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Introduction Our aim in this study was to identify the prevalence and clinical characteristics of LRP4/agrin‐antibody–positive double‐seronegative myasthenia gravis (DNMG). Methods DNMG patients at 16 sites in the United States were tested for LRP4 and agrin antibodies, and the clinical data were collected. Results Of 181 DNMG patients, 27 (14.9%) were positive for either low‐density lipoprotein receptor–related protein 4 (LRP4) or agrin antibodies. Twenty‐three DNMG patients (12.7%) were positive for both antibodies. More antibody‐positive patients presented with generalized symptoms (69%) compared with antibody‐negative patients (43%) (P ≤ .02). Antibody‐positive patients’ maximum classification on the Myasthenia Gravis Foundation of America (MGFA) scale was significantly higher than that for antibody‐negative patients (P ≤ .005). Seventy percent of antibody‐positive patients were classified as MGFA class III, IV, or V compared with 39% of antibody‐negative patients. Most LRP4‐ and agrin‐antibody–positive patients (24 of 27, 89%) developed generalized myathenia gravis (MG), but with standard MG treatment 81.5% (22 of 27) improved to MGFA class I or II during a mean follow‐up of 11 years. Discussion Antibody‐positive patients had more severe clinical disease than antibody‐negative patients. Most DNMG patients responded to standard therapy regardless of antibody status.

ObjectiveTo define the clinical phenotype of dermatomyositis (DM) with anti-Mi2 autoantibodies.MethodsIn this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up in patients with anti-Mi2–positive DM were compared to patients with anti-Mi2–negative DM, antisynthetase syndrome (AS), and immune-mediated necrotizing myopathy (IMNM). Longitudinal anti-Mi2 autoantibody titers were assessed.ResultsA total of 58 patients with anti-Mi2–positive DM, 143 patients with anti-Mi2–negative DM, 162 patients with AS, and 170 patients with IMNM were included. Among patients with anti-Mi2–positive DM, muscle weakness was present in 60% at disease onset and occurred in 98% during longitudinal follow-up; fewer patients with anti-Mi2–negative DM developed weakness (85%; p = 0.008). Patients with anti-Mi2–positive DM were weaker and had higher creatine kinase (CK) levels than patients with anti-Mi2–negative DM or patients with AS. Muscle biopsies from patients with anti-Mi2–positive DM had prominent necrosis. Anti-Mi2 autoantibody levels correlated with CK levels and strength (p < 0.001). With treatment, most patients with anti-Mi2–positive DM had improved strength and CK levels; among 10 with multiple serum samples collected over 4 or more years, anti-Mi2 autoantibody titers declined in all and normalized in 3, 2 of whom stopped immunosuppressant treatment and never relapsed. Patients with anti-Mi2–positive DM had less calcinosis (9% vs 28%; p = 0.003), interstitial lung disease (5% vs 16%; p = 0.04), and fever (7% vs 21%; p = 0.02) than did patients with anti-Mi2–negative DM.ConclusionsPatients with anti-Mi2–positive DM have more severe muscle disease than patients with anti-Mi2–negative DM or patients with AS. Anti-Mi2 autoantibody levels correlate with disease severity and may normalize in patients who enter remission.

Rituximab is a chimeric monoclonal antibody that binds CD20 and causes the depletion of B-cell subsets. Although initially designed to treat lymphoma, it has found wide use in the management of various autoimmune conditions, including myasthenia gravis (MG), an autoimmune disorder of the neuromuscular junction. Treated myasthenia patients are often on an oral steroid-sparing agent. To determine the safety of stopping oral steroid-sparing agents at the initiation of rituximab therapy and its effectiveness we reviewed the records of 27 MG patients with rituximab, including 13 with anti-MuSK+ MG, 10 with anti-AChR+ MG, and 4 double seronegative MG patients. All patients that were on an oral steroid-sparing agent (21 of 27) were able to stop it, and they did not require re-introduction of the medication. Also, the daily prednisone dosage was significantly decreased in 20/24 patients across all three serotype groups. MGFA post intervention status analysis also showed 15/27 of all patients achieved minimal manifestation status or remission across all groups. Antibody titers decreased dramatically and promptly in anti-MuSK+ MG patients. Our data suggests that stopping oral steroid-sparing agents at initiation of rituximab therapy is safe. Also, our data indicates that rituximab is highly effective in the management of seropositive MG patients.

Objective Although more than a dozen myositis-specific autoantibodies (MSAs) have been identified, most patients with myositis are positive for a single MSA. The specific overexpression of a given myositis autoantigen in myositis muscle has been proposed as initiating and/or propagating autoimmunity against that particular autoantigen. The present study was undertaken to test this hypothesis. Methods In order to quantify autoantigen RNA expression, RNA sequencing was performed on muscle biopsy samples from control subjects, MSA-positive patients with myositis, regenerating mouse muscles, and cultured human muscle cells. Results Muscle biopsy samples were available from 20 control subjects and 106 patients with autoantibodies recognizing hydroxymethylglutaryl-coenzyme A reductase (n = 40), signal recognition particles (n = 9), Jo-1 (n = 18), nuclear matrix protein 2 (n = 12), Mi-2 (n = 11), transcription intermediary factor 1γ (n = 11), or melanoma differentiation-associated protein 5 (n = 5). The increased expression of a given autoantigen in myositis muscle was not associated with autoantibodies recognizing that autoantigen (all q > 0.05). In biopsy specimens from both myositis muscle and regenerating mouse muscles, autoantigen expression correlated directly with the expression of muscle regeneration markers and correlated inversely with the expression of genes encoding mature muscle proteins. Myositis autoantigens were also expressed at high levels in cultured human muscle cells. Conclusion Most myositis autoantigens are highly expressed during muscle regeneration, which may relate to the propagation of autoimmunity. However, factors other than overexpression of specific autoantigens are likely to govern the development of unique autoantibodies in individual patients with myositis.

Sporadic inclusion body myositis (IBM) is the most common acquired muscle disease in adults over age 50, yet it remains unclear whether the disease is primarily driven by T cell-mediated autoimmunity. IBM muscle biopsies exhibit nuclear clearance and cytoplasmic aggregation of TDP-43 in muscle cells, a pathologic finding observed initially in neurodegenerative disease, and nuclear loss of TDP-43 in neurons causes aberrant RNA splicing. Here, we show that loss of TDP-43 splicing repression, as determined by inclusion of cryptic exons, occurs in skeletal muscle of IBM patients. Out of 119 muscle biopsies tested, RT-PCR-mediated detection of cryptic exon expression is 84% sensitive and 99% specific for diagnosing IBM, indicating utility as a functional and diagnostic biomarker. To determine the role of T cells in pathogenesis, we generated a novel xenograft model by transplanting human IBM muscle into the hindlimb of immunodeficient mice. Xenografts from IBM patients display robust regeneration of human myofibers and recapitulate both inflammatory and degenerative features of the disease. Myofibers in IBM xenografts are invaded by human, oligoclonal CD8+ T cells and exhibit MHC-I upregulation, rimmed vacuoles, mitochondrial pathology, p62-positive inclusions, and nuclear clearance and cytoplasmic aggregation of TDP-43, resulting in expression of cryptic exons. Depletion of human T cells within IBM xenografts by treating mice intraperitoneally with anti-CD3 (OKT3) suppresses MHC-I upregulation, but rimmed vacuoles and loss of TDP-43 function persist. These data suggest that myofiber degeneration occurs independent of T cells, and muscle cell-intrinsic mechanisms, such as loss of TDP-43 splicing repression, drive IBM pathogenesis.One Sentence SummaryDepletion of T cells in a xenograft model of sporadic inclusion body myositis suppresses inflammation but not TDP-43 pathology or muscle degeneration.

Objective Mitochondrial DNA mutations are associated with an increased risk of heart disease. Whether an increased prevalence of cardiovascular disease is present in patients presenting with mitochondrial abnormalities on skeletal muscle biopsy remains unknown. This study was designed to determine the prevalence of cardiac conduction disease and structural heart disease in patients presenting with mitochondrial abnormalities on skeletal muscle biopsy. Methods This is a retrospective cohort study of 103 patients with mitochondrial abnormalities on skeletal muscle biopsy who were referred for evaluation of muscle weakness at a single tertiary care referral center from 2012 to 2018. Of these patients, 59 (57.3%) had an electrocardiogram available and were evaluated for the presence of conduction disease. An echocardiogram was available in 43 patients (42%) who were evaluated for the presence of structural heart disease. The prevalence of cardiac disease was compared to control cohort populations (Framingham and the Atherosclerosis Risk in Communities, ARIC cohorts). Results Mitochondrial abnormalities associated with cardiac conduction disease (defined as QRS duration ≥ 120 msec) were present in 8.9%, versus 2.0% (p

ObjectivesTo approximate the rate of familial myasthenia gravis and the coexistence of other autoimmune disorders in the patients and their families.DesignRetrospective cohort study.SettingClinics across North America.ParticipantsThe study included 1032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis.MethodsPhenotype information of 1032 patients diagnosed with AChR-positive myasthenia gravis was obtained from clinics at 14 centres across North America between January 2010 and January 2011. A critical review of the epidemiological literature on the familial rate of myasthenia gravis was also performed.ResultsAmong 1032 patients, 58 (5.6%) reported a family history of myasthenia gravis. A history of autoimmune diseases was present in 26.6% of patients and in 28.4% of their family members.DiscussionThe familial rate of myasthenia gravis was higher than would be expected for a sporadic disease. Furthermore, a high proportion of patients had a personal or family history of autoimmune disease. Taken together, these findings suggest a genetic contribution to the pathogenesis of myasthenia gravis.

Background Complement is likely to have a role in refractory generalised myasthenia gravis, but no approved therapies specifically target this system. Results from a phase 2 study suggested that eculizumab, a terminal complement inhibitor, produced clinically meaningful improvements in patients with anti-acetylcholine receptor antibody-positive refractory generalised myasthenia gravis. We further assessed the efficacy and safety of eculizumab in this patient population in a phase 3 trial. Methods We did a phase 3, randomised, double-blind, placebo-controlled, multicentre study (REGAIN) in 76 hospitals and specialised clinics in 17 countries across North America, Latin America, Europe, and Asia. Eligible patients were aged at least 18 years, with a Myasthenia Gravis-Activities of Daily Living (MG-ADL) score of 6 or more, Myasthenia Gravis Foundation of America (MGFA) class II-IV disease, vaccination against Neisseria meningitides, and previous treatment with at least two immunosuppressive therapies or one immunosuppressive therapy and chronic intravenous immunoglobulin or plasma exchange for 12 months without symptom control. Patients with a history of thymoma or thymic neoplasms, thymectomy within 12 months before screening, or use of intravenous immunoglobulin or plasma exchange within 4 weeks before randomisation, or rituximab within 6 months before screening, were excluded. We randomly assigned participants (1:1) to either intravenous eculizumab or intravenous matched placebo for 26 weeks. Dosing for eculizumab was 900 mg on day 1 and at weeks 1, 2, and 3; 1200 mg at week 4; and 1200 mg given every second week thereafter as maintenance dosing. Randomisation was done centrally with an interactive voice or web-response system with patients stratified to one of four groups based on MGFA disease classification. Where possible, patients were maintained on existing myasthenia gravis therapies and rescue medication was allowed at the study physician's discretion. Patients, investigators, staff, and outcome assessors were masked to treatment assignment. The primary efficacy endpoint was the change from baseline to week 26 in MG-ADL total score measured by worst-rank ANCOVA. The efficacy population set was defined as all patients randomly assigned to treatment groups who received at least one dose of study drug, had a valid baseline MG-ADL assessment, and at least one post-baseline MG-ADL assessment. The safety analyses included all randomly assigned patients who received eculizumab or placebo. This trial is registered with ClinicalTrials.gov, number NCT01997229. Findings Between April 30, 2014, and Feb 19, 2016, we randomly assigned and treated 125 patients, 62 with eculizumab and 63 with placebo. The primary analysis showed no significant difference between eculizumab and placebo (least-squares mean rank 56·6 [SEM 4·5] vs 68·3 [4·5]; rank-based treatment difference -11·7, 95% CI -24·3 to 0·96; p=0·0698). No deaths or cases of meningococcal infection occurred during the study. The most common adverse events in both groups were headache and upper respiratory tract infection (ten [16%] for both events in the eculizumab group and 12 [19%] for both in the placebo group). Myasthenia gravis exacerbations were reported by six (10%) patients in the eculizumab group and 15 (24%) in the placebo group. Six (10%) patients in the eculizumab group and 12 (19%) in the placebo group required rescue therapy. Interpretation The change in the MG-ADL score was not statistically significant between eculizumab and placebo, as measured by the worst-rank analysis. Eculizumab was well tolerated. The use of a worst-rank analytical approach proved to be an important limitation of this study since the secondary and sensitivity analyses results were inconsistent with the primary endpoint result; further research into the role of complement is needed. Funding Alexion Pharmaceuticals.

ObjectivesMyositis is a heterogeneous family of diseases that includes dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotising myopathy (IMNM), inclusion body myositis (IBM), polymyositis and overlap myositis. Additional subtypes of myositis can be defined by the presence of myositis-specific autoantibodies (MSAs). The purpose of this study was to define unique gene expression profiles in muscle biopsies from patients with MSA-positive DM, AS and IMNM as well as IBM.MethodsRNA-seq was performed on muscle biopsies from 119 myositis patients with IBM or defined MSAs and 20 controls. Machine learning algorithms were trained on transcriptomic data and recursive feature elimination was used to determine which genes were most useful for classifying muscle biopsies into each type and MSA-defined subtype of myositis.ResultsThe support vector machine learning algorithm classified the muscle biopsies with >90% accuracy. Recursive feature elimination identified genes that are most useful to the machine learning algorithm and that are only overexpressed in one type of myositis. For example, CAMK1G (calcium/calmodulin-dependent protein kinase IG), EGR4 (early growth response protein 4) and CXCL8 (interleukin 8) are highly expressed in AS but not in DM or other types of myositis. Using the same computational approach, we also identified genes that are uniquely overexpressed in different MSA-defined subtypes. These included apolipoprotein A4 (APOA4), which is only expressed in anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) myopathy, and MADCAM1 (mucosal vascular addressin cell adhesion molecule 1), which is only expressed in anti-Mi2-positive DM.ConclusionsUnique gene expression profiles in muscle biopsies from patients with MSA-defined subtypes of myositis and IBM suggest that different pathological mechanisms underly muscle damage in each of these diseases.

ObjectiveActivation of the type 1 interferon (IFN1) pathway is a prominent feature of dermatomyositis (DM) muscle and may play a role in the pathogenesis of this disease. However, the relevance of the IFN1 pathway in patients with other types of myositis such as the antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) is largely unknown. Moreover, the activation of the type 2 interferon (IFN2) pathway has not been comprehensively explored in myositis. In this cross-sectional study, our objective was to determine whether IFN1 and IFN2 pathways are differentially activated in different types of myositis by performing RNA sequencing on muscle biopsy samples from 119 patients with DM, IMNM, AS, or IBM and on 20 normal muscle biopsies.MethodsThe expression of IFN1- and IFN2-inducible genes was compared between the different groups.ResultsThe expression of IFN1-inducible genes was high in DM, moderate in AS, and low in IMNM and IBM. In contrast, the expression of IFN2-inducible genes was high in DM, IBM, and AS but low in IMNM. The expression of IFN-inducible genes correlated with the expression of genes associated with inflammation and muscle regeneration. Of note, ISG15 expression levels alone performed as well as composite scores relying on multiple genes to monitor activation of the IFN1 pathway in myositis muscle biopsies.ConclusionsIFN1 and IFN2 pathways are differentially activated in different forms of myositis. This observation may have therapeutic implications because immunosuppressive medications may preferentially target each of these pathways.

ObjectiveTo define the clinical phenotype of patients with myositis with anti-U1-ribonucleoprotein (RNP) autoantibodies.MethodsIn this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up in patients with anti-U1-RNP–positive myositis were compared to those with dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), and the antisynthetase syndrome (AS).ResultsTwenty anti-U1-RNP–positive patients, 178 patients with DM, 135 patients with IMNM, and 132 patients with AS were included. Anti-U1-RNP–positive patients were younger (∼37 years) and more likely to be black (60%) than patients with AS, DM, or IMNM. Muscle weakness was a presenting feature in 15% of anti-U1-RNP–positive patients; 80% eventually developed weakness. Four of 7 anti-U1-RNP–positive patients had necrotizing muscle biopsies. Arthritis occurred in 60% of anti-U1-RNP–positive patients; this was increased compared to DM (18%) or IMNM (6%) (all p < 0.01). DM-specific skin features developed in 60% of anti-U1-RNP–positive patients. Interstitial lung disease (ILD) occurred in 45% of anti-U1-RNP–positive patients; fewer patients with DM (13%) and IMNM (6%) and more patients with AS (80%) developed ILD (all p < 0.01). Glomerulonephritis and pericarditis occurred in 25% and 40% of anti-U1-RNP–positive patients, respectively, but rarely in the other groups; these features occurred only in those with coexisting anti-Ro52 autoantibodies. No anti-U1-RNP patient had cancer-associated myositis or died during the study period.ConclusionsPatients with anti-U1-RNP myositis typically present with proximal weakness and necrotizing muscle biopsies. Arthritis, dermatitis, and ILD are the most common extramuscular clinical features. Pericarditis and glomerulonephritis are uniquely found in patients with anti-U1-RNP–positive myositis.

Objective To characterize cellular infiltrates in muscle biopsies from patients with anti-3-hydroxy-3-methyl-gulatryl-CoA reductase (HMGCR)-associated myopathy.

Objective Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disorder due to deficient activity of arylsulfatase A (ASA) that causes accumulation of sulfatide and lysosulfatide. The disorder is associated with demyelination and axonal loss in the central and peripheral nervous systems. The late infantile form has an early-onset, rapidly progressive course with severe sensorimotor dysfunction. The relationship between the degree of nerve damage and (lyso)sulfatide accumulation is, however, not established. Methods In 13 children aged 2–5 years with severe motor impairment, markedly elevated cerebrospinal fluid (CSF) and sural nerve sulfatide and lysosulfatide levels, genotype, ASA mRNA levels, residual ASA, and protein cross-reactive immunological material (CRIM) confirmed the diagnosis. We studied the relationship between (lyso)sulfatide levels and (1) the clinical deficit in gross motor function (GMFM-88), (2) median and peroneal nerve motor and median and sural nerve sensory conduction studies (NCS), (3) median and tibial nerve somatosensory evoked potentials (SSEPs), (4) sural nerve histopathology, and (5) brain MR spectroscopy. Results Eleven patients had a sensory-motor demyelinating neuropathy on electrophysiological testing, whereas two patients had normal studies. Sural nerve and CSF (lyso)sulfatide levels strongly correlated with abnormalities in electrophysiological parameters and large myelinated fiber loss in the sural nerve, but there were no associations between (lyso)sulfatide levels and measures of central nervous system (CNS) involvement (GMFM-88 score, SSEP, and MR spectroscopy). Interpretation Nerve and CSF sulfatide and lysosulfatide accumulation provides a marker of disease severity in the PNS only; it does not reflect the extent of CNS involvement by the disease process. The magnitude of the biochemical disturbance produces a continuously graded spectrum of impairments in neurophysiological function and sural nerve histopathology.

Objective In the context of clinical evaluations performed on our prospective myositis cohort, we noted a striking association of severe cardiac disease in myositis patients with anti-mitochondrial antibodies. We sought to review all cases of anti-mitochondrial antibody (AMA) associated myositis in our cohort to describe the clinical features of this disease subset. Methods We identified 7 patients with confirmed anti-mitochondrial antibodies who presented as an inflammatory myopathy. A retrospective chart review was completed to assess their clinical presentation, laboratory, imaging, electrophysiologic, and histopathologic features. Results One patient presented with dermatomyositis and 6 were classified as polymyositis using Bohan and Peter criteria. In all but one patient, a chronic course of muscle involvement was appreciated with an average of 6.5 years of weakness prior to presentation. Muscle atrophy was often noted, as well as atypical findings of scapular winging in 2 of the patients. Muscle biopsies were consistent with immune-mediated necrotizing myopathy in 4 patients, dermatomyositis in 1, polymyositis in 1 and nonspecific or granulomatous myositis in 1 patient. Changes pointing to mitochondrial alterations were seen in 2 of the 7 patients. Cardiac involvement (including myocarditis, atrial and ventricular arrhythmias, and cardiomyopathy), was seen in 5 out of 7 (71%) of the patients, and usually preceded the muscle involvement. Coexisting autoimmune conditions were seen in 3/7of the patients and included primary biliary cirrhosis, autoimmune hepatitis, psoriasis, and Hashimoto’s thyroiditis. Conclusions Anti-mitochondrial antibodies identify a distinct inflammatory myopathy phenotype that is frequently associated with chronic skeletal muscle disease and severe cardiac involvement. Early recognition of this rare entity as an immune-mediated process is important due to implications for treatment. We propose that anti-mitochondrial antibody status should be determined in patients with a compatible clinical picture.

Mutations in MYH7 cause autosomal dominant Laing distal myopathy. We present a family with a previously reported deletion (c.5186_5188delAGA, p.K1729del). Muscle pathology in one family member was characterized by an inflammatory myopathy with rimmed vacuoles, increased MHC Class I expression, and perivascular and endomysial muscle inflammation comprising CD3(+), CD4(+), CD8(+), and CD68(+) inflammatory cells. Interestingly, this biopsy specimen contained TDP-43, p62, and SMI-31-positive protein aggregates typical of inclusion body myositis. These findings should alert physicians to the possibility that patients with MYH7 mutations may have muscle biopsies showing pathologic findings similar to inclusion body myositis.

A slowly progressive hemiparesis beginning in a single limb with evolution to the ipsilateral limb was originally described in 8 patients in 1906 by Mills. We present 5 cases of progressive hemiparetic corticospinal tract degeneration, identified by the clinical presentation and the exclusion of other etiologies using serological, imaging, and electrodiagnostic studies.

Objective To determine if a unique subtype of scleroderma muscle disease exists by comparing the clinical features of systemic sclerosis (SSc; scleroderma) patients with predominant fibrosis on muscle biopsy to those with inflammatory muscle histopathology. Methods This retrospective, cross-sectional study included SSc patients with muscle weakness and an available muscle biopsy. Biopsies with fibrosis but without inflammation/necrosis were designated as “fibrosing myopathy,” and those with inflammation and/or necrosis were assigned a category of “inflammatory myopathy.” Clinical data, including features of SSc, serum creatine kinase (CK) levels, electromyography, autoantibody profile, and survival, were compared between the 2 groups. Results The study population consisted of 37 weak SSc patients, 8 with fibrosing myopathy and 29 with inflammatory myopathy. Compared to those with inflammatory myopathy, patients with fibrosing myopathy were more likely to have diffuse SSc skin subtype (87% versus 62%; P = 0.18), African American race (62.5% versus 37.9%; P = 0.20), and a lower mean ± SD forced vital capacity (55.5 ± 31.9 versus 66.4 ± 17.6; P = 0.23). They also had lower mean ± SD CK values (516 ± 391 versus 2,477 ± 3,511 IU/liter; P = 0.007) and lower aldolase values (13.8 ± 4.7 versus 27.3 ± 4.7; P = 0.01). Patients with fibrosing myopathy had a significantly higher mortality (5 of 8 [62.5%] versus 4 of 29 [14.3%]; P = 0.005). Conclusion Fibrosing myopathy is a unique histologic subtype of muscle disease among weak patients with SSc and is associated with significantly worse mortality compared to those with inflammation and/or necrosis on muscle biopsy.

The classic phenotype of amyloid myopathy consists of mild proximal weakness, macroglossia, a hoarse voice, and muscle pseudohypertrophy or palpable muscle masses.1–3 A less common presentation has been described with more severe progressive weakness without macroglossia or pseudohypertrophy.1,2 Congophilic amyloid deposition can be seen in intramuscular blood vessel walls (i.e., amyloid angiopathy) and also encircling individual myofibers. As both of these findings represent amyloid within muscle, they are both considered amyloid myopathy. In other organs, a distinction is made between parenchymal pericellular amyloid deposition and amyloid angiopathy. A related disorder with interstitial pericellular deposition of noncongophilic light chains has been described in many other organs, often accompanied by amyloid deposition in blood vessels. Unlike intraparenchymal amyloid deposits which are more frequently lambda, light chain deposition disease (LCDD) is characterized most commonly by kappa deposition.4,5 The diagnosis of amyloid myopathy is often delayed, because monoclonal gammopathies are not detected on initial testing and muscle biopsies are frequently nondiagnostic. Additionally, the EMG findings, symptoms, and course can mimic an inflammatory myopathy.6,7 Although there is limited data on magnetic resonance imaging (MRI) in amyloid myopathy, published literature has stated that amyloidosis should not be included in the differential diagnosis of patients whose MRI scans show significant signal intensity changes within muscles.3 Here we present a patient with progressive proximal lower extremity muscle weakness who was finally diagnosed based on MRI findings atypical for amyloid myopathy, an MRI-directed muscle biopsy revealing unique pathology, and a serum free light chain (FLC) assay confirming a kappa monoclonal gammopathy despite multiple negative serum and urine immunofixations. We review similar published cases and suggest that the spectrum of immunoglobulin deposition in muscle may be similar to other organs, comprising a continuum of parenchymal amyloid deposition, amyloid angiopathy, and noncongophilic light chain deposition. This case also highlights the value of MRI-guided muscle biopsy and the evolving role for serum FLC assays in identifying monoclonal gammopathies.

Detection of autoantibodies associated with neurological disease typically involves immunoprecipitation of radioactively labeled native proteins. We explored whether single receptor subunits, fused to Renilla luciferase (Ruc), could detect patient autoantibodies in Luciferase Immunoprecipitation Systems. Myasthenia Gravis patient sera were tested for conformational autoantibodies to only the α1-subunit of the nicotinic acetylcholine receptor (AChR). Using a panel of 10 AChR-α1 fragments, AChR-α1-Δ5-Ruc demonstrated the highest immunoreactivity with a conformational-specific antibody and the highest sensitivity in a pilot cohort. Testing a larger cohort with AChR-α1-Δ5-Ruc demonstrated 21% sensitivity and 97% specificity. A point mutation within Ruc increased the diagnostic performance of AChR-α1-Δ5 (32% sensitivity, 97% specificity). The (125)I-α-bungarotoxin multi-subunit AChR assay demonstrated 63% sensitivity and 97% specificity. These findings highlight the difficulty in detecting Myasthenia Gravis conformational epitopes across assay formats and lay the foundation for detecting autoantibodies to defined recombinant chains of the AChR and potentially other neurotransmitter receptors.

Objective Autoantibodies against the chromatin remodeler Mi-2 are found in a distinct subset of patients with dermatomyositis (DM). Previous quantitative immunoblotting experiments demonstrated that Mi-2 protein levels are up-regulated in DM muscle. This study was undertaken to define the population of cells expressing high levels of Mi-2 in DM muscle and to explore the regulation and functional role of Mi-2 during muscle regeneration. Methods The expression of Mi-2 was analyzed by immunofluorescence microscopy in human muscle biopsy specimens. In an experimental mouse model, cardiotoxin was used to induce muscle injury and repair, and expression of Mi-2 during muscle regeneration was studied in this model by immunofluorescence and immunoblotting analyses. In addition, a cell culture system of muscle differentiation was utilized to artificially modulate Mi-2 levels during proliferation and differentiation of myoblasts. Results In human DM muscle tissue, increased Mi-2 expression was found preferentially in the myofibers within fascicles affected by perifascicular atrophy, particularly in the centralized nuclei of small perifascicular muscle fibers expressing markers of regeneration. In injured mouse muscle tissue, Mi-2 levels were dramatically and persistently up-regulated during muscle regeneration in vivo. Premature silencing of Mi-2 with RNA interference in vitro resulted in accelerated myoblast differentiation. Conclusion Expression of Mi-2 is markedly up-regulated during muscle regeneration in a mouse model of muscle injury and repair. It is also up-regulated in human DM myofibers expressing markers of regeneration. Results of the in vitro studies indicate that this protein may play a role in modulating the kinetics of myoblast differentiation. Our findings thus suggest that high levels of Mi-2 expression in muscle biopsy tissue from patients with DM reflect the presence of incompletely differentiated muscle cells.

Background: The purpose of the study was to investigate the diagnostic yield and clinical utility of open muscle biopsy and to identify pre-biopsy factors that might predict useful clinical results for suspected myopathy. Methods: Two-hundred fifty-eight muscle biopsies, performed for investigation of suspected myopathy, were evaluated. Results: A specific clinical diagnosis following muscle biopsy was made in 43% of cases. As a result of the biopsy, clinical diagnosis was changed in 47% and treatment was changed in 33% of cases. Results either led to a specific clinical diagnosis or changed the diagnosis/treatment in 74% of patients. Positive family history of myopathy and findings of myopathic irritability on electromyography had a negative predictive value for diagnosis change. Conclusions: Open muscle biopsy is useful in myopathy evaluation in the modern genetic era.

Chronic glutamate toxicity is implicated in the pathogenesis of ALS. The neuropeptide N-acetyl-aspartyl glutamate (NAAG) appears to function both as a storage form for glutamate and as a neuromodulator at glutamatergic synapses. Catabolism of NAAG by N-acetylated-α-linked acidic dipeptidase (NAALADase; also termed glutamate carboxypeptidase II), yields N-acetyl aspartate (NAA) and glutamate. Since prior studies demonstrate an up-regulation of NAALADase in motor cortex and increased levels of NAA and glutamate in the CSF of ALS patients, we hypothesized that inhibition of NAALADase could protect against neuronal degeneration in ALS. Neuroprotective effects of two NAALADase inhibitors were assessed. 2-(Phosphonomethyl)pentanedioic acid (2-PMPA) decreased motor neuron loss and prevented loss of choline acetyltransferase (ChAT) activity in an in vitro model of ALS wherein chronic glutamate toxicity was induced by blocking glutamate transport. Gross morphology was preserved in 2-PMPA-treated cultures. In a SOD-1 transgenic mouse model of ALS, oral administration of a structurally different NAALADase inhibitor (GPI 5693) increased survival by 29 days and delayed onset of clinical symptoms by 17 days. Preliminary analysis of spinal cord pathology revealed severe neuronal depletion and astrocytosis with white matter changes in control mice. In mice treated with GPI 5693, normal neuronal populations with modest vacuolar changes were observed. These data suggest that NAALADase inhibition may provide an exciting therapeutic approach to the devastating disease, ALS.

Background: TCH346 exerts antiapoptotic effects by binding to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and blocking the apoptotic pathway in which GAPDH is involved. Apoptosis is considered to be a key pathogenic mechanism in neurodegenerative diseases including ALS. Methods: Patients were randomly assigned in a double-blind fashion to receive either placebo or one of four doses of TCH346 (1.0, 2.5, 7.5, or 15 mg/day) administered orally once daily for at least 24 weeks. The primary outcome measure was the rate of change in the revised ALS functional rating scale (ALSFRS-R). The trial design included a 16-week lead-in phase to determine each patient9s rate of disease progression. The between treatment comparison was adjusted for the individual pretreatment rates of progression. The study was powered to detect a 25% reduction in the rate of decline of the ALSFRS-R as compared with placebo. Secondary outcome measures included survival, pulmonary function, and manual muscle testing (MMT). Results: Five hundred ninety-one patients were enrolled at 42 sites in Europe and North America. There were no differences in baseline variables. There were no significant differences between placebo and active treatment groups in the mean rate of decline of the ALSFRS-R or in the secondary outcome measures (survival, pulmonary function, and MMT). Conclusion: The trial revealed no evidence of a beneficial effect of TCH346 on disease progression in patients with ALS.

To identify proteins expressed abnormally in facioscapulohumeral muscular dystrophy (FSHD), we extracted soluble proteins from deltoid muscle biopsies from unaffected control and FSHD patients and analyzed them using two-dimensional electrophoresis, mass spectrometry and immunoblotting. Muscles from patients with FSHD showed large increases over controls in a single soluble, 34 kDa protein (pI=5.08) identified by mass spectrometry and immunoblotting as mu-crystallin (CRYM). Soluble fractions of biopsies of several other myopathies and muscular dystrophies showed no appreciable increases in mu-crystallin. Mu-crystallin has thyroid hormone and NADPH binding activity and so may influence differentiation and oxidative stress responses, reported to be altered in FSHD. It is also linked to retinal and inner ear defects, common in FSHD, suggesting that its up-regulation may play a specific and important role in pathogenesis of FSHD.

Importance Myasthenia gravis is a chronic, autoimmune, neuromuscular disease characterized by fluctuating weakness of voluntary muscle groups. Although genetic factors are known to play a role in this neuroimmunological condition, the genetic etiology underlying myasthenia gravis is not well understood. Objective To identify genetic variants that alter susceptibility to myasthenia gravis, we performed a genome-wide association study. Design, Setting, and Participants DNA was obtained from 1032 white individuals from North America diagnosed as having acetylcholine receptor antibody–positive myasthenia gravis and 1998 race/ethnicity-matched control individuals from January 2010 to January 2011. These samples were genotyped on Illumina OmniExpress single-nucleotide polymorphism arrays. An independent cohort of 423 Italian cases and 467 Italian control individuals were used for replication. Main Outcomes and Measures We calculated P values for association between 8 114 394 genotyped and imputed variants across the genome and risk for developing myasthenia gravis using logistic regression modeling. A threshold P value of 5.0 × 10 −8 was set for genome-wide significance after Bonferroni correction for multiple testing. Results In the overall case-control cohort, we identified association signals at CTLA4 (rs231770; P = 3.98 × 10 −8 ; odds ratio, 1.37; 95% CI, 1.25-1.49), HLA-DQA1 (rs9271871; P = 1.08 × 10 −8 ; odds ratio, 2.31; 95% CI, 2.02 - 2.60), and TNFRSF11A (rs4263037; P = 1.60 × 10 −9 ; odds ratio, 1.41; 95% CI, 1.29-1.53). These findings replicated for CTLA4 and HLA-DQA1 in an independent cohort of Italian cases and control individuals. Further analysis revealed distinct, but overlapping, disease-associated loci for early- and late-onset forms of myasthenia gravis. In the late-onset cases, we identified 2 association peaks: one was located in TNFRSF11A (rs4263037; P = 1.32 × 10 −12 ; odds ratio, 1.56; 95% CI, 1.44-1.68) and the other was detected in the major histocompatibility complex on chromosome 6p21 ( HLA-DQA1 ; rs9271871; P = 7.02 × 10 −18 ; odds ratio, 4.27; 95% CI, 3.92-4.62). Association within the major histocompatibility complex region was also observed in early-onset cases ( HLA-DQA1 ; rs601006; P = 2.52 × 10 −11 ; odds ratio, 4.0; 95% CI, 3.57-4.43), although the set of single-nucleotide polymorphisms was different from that implicated among late-onset cases. Conclusions and Relevance Our genetic data provide insights into aberrant cellular mechanisms responsible for this prototypical autoimmune disorder. They also suggest that clinical trials of immunomodulatory drugs related to CTLA4 and that are already Food and Drug Administration approved as therapies for other autoimmune diseases could be considered for patients with refractory disease.

Objective: We examined the sarcolemma of skeletal muscle from patients with facioscapulohumeral muscular dystrophy (FSHD1A) to learn if, as in other murine and human muscular dystrophies, its organization and relationship to nearby contractile structures are altered. Methods: Unfixed biopsies of control and FSHD deltoid and biceps muscles, snapfrozen at resting length, were cryosectioned, indirectly immunolabeled with fluorescent antibodies to sarcolemmal and myofibrillar markers, and examined with confocal microscopy to localize the immunolabeled proteins. Glutaraldehydefixed samples were stained with heavy metals, embedded, thin-sectioned, and examined with electron microscopy to determine the relationship between the sarcolemma and the underlying myofibrils. Results: Confocal microscopy showed that some of the structures at the sarcolemma in FSHD samples were misaligned with respect to the underlying contractile apparatus. Electron microscopy showed a significant increase in the distance between the sarcolemma and the nearest myofibrils, from less than 100nm in controls to values as high as 550nm in FSHD. Interpretation: Our results show that the pathophysiology of FSHD includes novel changes in the organization of the sarcolemma and its association with nearby contractile structures and suggest that, as in other muscular dystrophies, the integrity of the sarcolemma may be compromised in FSHD. Ann Neurol 2006;59:289 –297 Facioscapulohumeral muscular dystrophy (FSHD) causes progressive weakness of skeletal muscle, preferentially affecting muscles of the face, shoulder, and upper arms. 1 It is also associated with high-frequency hearing loss and retinal vascular abnormalities. 2– 6 The relatively high incidence of 1 in 20,000, 7 which makes FSHD the third most common form of muscular dystrophy, can be attributed to its autosomal dominant mode of inheritance and the high frequency of new mutations, which account for approximately 10% of all new FSHD cases. 8 The FSHD mutation is linked to

A 51-year-old man developed progressive debilitating limb and respiratory muscle weakness while undergoing treatment for chronic graft-versus-host disease secondary to allogeneic bone marrow transplant for mantle cell lymphoma. He had a normal serum creatine kinase level and acetylcholine receptor antibodies were negative. Electromyography showed a severe, nonirritable myopathy and a sensory motor axonal polyneuropathy. A muscle biopsy showed a necrotizing, vacuolar myopathy with many fibers containing autophagic and red-rimmed vacuoles, suggestive of an amphiphilic drug myopathy. The patient's strength and function improved significantly after discontinuation of hydroxychloroquine.

Multifocal motor neuropathy (MMN) is a progressive disorder producing asymmetrical weakness and muscle wasting. Case reports suggest that patients with MMN improve after cyclophosphamide therapy, but not after prednisone or plasmapheresis. Because MMN is likely to be immune mediated, we investigated the therapeutic response to human immune globulin (HIG) in an open, uncontrolled trial. Nine patients, ages 28 to 58 years, had chronic, progressive, asymmetrical, predominantly distal, limb weakness for 5 to 18 years. Sensation was normal, and reflexes were reduced asymmetrically. All had physiological evidence of multifocal motor demyelination with partial motor conduction block, and 7 had elevated serum titers of anti-GM1 IgM antibody. All patients were treated with HIG, 1.6 to 2.4 gm/kg, given intravenously over 3 to 5 days. Strength improved in all patients 3 to 10 days after treatment, with improvement peaking at 2 weeks and lasting for an average of 2 months. The range of functional improvement varied from dramatic to mild. The degree of partial motor conduction block was reduced, at least partially, in 7 of 8 patients. The serum anti-GM1 antibody titers did not change. Repeated courses of HIG resulted in similar improvements. We conclude that HIG may be an effective therapy for patients with MMN.

UNLABELLED\ud \ud The neurite outgrowth inhibitor, Nogo-A, has been shown to be overexpressed in skeletal muscle in amyotrophic lateral sclerosis (ALS); it is both a potential biomarker and therapeutic target. We performed a double-blind, two-part, dose-escalation study, in subjects with ALS, assessing safety, pharmacokinetics (PK) and functional effects of ozanezumab, a humanized monoclonal antibody against Nogo-A. In Part 1, 40 subjects were randomized (3∶1) to receive single dose intravenous ozanezumab (0.01, 0.1, 1, 5, or 15 mg/kg) or placebo. In Part 2, 36 subjects were randomized (3∶1) to receive two repeat doses of intravenous ozanezumab (0.5, 2.5, or 15 mg/kg) or placebo, approximately 4 weeks apart. The primary endpoints were safety and tolerability (adverse events [AEs], vital signs, electrocardiogram (ECG), and clinical laboratory tests). Secondary endpoints included PK, immunogenicity, functional endpoints (clinical and electrophysiological), and biomarker parameters. Overall, ozanezumab treatment (0.01-15 mg/kg) was well tolerated. The overall incidence of AEs in the repeat dose 2.5 mg/kg and 15 mg/kg ozanezumab groups was higher than in the repeat dose placebo group and repeat dose 0.5 mg/kg ozanezumab group. The majority were considered not related to study drug by the investigators. Six serious AEs were reported in three subjects receiving ozanezumab; none were considered related to study drug. No study drug-related patterns were identified for ECG, laboratory, or vital signs parameters. One subject (repeat dose 15 mg/kg ozanezumab) showed a weak, positive anti-ozanezumab-antibody result. PK results were generally consistent with monoclonal antibody treatments. No apparent treatment effects were observed for functional endpoints or muscle biomarkers. Immunohistochemical staining showed dose-dependent co-localization of ozanezumab with Nogo-A in skeletal muscle. In conclusion, single and repeat dose ozanezumab treatment was well tolerated and demonstrated co-localization at the site of action. These findings support future studies with ozanezumab in ALS.\ud \ud TRIAL REGISTRATION\ud \ud ClinicalTrials.gov NCT00875446 GSK-ClinicalStudyRegister.com GSK ID 111330.

BACKGROUND\ud \ud Amyotrophic lateral sclerosis (ALS) is a primary progressive neurodegenerative disease characterised by neuronal loss of lower motor neurons (in the spinal cord and brainstem) and/or upper motor neurons (in the motor cortex) and subsequent denervation atrophy of skeletal muscle.\ud \ud AIM\ud \ud A comprehensive examination of muscle pathology from a cohort of clinically confirmed ALS patients, including an investigation of inflammation, complement activation, and deposition of abnormal proteins in order to compare them with findings from an age-matched, control group.\ud \ud MATERIAL AND METHODS\ud \ud 31 muscle biopsies from clinically confirmed ALS patients and 20 normal controls underwent a comprehensive protocol of histochemical and immunohistochemical stains, including HLA-ABC, C5b-9, p62, and TDP-43.\ud \ud RESULTS\ud \ud Neurogenic changes were confirmed in 30/31 ALS cases. In one case, no neurogenic changes could be detected. Muscle fibre necrosis was seen in 5/31 cases and chronic mononuclear inflammatory cell infiltration in 5/31 (2 of them overlapped with those showing muscle necrosis). In four biopsies there was an increase in the proportion of cytochrome oxidase (COX) negative fibres (2-3%). p62 faintly stained cytoplasmic bodies in eight cases and none were immunoreactive to TDP-43.\ud \ud CONCLUSION\ud \ud This large series of muscle biopsies from patients with ALS demonstrates neurogenic atrophy is a nearly uniform finding and that mild mitochondrial abnormalities and low-grade inflammation can be seen and do not rule out the diagnosis of ALS. These findings could lend support to the notion that ALS is a complex and heterogeneous disorder.

Both growth and survival of motor neurons may depend on multiple neurotrophic factors. Individually, insulin-like growth factor I (IGF-I) and glial cell line-derived neurotrophic factor (GDNF) are potent neurotrophic/survival factors for postnatal motor neurons.We used an organotypic spinal cord model of glutamatergic degeneration in ALS to investigate whether IGF-I and GDNF interact to enhance motor neuron survival, their trophic effect on choline acetyltransferase (ChAT) activity, and their effect on neurite outgrowth.We show that the combination of IGF-I and GDNF at active doses (1) is additively neuroprotective, (2) completely rescues rat motor neurons from chronic glutamate-mediated toxicity, and (3) additively upregulates motor neuron ChAT activity. Further, IGF-I, which by itself does not promote neurite outgrowth in this model, potentiates the neurite promoting action of GDNF.The results predict that IGF-I combined with GDNF may provide a better therapy for the treatment of motor neuron disorders such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy.

Many neurotrophic factors have been shown to enhance survival of embryonic motor neurons or affect their response to injury. Few studies have investigated the potential effects of neurotrophic factors on more mature motor neurons that might be relevant for neurodegenerative diseases. Using organotypic spinal cord cultures from postnatal rats, we have demonstrated that insulin-like growth factor-I (IGF-I) and glial-derived neurotrophic factor (GDNF) significantly increase choline acetyltransferase (ChAT) activity, but brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4/5), and neurotrophin-3 (NT-3) do not. Surprisingly, ciliary neurotrophic factor (CNTF) actually reduces ChAT activity compared to age-matched control cultures. Neurotrophic factors have also been shown to alter the sensitivity of some neurons to glutamate neurotoxicity, a postulated mechanism of injury in the neurodegenerative disease, amyotrophic lateral sclerosis (ALS). Incubation of organotypic spinal cord cultures in the presence of the glutamate transport inhibitor threo-hydroxyaspartate (THA) reproducibly causes death of motor neurons which is glutamate-mediated. In this model of motor neuron degeneration, IGF-I, GDNF, and NT-4/5 are potently neuroprotective, but BDNF, CNTF, and NT-3 are not. The organotypic glutamate toxicity model appears to be the best preclinical predictor to date of success in human clinical trials in ALS.

Peripheral neuropathy has been reported in association with chronic liver disease. However, the precise incidence, severity and characteristics of neuropathy, and the relationship of neuropathy to different etiologies of liver disease have not been defined. In this study, 58 patients with advanced liver disease were evaluated in detail for the presence of neuropathy. Peripheral (sensorimotor) neuropathy was found in 71% and autonomic neuropathy was found in 48% of the patients. Although the majority of patients were asymptomatic, neurological examination showed distal sensory loss to pain, or vibration or distal loss of reflexes in 17 patients (29%). Sensory neuropathy was seen more commonly than motor axonal polyneuropathy on nerve conduction studies. Quantitative sensory testing was frequently abnormal (62%) and cooling thresholds were more affected than vibration thresholds. Overall, the pattern of neuropathy in patients with liver disease conformed to the pattern expected in "dying back" or length-dependent neuropathy. The neuropathy was most severe in patients with advanced hepatic decompensation. Comparison of causes of liver disease showed no significant differences in the severity of neuropathy among the different etiologies. In conclusion, axonal sensory-motor polyneuropathy and autonomic neuropathy are commonly seen in patients with end-stage liver disease of different causes.

Myositis and myasthenia gravis (MG) are both autoimmune disorders presenting with muscle weakness. Rarely, they occur simultaneously in the same patient. Since the management of myasthenia gravis differs from that of myositis, it is important to recognize when patients have both diseases. We reviewed the cases of 6 patients with both myositis and MG to identify clinical features that suggest the possibility of co-existing MG in myositis patients.We identified 6 patients with dermatomyositis or polymyositis and MG. We reviewed their medical records to assess their clinical presentations, laboratory findings, and electrophysiological features.All 6 patients had definite dermatomyositis or polymyositis by the criteria of Bohan and Peter as well as electrophysiologic and/or serologic confirmation of MG. Among overlap patients, 5/6 (83%) had bulbar weakness, 2/6 (33%) had ptosis, and 1/6 (17%) had diplopia. Fatigable weakness was noted by 5/6 (83%) patients. Treatment with pyridostigmine improved symptoms in 5/6 (83%) patients. High-dose steroids were associated with worsening weakness in 2/6 (33%) patients.Prominent bulbar symptoms, ptosis, diplopia, and fatigable weakness should suggest the possibility of MG in patients with myositis. A suspicion of MG may be confirmed through appropriate electrophysiologic and laboratory testing. In those with myositis-MG overlap, high-dose steroids may exacerbate symptoms and pyridostigmine may play an important therapeutic role.

ObjectivesTo study muscle biopsy tissue from patients with juvenile dermatomyositis (JDM) in order to test the reliability of a score tool designed to quantify the severity of histological abnormalities when applied to biceps humeri in addition to quadriceps femoris. Additionally, to evaluate whether elements of the tool correlate with clinical measures of disease severity.Methods55 patients with JDM with muscle biopsy tissue and clinical data available were included. Biopsy samples (33 quadriceps, 22 biceps) were prepared and stained using standardised protocols. A Latin square design was used by the International Juvenile Dermatomyositis Biopsy Consensus Group to score cases using our previously published score tool. Reliability was assessed by intraclass correlation coefficient (ICC) and scorer agreement (α) by assessing variation in scorers’ ratings. Scores from the most reliable tool items correlated with clinical measures of disease activity at the time of biopsy.ResultsInter- and intraobserver agreement was good or high for many tool items, including overall assessment of severity using a Visual Analogue Scale. The tool functioned equally well on biceps and quadriceps samples. A modified tool using the most reliable score items showed good correlation with measures of disease activity.ConclusionsThe JDM biopsy score tool has high inter- and intraobserver agreement and can be used on both biceps and quadriceps muscle tissue. Importantly, the modified tool correlates well with clinical measures of disease activity. We propose that standardised assessment of muscle biopsy tissue should be considered in diagnostic investigation and clinical trials in JDM.

The nosological status of multifocal motor neuropathy remains controversial. The clinical and electrodiagnostic hall-marks suggest selective motor fiber involvement. In this study, we asked to what extent sensory nerves might be involved pathologically in multifocal motor neuropathy. Examination of sensory nerve biopsy specimens from 11 patients did reveal pathological findings in all, but they were very mild. An increased number of thinly myelinated, large-caliber fibers was the unifying feature common to each specimen. By electron microscopy, each biopsy specimen had thinly myelinated fibers surrounded by minor onion bulbs. Active demyelination, though scant, was seen in 3 nerves. Myelinated fiber density was normal. Subperineurial edema and inflammation were not present. We conclude that multifocal motor neuropathy is not an exclusively motor abnormality, although it appears to be so clinically and electrophysiologically. The frequent, albeit mild, pathological abnormalities in sensory fibers suggest that the demyelinating pathophysiology also affects sensory fibers, but to a lesser degree than motor fibers. Some investigators maintain that multifocal motor neuropathy is within the spectrum of chronic inflammatory demyelinating polyneuropathy. The very mild degree of sensory fiber involvement, the absence of inflammation or edema, and the distinctive clinical features support the concept of multifocal motor neuropathy as distinct from chronic inflammatory demyelinating polyneuropathy.

Diagnosis of multifocal motor neuropathy (MMN), a syndrome characterized by progressive asymmetric weakness with intact sensation, is important because the disorder often responds to treatment. Multifocal partial motor conduction block (PMCB) has been emphasized as a cardinal feature in the diagnosis of this syndrome, but detailed nerve conduction studies are not available. Nine patients, ages 28–58, had chronic, progressive, asymmetric, predominantly distal limb weakness for 5–18 years. Sensation was normal and reflexes were reduced asymmetrically. Although all 9 demonstrated PMCB localized to short nerve segments, additional features of multifocal motor demyelination were present, including temporal dispersion (5 patients), segmentally reduced motor nerve conduction velocity (7 patients), prolonged distal motor latency (4 patients), and prolonged F-wave latency (9 patients). The strength of all patients improved after treatment with human immune globulin. A reduction in the degree of PMCB or an increase in the distal motor amplitude or both accompanied the clinical improvement. These studies suggest that patients with MMN demonstrate widespread evidence of motor demyelination in addition to the well-described PMCB, and that reduction of PMCB accounts for the increase in strength following therapy. © 1994 John Wiley & Sons, Inc.

Chronic graft-vs-host disease (cGVHD) myositis is a rare complication of hematopoietic SCT, for which the pathogenesis and optimal therapy are unclear. We performed immunohistochemistry on muscle biopsies from pediatric cGVHD myositis and typical cases of autoimmune dermatomyositis and polymyositis. The immunostaining pattern of cGVHD myositis was distinct from that of typical cases of autoimmunity. There was a high proportion of CD20 + and CD68 + cells, and the best therapeutic response was achieved with rituximab (anti-CD20). These results suggest that cGVHD myositis may be mediated by different leukocytes than similar autoimmune diseases and that treatment may be optimized by targeting the specific cellular infiltrates identified in affected tissue.

Objective: Neuronal nitric oxide synthase (nNOS), normally expressed at the sarcolemmal membrane, is known to be mislocalized to the sarcoplasm in several forms of muscular dystrophy. Our objectives were to characterize further the range of patients manifesting aberrant nNOS sarcolemmal immunolocalization and to study nNOS localization in animal models of nondystrophic myopathy. Methods: We carried out a retrospective cross-sectional study. We performed immunofluorescent staining for nNOS on biopsy specimens from 161 patients with acquired and nondystrophin inherited neuromuscular conditions. The localization of sarcolemmal nNOS correlated with mobility and functional status. Muscle specimens from mouse models of steroid-induced and starvation-related atrophy were studied for qualitative and quantitative nNOS expression. Results: Sarcolemmal nNOS staining was abnormal in 42% of patients with inherited myopathic conditions, 25% with acquired myopathic conditions, 57% with neurogenic conditions, and 93% with hypotonia. Interestingly, we found significant associations between mobility status or muscle function and sarcolemmal nNOS expression. Furthermore, mouse models of catabolic stress also demonstrated mislocalization of sarcolemmal nNOS. Conclusion: Our analyses indicate that nNOS mislocalization is observed in a broad range of nondystrophic neuromuscular conditions associated with impaired mobility status and catabolic stress. Our findings suggest that the assessment of sarcolemmal localization of nNOS represents an important tool for the evaluation of muscle biopsies of patients with a variety of inherited and acquired forms of neuromuscular disorders.

Objective Myofiber necrosis without prominent inflammation is a nonspecific finding in patients with dystrophies and toxic or immune-mediated myopathies. However, the etiology of a necrotizing myopathy is often obscure, and the question of which patients would benefit from immunosuppression remains unanswered. The aim of this study was to identify novel autoantibodies in patients with necrotizing myopathy. Methods Muscle biopsy specimens and serum samples were available for 225 patients with myopathy. Antibody specificities were determined by performing immunoprecipitations from 35S-methionine–labeled HeLa cell lysates. Selected biopsy specimens were stained for membrane attack complex, class I major histocompatibility complex (MHC), and endothelial cell marker CD31. Results Muscle biopsy specimens from 38 of 225 patients showed predominantly myofiber necrosis. Twelve of these patients had a known autoantibody association with or other etiology for their myopathy. Sixteen of the remaining 26 sera immunoprecipitated 200-kd and 100-kd proteins; this specificity was observed in only 1 of 187 patients without necrotizing myopathy. Patients with the anti-200/100 autoantibody specificity had proximal weakness (100%), high creatine kinase levels (mean maximum 10,333 IU/liter), and an irritable myopathy on electromyography (88%). Sixty-three percent of these patients had been exposed to statins prior to the onset of weakness. All patients responded to immunosuppressive therapy, and many experienced a relapse of weakness when the medication was tapered. Immunohistochemical studies showed membrane attack complex on small blood vessels in 6 of 8 patients and on the surface of non-necrotic myofibers in 4 of 8 patients. Five of 8 patients had abnormal capillary morphology, and 4 of 8 patients expressed class I MHC on the surface of non-necrotic myofibers. Conclusion An anti–200/100-kd specificity defines a subgroup of patients with necrotizing myopathy who previously were considered to be autoantibody negative. We propose that these patients have an immune-mediated myopathy that is frequently associated with prior statin use and should be treated with immunosuppressive therapy.

Objective To devise and test a system with which to evaluate abnormalities on muscle biopsy samples obtained from children diagnosed with juvenile dermatomyositis (DM). Methods We established an International Consensus Group on Juvenile DM Biopsy and carried out 2 phases of consensus process and scoring workshops. Biopsy sections (n = 33) were stained by standard methods. The scoring tool was based on 4 domains of change: inflammatory, vascular, muscle fiber, and connective tissue. Using a Latin square design, biopsy samples were scored by 11 experts for items in each domain, and for a global abnormality measure using a 10-cm visual analog score (VAS 0–10). The tool's reliability was assessed using an intraclass correlation coefficient (ICC) and scorer agreement (α) by determining variation in scorers' ratings. Results There was good agreement in many items of the tool, and several items refined between the meetings improved in reliability and/or agreement. The inflammatory and muscle fiber domains had the highest reliability and agreement. The overall VAS score for abnormality had high agreement and reliability, reaching an ICC of 0.863 at the second consensus meeting. Conclusion We propose a provisional scoring system to measure abnormalities on muscle biopsy samples obtained from children with juvenile DM. This system needs to be validated, and then could be used in prospective studies to test which features of muscle pathology are prognostic of disease course or outcome. We suggest that the process we used could be a template for developing similar systems in other forms of myositis.

Background A 17-year-old pregnant woman presented to hospital at 19 weeks' gestation with an 8-week history of hyperemesis gravidarum, 16.8 kg of weight loss, and new-onset weakness, dizziness and blurred vision. Examination of the patient showed confusion, papilledema, ophthalmoparesis, nystagmus, reduced hearing and truncal ataxia. Investigations Physical examination, abdominal ultrasound, fetal ultrasound, brain MRI, magnetic resonance angiography, magnetic resonance venography and cerebrospinal-fluid analysis. Diagnosis Wernicke's encephalopathy, hyperemesis gravidarum and fetal loss. Management Intravenous thiamine repletion and elimination of deficiency risk factors.

Unique autoantibody specificities are strongly associated with distinct clinical phenotypes, making autoantibodies useful for diagnosis and prognosis. To investigate the mechanisms underlying this striking association, we examined autoantigen expression in normal muscle and in muscle from patients with autoimmune myositis. Although myositis autoantigens are expressed at very low levels in control muscle, they are found at high levels in myositis muscle. Furthermore, increased autoantigen expression correlates with differentiation state, such that myositis autoantigen expression is increased in cells that have features of regenerating muscle cells. Consistent with this, we found that cultured myoblasts express high levels of autoantigens, which are strikingly down-regulated as cells differentiate into myotubes in vitro. These data strongly implicate regenerating muscle cells rather than mature myotubes as the source of ongoing antigen supply in autoimmune myositis. Myositis autoantigen expression is also markedly increased in several cancers known to be associated with autoimmune myositis, but not in their related normal tissues, demonstrating that tumor cells and undifferentiated myoblasts are antigenically similar. We propose that in cancer-associated myositis, an autoimmune response directed against cancer cross-reacts with regenerating muscle cells, enabling a feed-forward loop of tissue damage and antigen selection. Regulating pathways of antigen expression may provide unrecognized therapeutic opportunities in autoimmune diseases.

Glutamate toxicity is implicated in the pathogenesis of amyotrophic lateral sclerosis. The neuropeptide N-acetyl-aspartyl glutamate (NAAG) appears to function both as a storage form for glutamate and as a neuromodulator at glutamatergic synapses. N-acetylated-alpha-linked acidic dipeptidase (NAALADase; also termed glutamate carboxypeptidase II) yields N-acetyl aspartate (NAA) and glutamate. Prior studies have demonstrated NAALADase upregulation in motor cortex and increased NAAG, NAA and glutamate in cerebrospinal fluid from amyotrophic lateral sclerosis patients. The potent NAALADase inhibitor, 2-(phosphonomethyl)-pentanedioic acid (2-PMPA), was tested in an in vitro model of chronic glutamate-mediated motor neuron degeneration. Neuroprotection was determined (1) biochemically, by measuring choline acetyltransferase activity, (2) immunohistochemically, by counting neurofilament-H-positive motor neurons and (3) morphologically, with phase contrast microscopy. 2-PMPA (10 microM) had significant neuroprotective effects on motor neurons as evidenced by increased choline acetyltransferase activity, decreased motor neuron loss and improved gross morphology. Results suggest that NAALADase inhibitors protect against chronic glutamate-mediated motor neuron degeneration and may prove therapeutic towards amyotrophic lateral sclerosis.

Partial motor conduction block, an electrophysiological hallmark of demyelination, helps to identify acquired demyelinating neuropathies but its electrophysiological detection can be difficult. We report a technique that may be helpful in this regard. Twenty-five patients with partial motor conduction block secondary to acquired demyelinating polyneuropathy (ADP), 7 with amyotrophic lateral sclerosis (ALS), 7 with stroke, and 11 control subjects, were studied. Amplitude of compound muscle action potentials was recorded after distal electrical (E) stimulation and for volitionally (V) induced responses in 82 muscles. Mean ± SD V/E ratio was 12.3 ± 6.6 for ADP patients, 58.1 ± 17 for ALS patients, 11.4 ± 9 for stroke patients, and 55.4 ± 12.3 for controls. The V/E ratios for patients with partial motor conduction block and stroke were significantly reduced compared with ALS patients and healthy controls (P < 0.05). Surface electromyographic (EMG) recording for determination of the V/E ratio may be a useful technique for detection of a proximal conduction block if a central lesion or poor effort can be excluded. Further study of this novel technique is necessary. Muscle Nerve 27: 590–594, 2003

Background: Thalidomide is effective for the treatment of some refractory dermatologic and oncologic diseases. Toxic neuropathy limits its use, as embryopathy can be avoided by contraceptive measures. Objective: To describe the clinical, electrophysiologic, and pathologic features of thalidomide-induced peripheral neuropathy. Methods: Clinical and electrophysiologic examinations were performed in seven patients with thalidomide-induced peripheral neuropathy. Thalidomide was used for graft-vs-host disease, pyoderma gangrenosum, and discoid lupus with dosages ranging from 100 to 1,200 mg/day for 5 to 16 months (cumulative dosages of 24 to 384 g). Results: All seven patients had clinical and electrophysiologic evidence of a sensory more than motor, axonal, length-dependent polyneuropathy that presented as painful paresthesias or numbness. Sural nerve biopsies, done in three patients, showed evidence of Wallerian degeneration and loss of myelinated fibers. The symptoms, signs, and electrophysiologic data correlated with total cumulative dose of thalidomide. Conclusions: Thalidomide induces a dose-dependent sensorimotor length-dependent axonal neuropathy; it should be judiciously used with close neurologic monitoring.

Background Autoantibodies in the inflammatory myopathies identify unique subsets of patients with distinctive clinical features and provide useful diagnostic and prognostic information. However the association of individual autoantibodies with specific muscle biopsy features has rarely been studied. Objectives To characterize muscle biopsy features associated with different autoantibodies in a cohort of patients with inflammatory myopathies from a single-center. Methods Patients from the Johns Hopkins Myositis Center cohort diagnosed with probable or definite dermatomyositis (according to Bohan and Peter criteria) who had both a muscle biopsy read at Johns Hopkins and a known myositis autoantibody were included in the study. For each biopsy, the presence/absence of the following features were recorded: perifascicular atrophy, mitochondrial dysfunction (>5 COX negative fibers), perivascular inflammation, primary inflammation (invasion of non-necrotic fibers by mononuclear cells) and necrotizing myopathy (defined as biopsies with necrosis/degeneration without perifascicular atrophy or primary inflammation). As a complementary analysis, biopsy features of all anti-Jo1 positive patients with either dermatomyositis or polymyositis were compared through Fisher9s exact test. Results 37 patients with dermatomyositis were included in the study (79.5% definite). These included 11 with anti-Jo-1, 7 with anti-Mi-2, 11 with anti-TIF1-γ, 8 with anti-NXP2, and 5 with anti-PM-Scl. Biopsies from anti-Mi-2 positive patients showed frequent perifascicular atrophy (71.4%), perivascular inflammation (85.7%) and primary inflammation (57.1%); biopsies from anti-TIF1-γ positive patients showed frequent perifascicular atrophy (63.3%), mitochondrial dysfunction (55.6%) and perivascular inflammation (72.7%); biopsies from anti-NXP2 positive patients showed frequent perifascicular atrophy (50%) and biopsies from anti-PM-Scl positive patients showed frequent perivascular inflammation (80%) and primary inflammation (60%). Overall, 16.2% of DM patients had a necrotizing myopathy without perifascicular atrophy or primary inflammation. In the complementary analysis 7 Jo-1 polymyositis patients were identified. Biopsy features of anti-Jo1 patients with dermatomyositis and polymyositis were not statistically different (all p>0.05). Conclusions The majority of anti-PM-Scl and anti-Mi-2 patients have primary inflammation, previously considered the hallmark of PM. Most biopsies from anti-TIF1-γ positive patients reveal mitochondrial dysfunction. 16.2% of DM biopsies have necrotizing myopathy. Biopsy features are similar between dermatomyositis and polymyositis in anti-Jo1 positive patients. References Dalakas MC. Muscle biopsy findings in inflammatory myopathies. Rheumatic diseases clinics of North America 2002;28:779-98, vi. Mozaffar T, Pestronk A. Myopathy with anti-Jo-1 antibodies: pathology in perimysium and neighbouring muscle fibres. Journal of neurology, neurosurgery, and psychiatry 2000;68:472-8. Pestronk A. Acquired immune and inflammatory myopathies: pathologic classification. Current opinion in rheumatology 2011;23:595-604. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.5508

Although pigment epithelium-derived factor (PEDF) is a neurotrophic factor that may aid the development, differentiation, and survival of adjacent neural retinae, the wider distribution of PEDF mRNA in the central nervous system suggested to us that this factor could have pleiotropic neurotrophic and neuroprotective effects on nonretinal neurons. We examined the distribution of PEDF mRNA and its transcript in the spinal cord. By immunohistochemistry and western blot analysis using an antihuman PEDF antiserum of known specificity, we found that PEDF protein is present in spinal cord, cerebrospinal fluid, and skeletal muscle and that its mRNA appears concentrated in motor neurons of the human spinal cord. These observations indicate that PEDF could have potential autocrine and paracrine effects on motor neurons, as well as being target-derived. We analyzed the pharmacologic utility of PEDF in a postnatal organotypic culture model of motor neuron degeneration and proved it is highly neuroprotective. The effect was biologically important, significantly sparing the spinal cord's gross organotypic morphological appearance and preserving motor neuron choline acetyltransferase (ChAT). PEDF alone did not increase ChAT, indicating that the observed effect is neuroprotective, not merely an upregulation of motor neuron ChAT. Further, PEDF preserved motor neuron number, proving a survival effect. We hypothesize that PEDF may play important roles in the survival and maintenance of spinal motor neurons in their neuroprotection against acquired insults in postnatal life. It should be developed further as a therapeutic strategy for motor neuron diseases such as amyotrophic lateral sclerosis (ALS).