Clinical utility of anti-cytosolic 5'-nucleotidase 1A antibody in idiopathic inflammatory myopathies.

OBJECTIVE: To define the clinicopathologic features and diagnostic utility associated with anti-cytosolic 5'-nucleotidase 1A (NT5C1A) antibody seropositivity in idiopathic inflammatory myopathies (IIMs). METHODS: Anti-NT5C1A antibody status was clinically tested between 2014 and 2019 in the Washington University neuromuscular clinical laboratory. Using clinicopathologic information available for 593 patients, we classified them as inclusion body myositis (IBM), dermatomyositis, antisynthetase syndrome, immune-mediated necrotizing myopathy (IMNM), nonspecific myositis, or noninflammatory muscle diseases. RESULTS: Of 593 patients, anti-NT5C1A antibody was found in 159/249 (64%) IBM, 11/53 (21%) dermatomyositis, 7/27 (26%) antisynthetase syndrome, 9/76 (12%) IMNM, 20/84 (24%) nonspecific myositis, and 6/104 (6%) noninflammatory muscle diseases patients. Among patients with IBM, anti-NT5C1A antibody seropositive patients had more cytochrome oxidase-negative fibers compared with anti-NT5C1A antibody seronegative patients. Among 14 IBM patients initially negative for anti-NT5C1A antibody, three patients (21%) converted to positive. Anti-NT5C1A antibody seropositivity did not correlate with malignancy, interstitial lung disease, response to treatments in dermatomyositis, antisynthetase syndrome, and IMNM, or survival in IIMs. INTERPRETATION: Anti-NT5C1A antibody is associated with IBM. However, the seropositivity can also be seen in non-IBM IIMs and it does not correlate with any prognostic factors or survival.

HLA-DRB1 allele and autoantibody profiles in Japanese patients with inclusion body myositis.

INTRODUCTION: Inclusion body myositis (IBM) is an idiopathic inflammatory myopathy, characterized by unique clinical features including finger flexor and quadriceps muscle weakness and a lack of any reliable treatment. The human leukocyte antigen (HLA)-DRB1 allele and autoantibody profiles in Japanese IBM patients have not been fully elucidated. METHODS: We studied 83 Japanese IBM patients with a mean age of 69 years (49 males and 34 females) who participated in the 'Integrated Diagnosis Project for Inflammatory Myopathies' from January 2011 to September 2016. IBM was diagnosed by histological diagnosis. Various autoantibodies were screened by RNA immunoprecipitation and enzyme-linked immunosorbent assays. HLA-DRB1 genotyping was performed using polymerase chain reaction-sequence based typing. A total of 460 unrelated healthy Japanese controls were also studied. RESULTS: The allele frequencies of DRB1*01:01, DRB1*04:10, and DRB1*15:02 were significantly higher in the IBM group than in the healthy control group (Corrected P = 0.00078, 0.00038 and 0.0046). There was a weak association between the DRB1*01:01 allele and severe leg muscle weakness and muscle atrophy. While hepatitis type C virus infection and autoantibodies to cytosolic 5'-nucleotidase 1A were found in 18 and 28 patients, respectively, no significant association with HLA-DRB1 alleles was observed. CONCLUSION: Japanese IBM patients had the specific HLA-DRB1 allele and autoantibody profiles.

Positive Cytosolic 5-Nucleotidase 1A Antibodies in Motor Neuron Disease.

Inclusion body myositis (IBM) is the most common acquired myopathy in adults older than 50 years. Muscle biopsy remains the gold standard for diagnosis. Recently described serum antibodies against cytosolic 5-nucleotidase 1A (cN1A) are considered highly specific for IBM. However, positive cN1A antibodies in diseases other than IBM are recently reported. We review 2 cases in which serum antibodies were positive but ancillary testing revealed motor neuron disease. A 68-year-old man presented with asymmetric quadriceps and handgrip weakness prompting concern for IBM. However, electromyography showed purely chronic neurogenic abnormalities, and muscle biopsy was consistent with post-polio syndrome. A 60-year-old woman reported a history of progressive muscle weakness. Despite positive antibodies, examination and electromyography were indicative of amyotrophic lateral sclerosis. Serum cN1A antibodies are not 100% specific for the diagnosis of IBM. Careful clinical, electrophysiologic, and histopathologic correlation is required in workup of individuals with neuromuscular weakness and positive antibodies.

Inflammatory Myopathies: Utility of Antibody Testing.

Inflammatory myopathies are a group of immune-mediated muscle disorders comprising dermatomyositis; polymyositis; overlap myositis, including antisynthetase syndromes and nonspecific myositis, immune-mediated necrotizing myopathies, and sporadic inclusion body myositis. They are now much more eloquently classified both pathologically and clinically because of the discovery of several myositis-specific and myositis-associated antibodies. These antibodies also aid in choosing the best treatment options in each case. Based on the initial classifications of inflammatory myopathies, inclusion body myositis, overlap myositis, and necrotizing myositis were all included in the polymyositis group. This article discusses cases, diagnostic tools, associated antibodies, and pathology.

Diffusion-weighted magnetic resonance imaging is useful for assessing inflammatory myopathies.

INTRODUCTION: Short tau inversion recovery (STIR) sequences in whole-body MRI are usually used for detecting muscle edema (ME) in inflammatory myopathies. We evaluated b-value 800 diffusion-weighted imaging (b800 DWI). METHODS: Two radiologists independently and a consensus reader retrospectively reexamined 60 patients with inflammatory myopathies and 15 controls. For each participant, 78 muscles were analyzed with 3 sets of imaging acquisitions: T1-weighted (T1) turbo spin echo and STIR; T1 and DWI; and T1, STIR and DWI. Mean edema per patient was compared between sequences. Agreement was evaluated. RESULTS: Diffusion-weighted imaging detected more ME compared with STIR (P < 0.001). Agreement between readers was better with both sequences (k = 0.94) than with b800 DWI (k = 0.89) or STIR (k = 0.84) alone. DISCUSSION: Diffusion-weighted imaging is a valuable add-on for the study of inflammatory myopathies. Muscle Nerve 59:555-555, 2019.

Cytokine Profiling of Serum Allows Monitoring of Disease Progression in Inclusion Body Myositis.

BACKGROUND: Inclusion body myositis is a late onset inflammatory myopathy lacking reliable serum biomarkers for diagnosis and for disease progression. OBJECTIVE: To identify diagnostic and predictive biomarkers, cytokine profiling is used to assess the potential of cytokines to discriminate between cases and controls and to assess whether treatment with methotrexate can influence biomarkers associated with disease progression. METHODS: The diagnostic and follow-up potential of 48 cytokines was tested using Bioplex-assay and ELISA in sera of healthy individuals, IBM patients and patients with other neuromuscular disorders. RESULTS: Ten cytokines (TRAIL, IL-8, MIF, MCP-1, LIF, IP-10, IFN-α2, MIG, bNGF and IL-3) were identified to be good to excellent markers to discern IBM patients from healthy controls. Three cytokines (IP-10, Eotaxin and SDF1A) changed significantly upon methotrexate treatment as compared with the natural clinical course. Muscle strength loss was associated with changes in IL-8 and SDF1A levels. IFN-γ levels were only associated with survival of IBM patients before correction for multiple comparisons. DISCUSSION: Cytokine profiling can discriminate IBM patients from healthy controls and other neuromuscular disorders. Immunosuppression with methotrexate affects cytokine levels in IBM. IL-8 and SDF1A could serve as biomarkers for disease progression.

Overlapping features of polymyositis and inclusion body myositis in HIV-infected patients.

OBJECTIVE: To characterize patients with myositis with HIV infection. METHODS: All HIV-positive patients with myositis seen at the Johns Hopkins Myositis Center from 2003 to 2013 were included in this case series. Muscle biopsy features, weakness pattern, serum creatine kinase (CK) level, and anti-nucleotidase 1A (NT5C1A) status of HIV-positive patients with myositis were assessed. RESULTS: Eleven of 1,562 (0.7%) patients with myositis were HIV-positive. Myositis was the presenting feature of HIV infection in 3 patients. Eight of 11 patients had weakness onset at age 45 years or less. The mean time from the onset of weakness to the diagnosis of myositis was 3.6 years (SD 3.2 years). The mean of the highest measured CK levels was 2,796 IU/L (SD 1,592 IU/L). On muscle biopsy, 9 of 10 (90%) had endomysial inflammation, 7 of 10 (70%) had rimmed vacuoles, and none had perifascicular atrophy. Seven of 11 (64%) patients were anti-NT5C1A-positive. Upon presentation, all had proximal and distal weakness. Five of 6 (83%) patients followed 1 year or longer on immunosuppressive therapy had improved proximal muscle strength. However, each eventually developed weakness primarily affecting wrist flexors, finger flexors, knee extensors, or ankle dorsiflexors. CONCLUSIONS: HIV-positive patients with myositis may present with some characteristic polymyositis features including young age at onset, very high CK levels, or proximal weakness that improves with treatment. However, all HIV-positive patients with myositis eventually develop features most consistent with inclusion body myositis, including finger and wrist flexor weakness, rimmed vacuoles on biopsy, or anti-NT5C1A autoantibodies.

A Case of Asymptomatic Inclusion Body Myositis.

OBJECTIVES: To present a case of asymptomatic inclusion body myositis. METHODS: The authors report a case of a 67-year-old man who presented with idiopathic hyperCKemia. Physical examination including a complete neurological evaluation was unremarkable. Systemic causes of hyperCKemia, including medication side effects, metabolic and endocrine disorders, and connective tissue disorders, were ruled out with various indicated tests. RESULTS: Two and a half years after initial consultation, the patient reported left knee pain. Magnetic resonance imaging of the left knee showed edema in the mid and distal aspect of the vastus medialis and vastus lateralis muscles. A biopsy of the left quadriceps muscles was diagnostic of inclusion body myositis. He remained asymptomatic for the ensuing 2.5 years. CONCLUSIONS: Asymptomatic hyperCKemia should be investigated and followed closely for definitive diagnosis and possible treatable causes.

Cytosolic 5'-nucleotidase 1A autoantibody profile and clinical characteristics in inclusion body myositis.

OBJECTIVES: Autoantibodies directed against cytosolic 5'-nucleotidase 1A have been identified in many patients with inclusion body myositis. This retrospective study investigated the association between anticytosolic 5'-nucleotidase 1A antibody status and clinical, serological and histopathological features to explore the utility of this antibody to identify inclusion body myositis subgroups and to predict prognosis. MATERIALS AND METHODS: Data from various European inclusion body myositis registries were pooled. Anticytosolic 5'-nucleotidase 1A status was determined by an established ELISA technique. Cases were stratified according to antibody status and comparisons made. Survival and mobility aid requirement analyses were performed using Kaplan-Meier curves and Cox proportional hazards regression. RESULTS: Data from 311 patients were available for analysis; 102 (33%) had anticytosolic 5'-nucleotidase 1A antibodies. Antibody-positive patients had a higher adjusted mortality risk (HR 1.89, 95% CI 1.11 to 3.21, p=0.019), lower frequency of proximal upper limb weakness at disease onset (8% vs 23%, adjusted OR 0.29, 95% CI 0.12 to 0.68, p=0.005) and an increased prevalence of excess of cytochrome oxidase deficient fibres on muscle biopsy analysis (87% vs 72%, adjusted OR 2.80, 95% CI 1.17 to 6.66, p=0.020), compared with antibody-negative patients. INTERPRETATION: Differences were observed in clinical and histopathological features between anticytosolic 5'-nucleotidase 1A antibody positive and negative patients with inclusion body myositis, and antibody-positive patients had a higher adjusted mortality risk. Stratification of inclusion body myositis by anticytosolic 5'-nucleotidase 1A antibody status may be useful, potentially highlighting a distinct inclusion body myositis subtype with a more severe phenotype.

Comparison of Serum rAAV Serotype-Specific Antibodies in Patients with Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, Inclusion Body Myositis, or GNE Myopathy.

Recombinant adeno-associated virus (rAAV) is a commonly used gene therapy vector for the delivery of therapeutic transgenes in a variety of human diseases, but pre-existing serum antibodies to viral capsid proteins can greatly inhibit rAAV transduction of tissues. Serum was assayed from patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), inclusion body myositis (IBM), and GNE myopathy (GNE). These were compared to serum from otherwise normal human subjects to determine the extent of pre-existing serum antibodies to rAAVrh74, rAAV1, rAAV2, rAAV6, rAAV8, and rAAV9. In almost all cases, patients with measurable titers to one rAAV serotype showed titers to all other serotypes tested, with average titers to rAAV2 being highest in all instances. Twenty-six percent of all young normal subjects (<18 years old) had measurable rAAV titers to all serotypes tested, and this percentage increased to almost 50% in adult normal subjects (>18 years old). Fifty percent of all IBM and GNE patients also had antibody titers to all rAAV serotypes, while only 18% of DMD and 0% of BMD patients did. In addition, serum-naïve macaques treated systemically with rAAVrh74 could develop cross-reactive antibodies to all other serotypes tested at 24 weeks post treatment. These data demonstrate that most DMD and BMD patients should be amenable to vascular rAAV-mediated treatment without the concern of treatment blockage by pre-existing serum rAAV antibodies, and that serum antibodies to rAAVrh74 are no more common than those for rAAV6, rAAV8, or rAAV9.

N-terminal α Dystroglycan (αDG-N): A Potential Serum Biomarker for Duchenne Muscular Dystrophy.

BACKGROUND: Duchenne Muscular Dystrophy (DMD) is a severe, progressive, neuromuscular disorder of childhood. While a number of serum factors have been identified as potential biomarkers of DMD, none, as yet, are proteins within the dystrophin-associated glycoprotein (DAG) complex. OBJECTIVE: We have developed an immobilized serum ELISA assay to measure the expression of a constitutively cleaved and secreted component of the DAG complex, the N-terminal domain of α dystroglycan (αDG-N), and assayed relative expression in serum from muscular dystrophy patients and normal controls. METHODS: ELISAs of immobilized patient or mouse serum and Western blots were used to assess αDG-N expression. RESULTS: Immobilization of diluted serum on ELISA plates was important for this assay, as methods to measure serum αDG-N in solution were less robust. αDG-N ELISA signals were significantly reduced in DMD serum (27±3% decrease, n = 9, p < 0.001) relative to serum from otherwise normal controls (n = 38), and calculated serum αDG-N concentrations were reduced in DMD relative to normal (p < 0.01) and Becker Muscular Dystrophy (n = 11, p < 0.05) patient serum. By contrast, ELISA signals from patients with Inclusion Body Myositis were not different than normal (4±3% decrease, n = 8, p = 0.99). αDG-N serum signals were also significantly reduced in utrophin-deficient mdx mice as compared to mdx and wild type mice. CONCLUSIONS: Our results are the first demonstration of a component of the DAG complex as a potential serum biomarker in DMD. Such a serum measure could be further developed as a tool to help reflect overall muscle DAG complex expression or stability.

Advances in serological diagnostics of inflammatory myopathies.

PURPOSE OF REVIEW: Inflammatory myopathies are rare diseases. Their diagnosis criteria are historically based on their clinical phenotype (topography of the muscle weakness, presence of skin lesions and/or of extra-skin/muscle signs) and the presence of inflammatory infiltrates on muscle biopsy. However, the recent discovery of different myositis-specific antibodies (MSA) or myositis-associated antibodies (MAA) permitted to revisit these old classifications. This review covers recent findings in clinical and pathological phenotypes regarding prognosis, associated cancer and response to the treatment based on MSA/MAA categorization. RECENT FINDINGS: Since the mid-1970s, about 20 MSA or MAA were discovered year after year (by immunoprecipitation). Now commercial kits (mainly dot line assays) permit their detection routinely which is clearly a help for the diagnosis but also give some key indications on clinical features, risk of associated cancers and response to the treatments. SUMMARY: Overlap myositis is associated with antisynthetase antibodies (Abs) or those associated with sclerodermia (anti-RNP, Ku and PM-ScL). Dermatomyositis is associated with anti-Mi2, small ubiquitin-like modifier activating enzyme (SAE), nuclear matrix protein-2 (NXP2), TIF-1γ or melanoma differentiation-associated gene 5 (MDA5) Abs. Immune-mediated necrotizing myopathies are associated with anti-signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) Abs. One third of inclusion body myositis' patients also presented anti-cytosolic 5'-nucleotidase 1A (cN1A) Abs. The risk of associated cancers is elevated with anti-TIF-1γ, NXP2 or HMGCR Abs.

Sporadic inclusion body myositis: A review of recent clinical advances and current approaches to diagnosis and treatment.

Sporadic inclusion body myositis is the most frequent acquired myopathy of middle and later life and is distinguished from other inflammatory myopathies by its selective pattern of muscle involvement and slowly progressive course, and by the combination of inflammatory and degenerative muscle pathology and multi-protein deposits in muscle tissue. This review summarises the findings of recent studies that provide a more complete picture of the clinical phenotype and natural history of the disease and its global prevalence and genetic predisposition. Current diagnostic criteria, including the role of electrophysiological and muscle imaging studies and the recently identified anti-5'-nucleotidase (anti-cN1A) antibody in diagnosis are also discussed as well as current trends in the treatment of the disease.

Novel serology testing for sporadic inclusion body myositis: disease-specificity and diagnostic utility.

PURPOSE OF REVIEW: The purpose of this article is to discuss recent advances in serological testing for sporadic inclusion body myositis (sIBM) and to provide a review of their diagnostic utility and disease-specificity of auto-antibodies in sIBM. RECENT FINDINGS: The identification, prevalence and diagnostic utility of a new auto-antibody targeting cytosolic 5'-nucleotidase 1A (cN-1A) in the serum of sIBM patients have recently been published. These studies have shown that anti-cN-1A auto-antibodies have diagnostic utility for differentiating sIBM from other forms of myositis and from other neuromuscular diseases. Anti-cN-1A-positive patient sera are directed to multiple epitopes of cN-1A and contain, in addition to IgG, IgA and IgM, anti-cN-1A auto-antibodies. Recent studies have also shown a relatively high prevalence of these auto-antibodies in sera form Sjögren's syndrome and systemic lupus erythematosus patients. SUMMARY: The recent discovery of auto-antibodies to cN-1A provides a serological tool to aid the differentiation between inflammatory myopathies and supports the idea that apart from degeneration, an adaptive immune response may also play a role in sIBM pathophysiology. Future research will need to focus on standardization of methods to detect these auto-antibodies in order to further explore their specificity and diagnostic utility for sIBM.

A case report comparing clinical, imaging and neuropsychological assessment findings in twins discordant for the VCP p.R155C mutation.

Inclusion body myopathy, Paget disease of bone and/or frontotemporal dementia is an autosomal dominant disease caused by mutations in the Valosin Containing Protein (VCP) gene. We compared clinical findings including MRI images and neuropsychological assessment data in affected and unaffected twin brothers aged 56 years from a family with the p.R155C VCP gene mutation. The affected twin presented with a 10 year history of progressive proximal muscle weakness, difficulty swallowing, gastroesophageal reflux, fecal incontinence, and peripheral neuropathy. Comprehensive neuropsychological testing revealed rapid cognitive decline in the absence of any behavioral changes in a span of 1 year. This case illustrates that frontotemporal dementia related cognitive impairment may precede behavioral changes in VCP disease as compared with predominance of behavioral impairment reported in previous studies. Our findings suggest that there is a need to establish VCP disease specific tools and normative rates of decline to detect pre-clinical cognitive impairment among affected individuals.

Sporadic inclusion body myositis: new insights and potential therapy.

PURPOSE OF THE REVIEW: To describe new insights and developments in the pathogenesis, diagnosis and treatment of sporadic inclusion body myositis (IBM). RECENT FINDINGS: Various hypothesis about the pathogenesis of IBM continue to be investigated, including autoimmune factors, mitochondrial dysfunction, protein dyshomeostasis, altered nucleic acid metabolism, myonuclear degeneration and the role of the myostatin pathway. Serum autoantibodies against cytosolic 5'-nucleotidase 1A have been identified in IBM showing moderate diagnostic performance. The differential diagnostic value of histopathological features, including different protein aggregates, continues to be evaluated. MRI may also be of monitoring value in IBM. New therapeutic strategies are being tested in IBM patients, namely the upregulation of the heat shock response and the antagonism of myostatin. SUMMARY: Recent important advances have occurred in IBM. These advances, including recent and ongoing clinical trials, may lead to earlier diagnosis and improved understanding and treatment of the disease. Despite improved knowledge, IBM continues to be a puzzling disease and the pathogenesis remains to be clarified. An interdisciplinary, bench to bedside translational research approach is crucial for the successful identification of novel treatments for this debilitating, currently untreatable disorder.

Cytoplasmic 5'-nucleotidase autoantibodies in inclusion body myositis: Isotypes and diagnostic utility.

INTRODUCTION: Recent studies have identified circulating immunoglobulin (Ig) G autoantibodies against cytoplasmic 5'-nucleotidase 1A (cN1A; NT5C1A) in patients with inclusion body myositis (IBM), whose detection provides for an IBM blood diagnostic test. Whether or not anti-cN1A autoantibody isotypes other than IgG are present in IBM has not previously been reported. METHODS: Plasma and serum samples from 205 patients (50 with and155 without IBM) were studied for the presence of IgM and IgA, in addition to IgG, anti-cN1A autoantibodies using immunoblots and enzyme-linked immunoassays (ELISAs). RESULTS: IgM, IgA, and IgG anti-cN1A autoantibodies were detected by ELISA with similar sensitivities (49-53%) and specificities (94-96%), but with differing patterns of autoantibody isotype presence. Combination assays of all 3 autoantibody levels improved diagnostic sensitivity to 76%. CONCLUSIONS: In addition to previously recognized IgG anti-cN1A autoantibodies, IBM patients have circulating IgM and IgA anti-cN1A autoantibodies. Differing patterns of these isotypes may be present and useful for diagnosis.