Peripheral neuropathies associated with monoclonal proteins

High-affinity heterotetramer formation between the large myelin-associated glycoprotein and the dynein light chain DYNLL1

The close association of myelinated axons and their myelin sheaths involves numerous intercellular molecular interactions. For example, myelin-associated glycoprotein (MAG) mediates myelin-to-axon adhesion and signalling via molecules on the axonal surface. However, knowledge about intracellular binding partners of myelin proteins, including MAG, has remained limited. The two splice isoforms of MAG, S- and L-MAG, display distinct cytoplasmic domains and spatiotemporal expression profiles. We used yeast two-hybrid screening to identify interaction partners of L-MAG and found the dynein light chain DYNLL1 (also termed dynein light chain 8). DYNLL1 homodimers are known to facilitate dimerization of target proteins. L-MAG and DYNLL1 associate with high affinity, as confirmed with recombinant proteins in vitro. Structural analyses of the purified complex indicate that the DYNLL1-binding segment is localized close to the L-MAG C terminus, next to the Fyn kinase Tyr phosphorylation site. The crystal structure of the complex between DYNLL1 and its binding segment on L-MAG shows 2 : 2 binding in a parallel arrangement, indicating a heterotetrameric complex. The homology between L-MAG and previously characterized DYNLL1-ligands is limited, and some details of binding site interactions are unique for L-MAG. The structure of the complex between the entire L-MAG cytoplasmic domain and DYNLL1, as well as that of the extracellular domain of MAG, were modelled based on small-angle X-ray scattering data, allowing structural insights into L-MAG interactions on both membrane surfaces. Our data imply that DYNLL1 dimerizes L-MAG, but not S-MAG, through the formation of a specific 2 : 2 heterotetramer. This arrangement is likely to affect, in an isoform-specific manner, the functions of MAG in adhesion and myelin-to-axon signalling. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Read the Editorial Highlight for this article on page 712.

Plasma-exchange in Chronic Peripheral Neurological Disorders

We investigated 19 patients affected by chronic peripheral neurological disorders treated with therapeutic plasma exchange (TPE) to verify the efficacy of the therapeutic protocol used in these diseases.

Every patient was clinically considered after 5 TPE. Those who showed an improvement started chemotherapy and continued TPE at the rate of 2 procedures/week for 2 weeks, then 1 procedure/week for 1 month and finally 1 procedure every 2 weeks for 2 months. Intravenous immunoglobulins (IVIg) were infused at the end of apheretic treatment in one of the patients affected by neurological disorders due to monoclonal gammopathy undetermined significance. HCV-positive patients with cryoglobulins were treated with α-interferon (α-IFN) for 6 months before TPE. Eleven patients (58%) had a symptomatic improvement, 2 (1.5%) stopped TPE treatment owing to side effects and 6 (31.5%) did not respond to apheretic therapy.

In order to improve the advantages of TPE we suggest using IVIg at the end of apheretic therapy, while in HCV-positive patients, at least one year of α-IFN therapy is required before initiating TPE.

[Clinical characteristics of pain syndrome in patients with multiple myeloma]

AIM

To study pain syndrome characteristics in the trunk and extremities of patients with multiple myeloma (MM).

MATERIAL AND METHODS

The study involved 120 patients with MM, aged from 34 to 83 years. The duration of disease was 2-37 months.

RESULTS AND CONCLUSION

The pain syndrome of trunk and extremity localization was revealed in 94% patients, its intensity according to the VAS was 65.5±25.4 mm. At all stages of disease, moderate to severe pain, predominantly related to polyneuropathy (PNP), radiculopathy and osteodestruction, was more frequent. Radicular pain syndrome was revealed in 46% of all MM patients, and in the majority of cases (92%), there were bone destruction lesions. The character of pain in MM should be specified to optimize further management of the patient.

Cryptogenic sensory polyneuropathy

Chronic sensory or sensorimotor polyneuropathy is a common cause for referral to neurologists. Despite extensive diagnostic testing, up to one-third of these patients remain without a known cause, and are referred to as having cryptogenic sensory peripheral neuropathy. Symptoms progress slowly. On examination, there may be additional mild toe flexion and extension weakness. Electrophysiologic testing and histology reveals axonal neuropathy. Prognosis is usually favorable, as most patients maintain independent ambulation. Besides patient education and reassurance, management is focused on pharmacotherapy for neuropathic pain and physical therapy for balance training, and, occasionally, assistive devices.

Anti-myelin-associated glycoprotein peripheral neuropathy as the only presentation of low grade lymphoma: a case report

Peripheral nervous system involvement has been reported in systemic B or T cell lymphoma and may result from many mechanisms. We present a case of 59-year-old Caucasian man presented with a three years history of progressively worsening peripheral neuropathy with no obvious reason. An extensive workup revealed anti-myelin-associated glycoprotein neuropathy as the only presenting feature of low grade B cell Lymphoma.

POEMS syndrome

POEMS syndrome is a rare paraneoplastic syndrome secondary to a plasma cell dyscrasia. Recognition of the complex of a combination of peripheral neuropathy, organomegaly, endocrinopathy, monoclonal plasmaproliferative disorder, skin changes, papilledema, extravascular volume overload (peripheral edema, pleural effusions, ascites), sclerotic bone lesions, thrombocytosis, Castleman disease is the first step in effectively managing the disease. A rise in the blood levels of vascular endothelial growth factor is usually confirmatory. More than 95% of patients will have monoclonal lambda sclerotic plasmacytoma(s) or bone marrow infiltration. In patients with a dominant sclerotic plasmacytoma, first line therapy should include radiation to the lesion. Retrospective analysis and personal experience would dictate that systemic therapy be considered for patients with diffuse sclerotic lesions or absence of any bone lesion and for those who have not demonstrated stabilization of their disease 3 to 6 months after completing radiation therapy. For those patients with diffuse disease, systemic therapy is indicated. Useful approaches include therapy with corticosteroids, low dose alkylator therapy, and high dose chemotherapy with peripheral blood stem cell transplant. Until the pathogenesis is fully understood, these are the mainstays of treatment for patients with POEMS syndrome. The role of anti-VEGF therapies, immune modulatory drugs, and proteasome inhibitors has not yet been defined, but drugs with known high rates of treatment related neuropathy should not be considered as first line therapy.

Plasma cell dyscrasia with polyneuropathy--POEMS syndrome presenting with vasculitic skin lesions and responding to combination chemotherapy

We report a 61-year-old male patient who presented with severe sensorimotor neuropathy, leg edema and skin lesions with M-paraprotein and 50% plasma cells in the bone marrow. The POEMS (Crow-Fukase) syndrome was diagnosed and the skin lesions were compatible with vasculitis according to the histopathology. The patient was treated with aggressive combined chemotherapy, which induced improvement in both the clinical and laboratory parameters of his disease. To the best of our knowledge this is the first report of a vasculitic process underlying the skin changes in the POEMS syndrome. Our findings may shed light on the unknown pathogenesis of this syndrome and the successful results of treatment support the adoption of an aggressive therapeutic approach in symptomatic patients.

The polyneuropathy associated with Waldenström's macroglobulinaemia can be treated effectively with chemotherapy and the anti-CD20 monoclonal antibody rituximab

A 50-year-old male developed headache, impaired balance, visual defects and severe deafness. Ten months later he presented with markedly reduced power and tremor of his right arm. Waldenström's macroglobulinaemia (WM) with accompanying polyneuropathy was diagnosed. The patient received chemotherapy, which resulted in a partial improvement of the arm tremor. Subsequently, he was treated with rituximab (4 x 375 mg/m2), leading to complete resolution of the tremor and the paresis of his arm. Additionally, his headache and imbalance disappeared. Fifteen months after rituximab therapy he remained free of any neurological symptoms. This is the first report showing that WM-associated polyneuropathy can be treated effectively with a combination of chemotherapy and the anti-CD20 monoclonal antibody rituximab.

Waldenström's macroglobulinemia resulting from localized gastric lymphoplasmacytoid lymphoma

A patient with a high level serum monoclonal IgM lambda paraprotein (3,850 mg/dL) was found to have a mass infiltrating the gastric mucosa. Gastric biopsy with immunohistochemical stains showed a B-cell lymphoplasmacytoid infiltrate expressing IgM lambda, consistent with Waldenström's macroglobulinemia. The patient's response to gastric radiation indicated that the primary source of the macroglobulinemia was the stomach. This is an extremely rare presentation, with only six other reported cases of this entity with gastric involvement.

Rapidly deteriorating polyneuropathy associated with osteosclerotic myeloma responsive to intravenous immunoglobulin and radiotherapy

Osteosclerotic myeloma is a plasma-cell dyscrasia characterized by osteosclerotic bone lesions, which may be associated with progressive demyelinating polyneuropathy. We describe a 49-year-old patient with rapidly deteriorating polyneuropathy associated with osteosclerotic myeloma, who responded favorably to a combination of intravenous immunoglobulin and radiotherapy.

Prognosis of patients with primary systemic amyloidosis who present with dominant neuropathy

BACKGROUND

Primary systemic amyloidosis is an uncommon disorder associated with the desposition of fragments of immunoglobulin light chains in a variety of tissues. Some patients present with peripheral neuropathy. The prognosis of these patients is not clear.

METHODS

We searched the medical records of all patients seen at the Mayo Clinic between January 1, 1978 and December 31, 1994 with the diagnosis of amyloidosis. Twenty-six patients with sural nerve biopsy-proven amyloid neuropathy and a documented monoclonal protein in the serum or urine were studied.

RESULTS

The most common symptoms that led to the diagnosis of primary amyloid neuropathy were paresthesias (81%), muscle weakness (65%), and numbness (58%). The median duration of symptoms before diagnosis was 29 months. Symptoms of autonomic neuropathy were present at diagnosis in 17 patients (65%). Other organs were involved in most patients. The monoclonal light chain protein detected was lambda in 18 patients (69%) and kappa in 8 (31%). The neuropathy was chronic, debilitating, and showed relentless progression. Twenty-two patients (85%) died (median survival 25 months) and 4 patients were alive at a median follow-up of 4.5 years. Progressive amyloidosis was the cause of death in most patients. Survival was significantly better in the patients with a serum albumin level >3 g/dL (median survival 31 months compared with 18 months; P <0.01, log-rank test).

CONCLUSIONS

Patients with primary systemic amyloidosis in whom neuropathy is the dominant clinical manifestation often do not receive a diagnosis until years after the onset of symptoms. The prognosis is worse than previously indicated. Neuropathy does not improve with therapy.

Plasma-Exchange in Chronic Peripheral Neurological Disorders

We investigated 19 patients affected by chronic peripheral neurological disorders treated with therapeutic plasma exchange (TPE) to verify the efficacy of the therapeutic protocol used in these diseases.

Every patient was clinically considered after 5 TPE. Those who showed an improvement started chemotherapy and continued TPE at the rate of 2 procedures/week for 2 weeks, then 1 procedure/week for 1 month and finally 1 procedure every 2 weeks for 2 months. Intravenous immunoglobulins (IVIg) were infused at the end of apheretic treatment in one of the patients affected by neurological disorders due to monoclonal gammopathy undetermined significance. HCV-positive patients with cryoglobulins were treated with α-interferon (α-IFN) for 6 months before TPE.

Eleven patients (58%) had a symptomatic improvement, 2 (1.5%) stopped TPE treatment owing to side effects and 6 (31.5%) did not respond to apheretic therapy.

In order to improve the advantages of TPE we suggest using IVIg at the end of apheretic therapy, while in HCV-positive patients, at least one year of α-IFN therapy is required before initiating TPE.

Antibody panels in idiopathic polyneuropathy and motor neuron disease

We prospectively evaluated patients with idiopathic polyneuropathy (PN) and motor neuron disease (MND) with commercial antibody (Ab) panels. Patients with sensorimotor PN received a "sensorimotor neuropathy profile" [3-sulfated glucuronyl paragloboside (SGPG)/myelin-associated glycoprotein (MAG), GM1, asialo-GM1, GD1b, Hu, sulfatide]. Motor neuropathy or MND patients underwent a "motor neuropathy profile" (SGPG/MAG, GM1, asialo-GM1). Seven of 78 patients (9.0%) with sensorimotor PN and 3 of 44 patients (6.8%) with MND had abnormal panels. None of 60 patients with axonal sensory or sensorimotor PN had antisulfatide Ab. Seven of 13 patients (54%) with multifocal motor neuropathy had abnormal panels, with 6 seropositive to GM1. We found abnormal Ab panels in fewer than 10% of patients with idiopathic sensorimotor PN and MND. Moreover, abnormal Ab tests often did not relate to the clinical context. Our data do not support the use of commercial Ab panels in the evaluation of patients with idiopathic PN or MND.

Marked improvement of severe polyneuropathy associated with multifocal osteosclerotic myeloma following surgery, radiation, and chemotherapy

We describe a patient with a 3 year history of progressive polyneuropathy that rendered him severely quadriparetic and bedridden. Work up revealed an IgG lambda monoclonal spike and multifocal osteosclerotic myeloma. Remarkable improvement followed combined treatment with surgical excision, radiation therapy, and chemotherapy using chlorambucil, danazol, and hydrocortisone. Hence, we believe that aggressive local therapy associated with systemic chemotherapy should be considered in severely affected patients with multifocal osteosclerotic myeloma and peripheral neuropathy.

Peripheral nerve amyloidosis

Peripheral nerve amyloidosis is the cardinal feature of familial amyloid polyneuropathy (FAP) but can also be seen in primary light chain (AL) amyloidosis and dialysis (beta 2-microglobulin) related amyloidosis. The generalized neuropathy seen in all forms of peripheral nerve amyloidosis is similar, characterized by a severe progressive mixed neuropathy with autonomic dysfunction. Pathologically, amyloid is found in the peripheral nervous system as amorphous, eosinophilic, extracellular deposits. FAP is most commonly associated with variant plasma transthyretin (TTR), although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now at least 36 point mutations in the TTR gene associated with FAP and these continue to be described. Recent studies on the possible role individual point mutations in the TTR gene may play in amyloidosis have helped give us an insight into the mechanisms behind peripheral nerve amyloidosis. This article reviews the clinical and pathological features of the peripheral nerve amyloidosis and discusses theories of amyloidogenesis based on studies of FAP.

Neuropathy associated with "benign" anti-myelin-associated glycoprotein IgM gammopathy: clinical, immunological, neurophysiological pathological findings and response to treatment in 33 cases

We studied 33 patients presenting with a peripheral neuropathy associated with non-malignant anti-myelin-associated glycoprotein (MAG) IgM monoclonal gammopathy (MG) in an attempt to delineate their clinical, immunological, electrophysiological and pathological characteristics; we also reviewed our experience concerning long-term follow-up and therapy. Peripheral neuropathy associated with non-malignant anti-MAG IgM MG was observed mostly in males (sex ratio 7.2), and mean age at onset was 67 years (range 46-81). A predominantly sensory pattern was noted in more than 80% of cases, although some patients were affected by a predominantly motor peripheral neuropathy. Although disease progression was slow in most cases, 45% of patients suffered severe disability, and in 2 cases, the patient's death appeared to stem directly from the neuropathy. The electrophysiological findings were indicative of a demyelinating process in 90% of cases, and electron microscopic examination of nerve biopsy specimens demonstrated widening of the myelin lamellae in more than 95% of cases. Most of our patients showed a disappointing response to steroids and chemotherapy or plasma exchanges. Intravenous immune globulin, evaluated in 17 patients, had a transient, mostly subjective effect in 35% and led to a clear-cut improvement in 24% of cases. We did not observe any correlation between the severity of the clinical picture and the anti-sulphoglucuronyl paragloboside antibody titre; in individual cases, clinical improvement occurred without lowering of IgM levels. Although the severity and the rate of progression may greatly vary from patient to patient, the combination of clinical, electrophysiological and pathological features delineates a characteristic pattern in peripheral neuropathy associated with non-malignant anti-MAG IgM MG.

Human immunoglobulin M paraproteins cross-reactive with Neisseria meningitidis group B polysaccharide and fetal brain

Three hundred fifty-nine serum samples from patients with immunoglobulin M (IgM) or IgG monoclonal gammopathies were tested for binding to the capsular polysaccharide (PS) of Neisseria meningitidis group B (MenB PS, poly-alpha[2-->8]-N-acetylneuraminic acid). Of 159 IgM paraproteins, 7 (4.4%) were positive, compared with 0 of 200 IgG paraproteins (P < 0.05). Since MenB PS reactivity was limited to the IgM paraproteins, the 159 IgM paraproteins were tested by enzyme-linked immunosorbent assay (ELISA) for reactivity with seven other bacterial PSs. None reacted with meningococcal A or C, Haemophilus influenzae type b, or Streptococcus pneumoniae type 3, 6, 14, or 23 PS. The specificity of the MenB PS-reactive antibodies was confirmed by demonstration of binding to N. meningitidis group B cells but not to a capsular PS-deficient mutant and by specific inhibition of binding to solid-phase MenB PS by soluble MenB PS in an ELISA. Five of five antibodies tested protected infant rats from bacteremia caused by Escherichia coli K1, an organism with a PS capsule that also is composed of poly-alpha[2-->8]-N-acetylneuraminic acid. Each of the seven MenB PS-reactive paraproteins had autoantibody activity as defined by binding to homogenates of calf brain in a radioimmunoassay. For six of the seven antibodies, binding to calf brain was inhibited by the addition of soluble MenB PS. Thus, approximately 4% of human IgM paraproteins have autoantibody activity to poly-alpha[2-->8]-N-acetylneuraminic acid, an antigen expressed in fetal brain and cross-reactive with the MenB capsular PS. The reason for this skewing of the IgM paraprotein repertoire toward reactivity with poly-alpha[2-->8]-N-acetylneuraminic acid antigenic determinants is unknown.