sequencing of the whole genome of lymphoplasmacytic cells and paired normal tissue from WM patients, Treon et al (Blood. 2011;118:Abstract 300) have identified a highly recurrent somatic mutation with oncogenic activity in the myeloid differentiation primary response (MYD88) gene, leading to a change from leucine to proline at position 265 of the aminoacid sequence [MYD88 (L265P)]. Targeted Sanger resequencing showed MYD88 (L265P) in 90% of WM patients, but only in a minority of patients with IgM-MGUS or other mature B-cell neoplasms such as SMZL. We developed an allele-specific PCR for the MYD88 (L265P) mutation, and studied 58 patients with WM, 77 with IgM-MGUS, 84 with splenic marginal zone lymphoma (SMZL) and 52 with B-cell chronic lymphoproliferative disorders (B-CLPD). DNA was obtained from bone marrow cells (n=204) and peripheral blood (n=67). The aims of this study were: i) to assess the prevalence of the mutation in WM, IgM-MGUS, SMZL, and B-CLPD; ii) to analyze the relationship between MYD88 (L265P) mutation and clinical phenotype; iii) to evaluate the impact of the mutation on the risk of progression from IgM-MGUS WM or other lymphoproliferative disorders. The MYD88 (L265P) mutation was detected in 58/58 (100%) patients with WM, either asymptomatic (n=39) or symptomatic (n=18), and in 36/77 (47%) patients with IgM-MGUS. In addition, it was detected in 5/84 (6%) patients with SMZL and in 3/52 (6%) with B-CLPD; of these MYD88 (L265P)-positive subjects, 4 SMZL and 2 B-CLPD patients carried a serum IgM monoclonal component, while the remaining B-CLPD patient carried a double (IgM and IgG) monoclonal component. Compared with IgM-MGUS patients with wild-type MYD88, those carrying MYD88 (L265P) had significantly higher levels of IgM (P In conclusion, the findings of this study indicate that: i) the allele-specific PCR we developed is able to detect the MYD88 (L265P) mutation in all patients with WM and in nearly half the patients with IgM-MGUS, and therefore represents a useful diagnostic tool; ii) MYD88 (L265P) is an uncommon molecular lesion in SMZL and in B-CLPD, but is associated with an IgM monoclonal component in the few positive patients, suggesting that some cases of B-CLPD might be included in the spectrum of WM; iii) in IgM-MGUS, the mutation is associated with greater disease burden and higher risk of disease progression, and therefore represents a useful prognostic marker. Disclosures: No relevant conflicts of interest to declare.

Abstract 4139 Background. The presence of a serum IgM monoclonal component is associated with a spectrum of lymphoid disorders including Waldenström Macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (MGUS) and IgM-related disorders (IgM-RD). Limited information is available on immunoglobulin heavy chain (IGH) gene rearrangement in this setting. Purpose. The aim of this study was to analyze IGHV-D-J rearrangements in a large series of patients (pts) and to compare the gene usage across different monoclonal IgM disorders. Patients and methods. We analyzed 107 pts including 52 WM, 47 IgM MGUS and 8 IgM-RD. Diagnosis was made according to the consensus criteria proposed at the 2nd International Workshop on WM. Mononuclear cells were obtained from bone marrow in all pts. IGHV-D-J rearrangements were amplified and directly sequenced from cDNA using primers specific for each of the leader sequences of HV1-6 subgroups in combination with a joining heavy chain (JH) consensus primer or cμ constant region primer. Sequences were aligned to ImMunoGeneTics sequence directory using the IMGT V-QUEST analysis software. Results. A complete productive monoclonal IGHV-D-J rearrangement was obtained in 84/107 cases (78%). Using a homology cut-off value of 98% to the nearest germline gene, we observed mutated IGHV in 79/84 pts (94%) and unmutated IGHV in 5 (6%). The frequency of IGHV, IGHD and IGHJ gene usage is shown in the table. The most common IGHV subgroup was IGHV3, which was found in 69/84 cases (82%). The individual IGHV genes most frequently used were IGHV3-23 (20/84, 24%) and IGHV3-7 (10/84, 12%). IGHD segments were assignable in 83 out of 84 rearrangements. The most represented IGHD subgroups were IGHD3 (23/83, 28%), IGHD6 (16/83, 19%) and IGHD2 (15/83, 18%). The most common individual IGHD genes were IGHD6-19 (10/83, 12%) and IGHD2-2 (8/83, 10%). The analysis of IGHJ genes showed a preferential usage of IGHJ4 gene (56/84, 67%) and IGHJ4*02 allele (54/84, 64%). The median HCDR3 length was 13 amino acids (range: 5–29). We found an association between IGHV3 and IGHJ4 subgroups (p=0.01), while no association was found between IGHV and IGHD (p=0.8), and between IGHD and IGHJ subgroups (p=0.8). We compared IGH rearrangement features in pts with WM, MGUS and IgM-RD. A complete productive monoclonal IGHV-D-J rearrangement was detected in a higher percentage of WM pts (47/52, 90%) as compared to MGUS (31/47, 66%) and IgM-RD pts (6/8, 75%) (p=0.01). The proportion of mutated IGHV cases was similar in the three groups (p=0.6). Regarding specific gene usage, there was a trend toward a higher usage of IGHV3-23 gene in WM (14/47, 30%) as compared to MGUS (4/31, 13%) (p=0.07). On the contrary, there was no difference in distribution of IGHD subgroups (p=0.13) and IGHJ genes (p=0.5). The median HCDR3 length was similar in WM, MGUS and IgM-RD (p=0.6). We also compared IGHV usage with clinical characteristics of pts. Interestingly, we found that autoimmune manifestations were more frequently observed in pts carrying IGHV4-34 gene (3/4, 75%) as compared to pts using alternative genes (8/80 pts, 10%) (p=0.006). Autoimmune phenomena associated with IGHV4-34 gene were represented by cold agglutinin haemolytic anemia in 2 pts with IgM-RD and 1 with WM. Conclusions: the identification of a monoclonal IGHV-D-J rearrangement seems more feasible in WM as compared to MGUS and IgM-RD. In all three groups, the majority of cases are mutated, confirming the derivation of the clone from a post-germinal center cell. This study shows a preferential usage of VH3 subgroup and in particular of VH3-23 gene, with a trend for a higher usage in WM as compared to other IgM disorders. A higher prevalence of autoimmune manifestations was observed in pts carrying VH4-34 gene. Disclosures: No relevant conflicts of interest to declare.

Background Fibrillary glomerulonephritis (FGN) is a rare primary glomerular disease that seldom coexists with other diseases. Membranoproliferative glomerulonephritis is a pathologic finding of renal lesions associated with IgM-secreting monoclonal proliferations. We present a case study of a patient with unusual simultaneous FGN and IgM-related renal disorder in nonmalignant monoclonal IgM gammopathy. Case presentation A 63-year-old male presented with nephrotic syndrome and elevated serum creatinine levels. Laboratory examination revealed elevated levels of serum IgM and low C3 levels. Serum and urine immunofixation electrophoresis showed a monoclonal IgM with a kappa light chain. A bone marrow biopsy revealed less than 5 % bone marrow infiltration by lymphoplasmacytic lymphoma, and a renal biopsy revealed mesangiocapillary glomerulonephritis on light microscopy. Immunofluorescent and immunohistochemical staining indicated granular deposits of immunoglobulin G in the mesangium and granular deposits of immunoglobulin M and κ light chains along the capillary wall. Electron microscopy revealed randomly arranged nonbranching fibrils of approximately 15 nm in diameter in the glomerular mesangium and subendothelial electron-dense deposits. According to these results, we confirmed FGN and membranoproliferative glomerulonephritis, which were attributed to monoclonal IgM deposits. Conclusion To the best of our knowledge, this is the first report of simultaneous FGN and membranoproliferative glomerulonephritis in nonmalignant IgM monoclonal gammopathy.

We studied the frequency and clinical correlates of different IgM specificities in 75 patients with neuropathy associated with IgM monoclonal gammopathy. Patients were tested for IgM reactivity with the myelin-associated glycoprotein, PO, neurofilaments, and tubulin by immunoblot; with GM1, asialo-GM1, GM2, GD1a, GD1b, sulfatide, and chondroitin sulfate C by enzyme-linked immunosorbent assay; and with brain and nerve glycolipids by overlay highperformance thin-layer chromatography. Forty-two patients (56%) had high titers of IgM antibodies to MAG; 4 (5%), to sulfatide (1 also to myelin-associated glycoprotein); 4 (5%), to the 200-kd neurofilament (2 also to myelin-associated protein); and 1 each, to GD1b and chondroitin sulfate C. No reactivity was found in 26 patients (35%). More patients with anti–myelin-associated glycoprotein IgM (62%) than with unknown IgM reactivity (31%) had a predominantly sensory neuropathy (p < 0.025). Nerve conduction findings were consistent with a demyelinating neuropathy in 77% of patients reactive to myelin-associated glycoprotein and 24% with unknown reactivity (p < 0.0001) and the mean conduction velocity of peroneal nerve was lower in the former group (22.9 m/sec) than in the latter group (39.6 m/sec) (p < 0.000001). Patients with anti–sulfatide IgM had a sensorimotor neuropathy with morphological evidence of demyelination while anti–neurofilament IgM was not associated with homogeneous findings. Patients with anti–GD1b or anti–chondroitin sulfate C IgM had a predominantly motor impairment. The frequent occurrence of anti–neural IgM antibodies in neuropathy associated with IgM gammopathy, and their frequent, though not constant association with similar neuropathy features, support their possible pathogenetic role in the neuropathy.

A highly recurrent somatic L265P mutation in the TIR domain of the signaling adapter MYD88 constitutively activates NF-κB. It occurs in nearly all human patients with Waldenström’s macroglobulinemia (WM), a B cell malignancy caused by IgM-expressing cells. Here, we introduced an inducible leucine to proline point mutation into the mouse Myd88 locus, at the orthologous position L252P. When the mutation was introduced early during B cell development, B cells developed normally. However, IgM-expressing plasma cells accumulated with age in spleen and bone, leading to more than 20-fold elevated serum IgM titers. When introduced into germinal center B cells in the context of an immunization, the Myd88L252P mutation caused prolonged persistence of antigen-specific serum IgM and elevated numbers of antigen-specific IgM plasma cells. Myd88L252P-expressing B cells switched normally, but plasma cells expressing other immunoglobulin isotypes did not increase in numbers, implying that IgM expression may be required for the observed cellular expansion. In order to test whether the Myd88L252P mutation can cause clonal expansions, we introduced it into a small fraction of CD19-positive B cells. In this scenario, five out of five mice developed monoclonal IgM serum paraproteins accompanied by an expansion of clonally related plasma cells that expressed mostly hypermutated VDJ regions. Taken together, our data suggest that the Myd88L252P mutation is sufficient to promote aberrant survival and expansion of IgM-expressing plasma cells which in turn can cause IgM monoclonal gammopathy of undetermined significance (MGUS), the premalignant condition that precedes WM.