Necrotizing autoimmune myopathy

Plasma Exchange in Anti-Signal Recognition Particle Myopathy: A Systematic Review and Combined Analysis of Patient Individual Data

Anti-signal recognition particle myopathy (anti-SRP myopathy) is a rare subtype of immune-mediated inflammatory myopathy characterized by muscle weakness and anti-SRP autoantibodies. Although plasma exchange (PE) is used in severe cases, its role remains unclear. A systematic review was conducted following PRISMA guidelines, identifying 23 patients with anti-SRP myopathy treated with PE. Data on demographics, clinical features, laboratory findings, treatments, and outcomes were analyzed combining individual patient data if available. Sixteen (69.6%) patients were male, with muscle weakness as the predominant symptom in 100% of cases. After PE, most patients showed improvement in symptoms, and the proportion of patients with muscle weakness was reduced (p = 0.001). Relapse occurred in 17.4% of the cases. The incidence of adverse events was low (8.7%). Despite limitations, including a small sample size and heterogeneous data, our systematic review suggests that PE may be effective in inducing remission and controlling symptoms in anti-SRP myopathy, particularly in severe cases. Since evidence on PE in anti-SRP myopathy is limited, further research, including prospective multicenter studies, is warranted to understand better its efficacy and safety and establish its role in treatment algorithms.

Marked Efficacy of a Therapeutic Strategy in a Patient With Necrotizing Myopathy Associated With Anti-signal Recognition Particle (SRP) Autoantibodies

Necrotizing autoimmune myopathy (NAM) is a rare muscular disorder characterized by severe proximal muscle weakness. Risk factors include statin use, malignancy, and connective tissue diseases. The current study presents the first case of NAM in Saudi Arabia in a 26-year-old female who presented with proximal upper and lower limb weakness, dysphagia, dysarthria, and dyspnea with no previous medical or surgical history and was not on medication. Targeted myopathic antibody analysis revealed antibodies to signal recognition particles (SRP), and the serum creatinine kinase level reached 9308 U/L. A diagnosis of NAM was made, and the patient was started on the management plan. We discussed an interesting case progression and adverse effect challenges, as well as the management of these difficult-to-treat conditions.

Preservation of shortening velocity and power output in single muscle fibres from patients with idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders of skeletal muscle causing weakness and disability. Utilizing single fibre contractility studies, we have previously shown that contractility is affected in muscle fibres from individuals with IIMs. For the current study, we hypothesized that a compensatory increase in shortening velocity occurs in muscle fibres from individuals with IIMs in an effort to maintain power output. We performed in vitro single fibre contractility studies to assess force-velocity relationships and maximum shortening velocity (V_max) of muscle fibres from individuals with IIMs (25 type I and 58 type IIA) and healthy controls (66 type I and 27 type IIA) and calculated maximum power output (W_max) for each fibre. We found significantly higher V_max (mean ± SEM) of fibres from individuals with IIMs, for both type I (1.40 ± 0.31 fibre lengths/s, n = vs. 0.63 ± 0.13 fibre lengths/s; p = 0.0019) and type IIA fibres (2.00 ± 0.17 fibre lengths/s vs 0.77 ± 0.10 fibre lengths/s; p < 0.0001). Furthermore, W_max (mean ± SEM) was maintained compared to fibres from healthy controls, again for both type I and type IIA fibres (4.10 ± 1.00 kN/m²·fibre lengths/s vs. 2.00 ± 0.16 kN/m²·fibre lengths/s; p = ns and 9.00 ± 0.64 kN/m²·fibre lengths/s vs. 6.00 ± 0.67 kN/m²·fibre lengths/s; p = ns respectively). In addition, type I muscle fibres from individuals with IIMs was able to develop maximum power output at lower relative force. The findings of this study suggest that compensatory responses to maintain power output, including increased maximum shortening velocity and improved efficiency, may occur in muscle of individuals with IIMs. The mechanism underlying this response is unclear, and different hypotheses are discussed.

The Evolution of Complex Muscle Cell In Vitro Models to Study Pathomechanisms and Drug Development of Neuromuscular Disease

Many neuromuscular disease entities possess a significant disease burden and therapeutic options remain limited. Innovative human preclinical models may help to uncover relevant disease mechanisms and enhance the translation of therapeutic findings to strengthen neuromuscular disease precision medicine. By concentrating on idiopathic inflammatory muscle disorders, we summarize the recent evolution of the novel in vitro models to study disease mechanisms and therapeutic strategies. A particular focus is laid on the integration and simulation of multicellular interactions of muscle tissue in disease phenotypes in vitro. Finally, the requirements of a neuromuscular disease drug development workflow are discussed with a particular emphasis on cell sources, co-culture systems (including organoids), functionality, and throughput.

Immune-Mediated Myopathy in a Patient Presenting for Melanoma Resection and Sentinel Lymph Node Biopsy

Statin-induced necrotizing autoimmune myopathy (SINAM) is a rare side effect in people who are taking a class of drugs called statins. Patients with SINAM will present with subacute severe symmetric proximal muscle weakness. In contrast to more common myopathies, SINAM may not spontaneously resolve with statin discontinuation. These patients may require long-term immunotherapy to limit further disease progression. In this case study, we report a 74-year-old female with SINAM who presented for radical excision of a right upper back melanoma and sentinel lymph node biopsy at an outpatient facility. An anesthetic plan was crafted with the use of a supraglottic airway device without neuromuscular blockade.

Therapeutic plasma exchange for the treatment of refractory necrotizing autoimmune myopathy

Introduction

Necrotizing autoimmune myopathy (NAM) is strongly associated with pathognomonic autoantibodies targeting 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase (HMGCR) or signal recognition particle (SRP), whose levels in turn are correlated with serum creatine kinase (CK) and necrosis. Thus, NAM may be amenable to therapeutic plasma exchange (TPE) to remove pathogenic antibodies and improve patient symptoms.

Methods

A retrospective case series and literature review of patients presenting with NAM and undergoing treatment with TPE was performed. Clinical data including patient demographics, symptoms, physical exam findings, muscle biopsy, lower extremity imaging, prior therapy, and duration from diagnosis to TPE initiation were collected retrospectively for adult patients with NAM treated with TPE after failing to respond to immunomodulatory therapy. Laboratory data including change in CK levels and myositis‐specific antibody titers from baseline were measured in some patients.

Results

Six patients (median age at diagnosis 52.5 years, interquartile range [IQR] 35.8‐64.5 years, four male/two female) underwent a median of 7.5 (IQR: 5‐10) TPE procedures with 5% albumin as replacement. All patients exhibited a statistically significant reduction in CK level from pre‐TPE baseline (range: 43.0%‐58.7% reduction). Responses in this cohort were best in patients with antibodies targeting HMGCR and SRP, which are most strongly associated with NAM. These results compare favorably to a literature review of NAM patients (n = 19) treated with TPE, who also exhibited positive clinical and laboratory responses across varying treatment lengths.

Conclusion

TPE can play a role in the management of NAM, particularly in patients with HMGCR or SRP antibodies who are refractory to pharmacologic immunosuppression.

Immune-mediated necrotizing myopathy (IMNM): A myopathological challenge

This review is focused on the myopathological spectrum of immune mediated necrotizing myopathies (IMNMs) and its differentiation with other, potentially mimicking, inflammatory and non-inflammatory myopathies. IMNMs are a subgroup of idiopathic inflammatory myopathies (IIMs) characterized by severe clinical presentation with rapidly progressive muscular weakness and creatine kinase elevation, often requiring early aggressive immunotherapy, associated to the presence of muscle specific autoantibodies (MSA) against signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR). Muscle biopsy usually shows unspecific features consisting in prominent necrosis and regeneration of muscle fibres with mild or absent inflammatory infiltrates, inconstant and faint expression of major histocompatibility complex (MHC) class I and variable deposition of C5b-9 on sarcolemma. Several conditions could present similar histopathological findings leading to possible misdiagnosis of IMNM with other IIMs or non-inflammatory myopathies (nIMs) and viceversa. This review analyses the muscle biopsy data in IMNMs through a systematic revision of the literature from the last five decades. Several histopathological variables have been considered in both SRP- and HMGCR-IMNM, and compared to other IIMs - as dermatomyositis (DM) and anti-synthethase syndrome (ASS) - or other nIMs -as toxic myopathies (TM), critical illness myopathy (CIM) and muscular dystrophy (MD) - to elucidate similarities and differences among these potentially mimicking conditions. The major histopathological findings of IMNMs were: very frequent necrosis and regeneration of muscle fibres (93%), mild inflammatory component mainly constituted by scattered isolated (65%) CD68-prevalent (68%) cells, without CD8 invading/surrounding non-necrotic fibres, variable expression of MHC-I in non-necrotic fibres (56%) and constant expression of sarcoplasmic p62, confirming those that are widely considered the major histological characteristics of IMNMs. Conversely, only 42% of biopsies showed a sarcolemmal deposition of C5b-9 component. Few differences between SRP and HMGCR IMNMs consisted in more severe necrosis and regeneration in SRP than in HMGCR (p = 0.01); more frequent inflammatory infiltrates (p = 0.007) with perivascular localization (p = 0.01) and clustered expression of MHC-I (p = 0.007) in HMGCR; very low expression of sarcolemmal C5b-9 in SRP (18%) compared to HMGCR (56%) (p = 0.0001). Milder necrosis and regeneration, detection of perifascicular pathology, presence of lymphocytic inflammatory infiltrates and myofibre expression of MxA help to distinguish DM or ASS from IMNM. nIMs can present signs of inflammation at muscle biopsy. Low fibre size variability with overexpression of both MHC-I and II, associated with C5b-9 deposition, could could be observed in CIM, while increased connective tissue should lead to consider MD, or TM in absence of C5b-9 deposition. Nevertheless, these features are not constantly detected and muscle biopsy could not be diriment. For this reason, muscle biopsy should always be critically considered in light of the clinical context before concluding for a definite diagnosis of IMNM, only based on histopathological findings. More rigorous collection and analysis of muscle biopsy is warranted to obtain a higher quality and more homogeneous histopathological data in inflammatory myopathies.

Prominent Asymmetric Muscle Weakness and Atrophy in Seronegative Immune-Mediated Necrotizing Myopathy

Immune-mediated necrotizing myopathy, a new subgroup of inflammatory myopathies, usually begins with subacute onset of symmetrical proximal muscle weakness. A 35-year-old male presented with severe asymmetric iliopsoas atrophy and low back pain with a previous history of left lower extremity weakness. Although his first left lower extremity weakness occurred 12 years ago, he did not receive a clear diagnosis. Magnetic resonance imaging of both thigh muscles showed muscle edema and contrast enhancement in patch patterns, and the left buttock and thigh muscles were more atrophied compared to the right side. Serum creatine kinase levels were elevated, and serologic testings were all negative. Genetic testing using a targeted gene-sequencing panel for neuromuscular disease including myopathy identified no pathogenic variants. Muscle biopsy on the right vastus lateralis showed scattered myofiber necrosis with phagocytosis and an absence of prominent inflammatory cells, consistent with seronegative necrotizing myopathy. Thus, unusual asymmetric muscle weakness and atrophy can be a manifestation of inflammatory myopathy.

Muscle shear wave elastography, conventional B mode and power doppler ultrasonography in healthy adults and patients with autoimmune inflammatory myopathies: a pilot cross-sectional study

Background

Before the role of shear wave elastography (SWE) and B mode ultrasound (US) in the diagnosis of different forms of idiopathic inflammatory myopathies (IIM) can be investigated, normative data is required. This study aimed to describe and then compare normative SWE and B mode ultrasound metrics of muscles in healthy controls and patients with IIM.

Methods

Twenty nine healthy adult controls and 10 IIM patients (5 with inclusion body myositis and 5 with necrotising autoimmune myopathy) underwent a full clinical examination, laboratory investigations, SWE and US measurements of selected proximal and distal limb muscles. Shear wave speed (SWS) and multiple US domains [echogenicity, fascial thickness, muscle bulk and power Doppler (PD)] were measured in both groups.

Results

In healthy controls (n = 29; mean age 46.60 ± 16.10; 44.8 % female), age was inversely correlated with SWS at the deltoid (stretch) (Rs. -0.40, p = 0.030) and PD score at the deltoid (rest) (Rs. -0.40, P = 0.032). Those ≥ 50 years old had a lower SWS at the deltoid (stretch) compared to the < 50 year group (2.92 m/s vs. 2.40 m/s, P = 0.032). Age correlated with increased echogenicity in the flexor digitorum profundus (Rs. 0.38, P = 0.045). Females had a smaller muscle bulk in the deltoid (P = 0.022). Body mass index (BMI) was inversely associated with SWS in the deltoid (stretch) (Rs – 0.45, P = 0.026), and positively correlated with echogenicity in the deltoid (Rs. 0.69, P = 0.026). In patients ≥50 years of age, patients with IIM (mean age 61.00 ± 8.18; females 20.0 %) had a higher proportion of abnormal echogenicity scores at the flexor digitorum profundus (FDP) (40.00 % vs. 14.30 %, P = 0.022) and tibialis anterior (TA) (80.00 % vs. 28.60 %, P = 0.004). Fascial thickness was lower in the FDP (0.63mm vs. 0.50mm, p = 0.012) and TA (0.58mm vs. 0.45mm, P = 0.001).

Conclusions

Our findings suggest there is scope for US techniques to be useful for diagnostic screening of affected muscles in patients with IIM, especially in those with suspected inclusion body myositis or necrotising autoimmune myopathy. We provide normative data for future studies into SWE and US techniques in skeletal muscle. The differences between IIM patients and controls warrant further study in a broader IIM patient cohort.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04424-0.

Statin-Induced Necrotizing Autoimmune Myositis: Diagnosis and Management

Statins are among the most frequently prescribed drugs as they effectively lower cardiovascular mortality. Atherosclerotic plaques are stabilized and lipid levels are lowered, as statins inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Patients placed on these drugs frequently report muscle aches, but true myositis that would call for discontinuance of the drug is actually uncommon. Workup for statin-induced myositis would require ruling out other causes of myositis and muscular dystrophies, and this can often be perplexing for the primary care physician to whom these patients initially present. This case report and recommendations may serve as a helpful guide.

Asymptomatic necrotizing myositis in a young male with progressive interstitial lung disease

Necrotizing autoimmune myopathy (NAM) is a rare inflammatory process characterized by bilateral proximal muscle weakness and elevated creatinine kinase levels. It is one of the idiopathic inflammatory myopathies. It can be associated with anti-signal recognition particle (SRP) antibody which is commonly seen in middle-aged females. Classic findings on muscle biopsy include muscle fiber necrosis without inflammation. Pulmonary manifestations associated with anti-SRP NAM is rare, and often a challenging correlation to make as our understanding of inflammatory myopathies and interstitial lung disease is still evolving. There have been some associations of Anti SRP NAM with NSIP which responds to corticosteroids. We present a 29 year old male with asymptomatic NAM who presented with a combination of NSIP and pulmonary arterial hypertension (PAH). His PAH was responsive to oral vasodilator therapy however his interstitial lung disease (ILD) rapidly progressed to usual interstitial pneumonia (UIP) requiring lung transplantation. This case highlights 1) an extremely rare presentation of rapidly progressive NAM associated ILD in a young man, in which pulmonary manifestations occurred in the absence of myopathy, 2) The importance of doing a complete work up for interstitial lung disease, including diligent examination for myopathic features and obtaining CK levels, 3) Identifying that interstitial lung diseases can progress despite control of the underlying etiology with corticosteroids and immunosuppressives, 4) Recognition of pre capillary PAH in patients with disproportionally elevated pressures relative to their pulmonary findings, 5) The first report of treatment responsive pulmonary vascular disease associated with NAM, and 6) The importance of early lung transplantation evaluation.

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Creatinine kinase should be checked in all interstitial lung disease evaluation.

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Pulmonary involvement with anti-SRP necrotizing autoimmune myopathy is rare.

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Pulmonary involvement and severity does not correlate with myositis activity.

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Lung transplantation evaluation should be performed early on with rare diseases.

Seronegative necrotizing autoimmune myopathy with favorable response to intravenous immunoglobulin

We describe a 68-year-old man who presented with progressive weakness in proximal muscles of all four limbs and was found to have autoantibody-negative necrotizing autoimmune myopathy (NAM). His myopathy was refractory to corticosteroids and methotrexate, but subsequently demonstrated successful response to intravenous immunoglobulin (IVIG). The patient also received rituximab, but the timing of his recovery favored IVIG as the more important factor in terms of efficacy. Treatment guidelines for seronegative necrotizing myopathies are lacking. This case suggests a potential efficacious treatment option for the seronegative subset of NAM.

An exploratory study of contractile force production in muscle fibers from patients with inflammatory myopathies

INTRODUCTION

The mechanism by which weakness develops in idiopathic inflammatory myopathies (IIMs) is still unclear. In this study we investigated the maximum force of single muscle fibers from patients with IIMs.

METHODS

Permeabilized single muscle fibers from patients with IIMs and healthy controls were subjected to contractility measurements. Maximum force and specific force production (maximum force normalized to fiber size) and fiber type were determined for each isolated fiber.

RESULTS

A total of 178 fibers were studied from five patients with IIMs and 95 fibers from four controls. Specific force production was significantly lower in the IIM group for all fiber types.

DISCUSSION

The findings from this exploratory study suggest that weakness in IIMs may, in part, be caused by dysfunction of the contractile apparatus. These findings provide a basis for further studies into the mechanisms underlying weakness in IIMs.

Statin-induced necrotising autoimmune myopathy and autoimmune hepatitis presenting with dysphagia

Statin-induced necrotising autoimmune myopathy (SINAM) is a rare disease characterised by proximal muscle weakness and elevated creatine kinase levels that is usually in the thousands. Anti-3-hydroxy-3-methyl glutaryl co-enzyme A reductase (HMGCR) antibodies are associated with SINAM. Autoimmune hepatitis (AIH) is an inflammatory disease of the liver that is usually of unknown aetiology but can also be associated with concurrent extrahepatic autoimmune disorders. We are reporting a case of biopsy proven AIH associated with SINAM in a patient presenting with oropharyngeal dysphagia. The patient had elevated anti-HMGCR antibodies and anti-smooth muscle antibodies. SINAM and AIH were confirmed by muscle biopsy and liver biopsy, respectively. The patient had complete resolution of his symptoms and complete normalisation of his liver function tests after 6 months of the treatment.

Anti-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody in necrotizing myopathy: treatment outcomes, cancer risk, and role of autoantibody level

Objective: To evaluate clinical associations of anti-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody (Ab) and statin exposure in necrotizing myopathy (NM) patients. Methods: NM without a known myositis-specific autoantibody (MSA) was ascertained from a large single-centre myositis database between 1985 and 2012. A comparison NM cohort included 32 anti-SRP⁺ autoantibody patients, and other control groups included 74 non-NM myositis patients and 21 non-myositis controls. Sera from all cases and controls were tested using a validated anti-HMGCR enzyme-linked immunosorbent assay. Clinical features including statin use and anti-HMGCR Ab status were compared between cases and controls. Results: Of the 256 NM muscle biopsies reviewed, only 48 subjects with available sera were identified as traditional MSA-negative NM. Anti-HMGCR positivity was significantly (p < 0.001) associated with MSA-negative NM [48% (23/48)] compared to all of the myositis and non-myositis controls [5% (6/127)]. Most anti-HMGCR Ab-positive NM patients had high titres of anti-HMGCR (83%) and a history of statin exposure (78%), along with severe muscle weakness, high creatine kinase (CK) levels (90% ≥ 5000 IU/L), a paucity of other organ manifestations, and the need for immunosuppression with prednisone and methotrexate, but generally favourable outcomes. Anti-HMGCR serum levels were associated with baseline CK levels but not muscle weakness. Conclusion: HMGCR Ab-positive NM patients are associated with statin exposure, have severe muscle weakness and high CK at presentation, lack other organ manifestations, and generally have favourable outcomes from immunosuppression. Anti-HMGCR Abs should be assessed in MSA-negative NM patients, particularly those with a history of statin exposure.

Clinical spectrums and outcomes of necrotizing autoimmune myopathy versus other idiopathic inflammatory myopathies: a multicenter case-control study

OBJECTIVE

To investigate the clinical characteristics, laboratory features, and treatment outcomes of Thai patients compared between those with necrotizing autoimmune myopathy (NAM) and those with other idiopathic inflammatory myopathies (IIMs) or non-NAM.

METHODS

This multicenter case-control study included patients aged ≥ 18 years who were diagnosed with IIMs by muscle pathology, and who had relevant clinical and laboratory data, including muscle enzymes, from at least 3 follow-up visits during a 1-year period. Baseline clinical and laboratory data were recorded. Serum myositis-specific autoantibodies (MSAs) were obtained on the date of recruitment.

RESULTS

Of the 70 included patients, 67% had NAM, and 33% had non-NAM. The mean age of patients was 50.5 ± 15.9 years, 67% were female, and the median duration of symptoms was 2 months (IQR, 1-4). History of cancer was significantly higher in non-NAM (21.7% vs. 2.1%, p = 0.01). Gottron's papules were significantly more prevalent in non-NAM (21.7% vs. 4.3%, p = 0.04). Non-NAM had a higher prevalence of anti-Mi-2a (17.4% vs. 2.1%, p = 0.04) and Mi-2b (17.4% vs. 0.0%, p = 0.01); however, the presence of other MSAs, including anti-HMGCR and anti-SRP, was similar between groups. Improvement in motor power and treatment intensification with glucocorticoid and/or immunosuppressive agents 3 times throughout the follow-up period was similar between groups (NAM 46.8% vs. non-NAM 34.8%, p = 0.34).

CONCLUSION

NAM is indistinguishable from non-NAM by clinical manifestations, serology, or laboratory findings, except that pathognomonic skin sign of Gottron's papules and anti-Mi2 are suggestive of dermatomyositis. The integration of clinical, serological, and pathological data is essential for making a diagnosis of NAM.Key Points• NAM is indistinguishable from non-NAM by clinical manifestations, serology, or laboratory findings.• The integration of clinical, serological, and pathological data is essential for making a diagnosis of NAM.

Immune-mediated necrotising myopathy: A critical review of current concepts

Immune-mediated necrotising myopathy (IMNM) is a relatively recently described form of idiopathic inflammatory myopathy (IIM) that is characterised by progressive proximal weakness and few extra-muscular manifestations. Prominent myonecrosis, muscle fibre regeneration and a relative paucity of intramuscular lymphocytes are seen histologically. Immunological mechanisms are believed to underpin the pathogenesis, and intense immunotherapy is frequently required. Disease is often severe and neuromuscular recovery may be poor. Recently there has been an impressive international research effort to understand and characterise this emerging condition, although much remains unknown. Significant advances in the field include the discovery of specific autoantibodies, increased understanding of the risk factors, clinical characteristics and treatment options owing to a wealth of observational studies, and the development of novel classification criteria. Herein we review the current evidence regarding the pathophysiology, clinical presentation, histological features and serological profiles associated with this condition. Diagnostic approaches are discussed, including the role of muscle MRI and antibodies targeting 3‑hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and signal-recognition peptide (SRP), and a review of current treatment recommendations is provided.

Amyotrophic Lateral Sclerosis Associated with Statin Use: A Disproportionality Analysis of the FDA's Adverse Event Reporting System

INTRODUCTION

Apparent elevations in reporting of amyotrophic lateral sclerosis (ALS)-like conditions associated with statin use have been previously described from data obtained via US and European databases.

OBJECTIVE

The aim of this study was to examine US FDA Adverse Event Reporting System (FAERS) data to compare reporting odds ratios (RORs) of ALS and ALS-like conditions between statins and other drugs, for each statin agent.

METHODS

We assessed for disproportional rates of reported ALS and ALS-related conditions for each statin agent separately by using the ROR formula. FAERS data were analyzed through September 2015.

RESULTS

RORs for ALS were elevated for all statins, with elevations possibly stronger for lipophilic statins. RORs ranged from 9.09 (6.57-12.6) and 16.2 (9.56-27.5) for rosuvastatin and pravastatin (hydrophilic) to 17.0 (14.1-20.4), 23.0 (18.3-29.1), and 107 (68.5-167) for atorvastatin, simvastatin, and lovastatin (lipophilic), respectively. For simvastatin, an ROR of 57.1 (39.5-82.7) was separately present for motor neuron disease.

CONCLUSION

These findings extend previous evidence showing that significantly elevated ALS reporting extends to individual statin agents, and add to concerns about potential elevated occurrence of ALS-like conditions in association with statin usage.

A rare cause of proximal muscle weakness: immune necrotising myopathy

Background Immune-mediated necrotising myopathies are characterised clinically by the subacute onset of proximal limb weakness, accompanied by elevated creatinine kinase levels. They are distinguished from other myopathies by the absence of prominent infiltration of the muscle with inflammatory cells in the biopsies. Case presentation A 44-year-old man presented with upper extremity weakness and dysphagia. Laboratory tests included a creatinine kinase level of 4362 U/L (normal: 52-336 U/L). Rheumatological markers were all negative. A muscle biopsy showed multiple necrotic fibres with minimal inflammatory infiltration. One gram of methylprednisolone (IV) was given, followed by 1 mg/kg of methylprednisolone daily by the oral route. Intravenous immunoglobulin (0.4 mg/kg/day) was given for five days. Muscle weakness regressed and dysphagia disappeared with treatment. The patient remains well in the 23rd month of treatment, taking 5 mg/day prednisolone and monthly intravenous immunoglobulin. Conclusion Treatment of immune-mediated necrotising myopathy can be challenging as evidence-based therapeutic options are limited. It is generally accepted that early and extensive immunosuppression, including glucocorticoids as first-line agents, may be required.

18F-FDG PET/CT and MRI in Necrotizing Autoimmune Myopathy: "The Scarface Sign"

Necrotizing autoimmune myopathy (NAM) is a relatively newly recognized subgroup of idiopathic inflammatory myopathies. The common histopathologic features are myocyte necrosis without significant inflammation. Necrotizing autoimmune myopathy can be associated with connective tissue disorders but can also be triggered by viral infections such as human immunodeficiency virus or malignancy, be statin-induced NAM, or be idiopathic. Here, the authors present the case of a 58-year-old man who was referred to our PET unit for a suspected paraneoplastic syndrome in a context of NAM. Complementary contrast-enhanced CT and 3-dimensional T1-weighted MRI were carried out subsequently in order to resolve the PET/CT abnormalities.

Clinico-serologic features of statin-induced necrotising autoimmune myopathy in a single-centre cohort

Statin-induced necrotising autoimmune myopathy (NAM) is a rare but disabling complication of statin therapy. Data regarding treatment and outcomes in these patients is sparse. We retrospectively identified those patients with a diagnosis of statin-induced NAM who were managed in a single-tertiary referral centre from January 2014 to January 2017. Data regarding clinical features, serology, antibody status and functional outcome was collected. We identified 16 patients diagnosed with statin-induced NAM. Truncal weakness was present in 9/16 patients, of which one patient presented with camptocormia. Following treatment, the mean improvement in the 8-point manual muscle test (MMT8) score was 11 points (range 1-25). Antibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) were detected in 8/14 patients tested. Of patients who were HMGCR positive, 7/8 had significant truncal weakness, compared with 1/6 who were anti-HMGCR negative. In 4/7 patients who had anti-HMGCR retested following treatment, these antibodies subsequently became undetectable. The disappearance of anti-HMGCR was accompanied by sustained clinical improvement in all four patients. The mean Karnofsky Performance Status (KPS) prior to diagnosis was 89/100, and at latest follow-up had fallen to 68/100. We report a novel association of anti-HMGCR antibodies with truncal weakness in patients with statin-induced NAM. Functional impairments persist despite normalisation of muscle strength. Anti-HMGCR antibodies may disappear with treatment, paralleled by clinical remission of disease. Further prospective clinical trials are needed to determine optimal management strategies for statin-induced NAM.

Necrotizing Autoimmune Myopathy: A Unique Subset of Idiopathic Inflammatory Myopathy

Necrotizing autoimmune myopathy (NAM) is a recently recognized entity within the spectrum of idiopathic inflammatory myopathies. Diagnosis critically rests on histopathologic demonstration of macrophage predominant myocyte destruction, with few to no lymphocytes. We report our experience with identifying and treating this subset of inflammatory myositis, highlighting the importance of muscle biopsy in diagnosis, association with statin use and malignancy, and challenges of therapy.We present 3 cases that presented to 2 hospitals within our academic system in calendar year 2014 with acute/subacute onset of profound proximal muscle weakness and markedly elevated creatine kinase levels. All patients had been exposed to statins for varying periods. While each electromyogram (EMG) study showed changes with a diffuse inflammatory myopathy, it was not until muscle biopsy was performed when histopathologic features consistent with NAM solidified the diagnosis in all 3 cases. While high-dose glucocorticoids helped provide some degree of improvement in symptoms, none of our cases returned to their preillness baseline independent functioning. Additional immunosuppressive therapy was considered in each case but limited because of comorbidities.These cases demonstrate the importance of pursuing muscle biopsy in all patients with proximal muscle weakness and markedly elevated creatine kinase levels. While symptoms appear consistent with polymyositis, only through muscle biopsy can the diagnosis of NAM be made. Statins have been implicated in NAM, acting through an antibody-dependent mechanism. Combination immunosuppressive therapy has been advocated, but our patient's comorbidities precluded safe use of medications beyond glucocorticoids.

Diagnosis and Management of Immune-Mediated Myopathies

Immune-mediated myopathies (IMMs) are a heterogeneous group of acquired muscle disorders characterized by muscle weakness, elevated creatine kinase levels, and myopathic electromyographic findings. Most IMMs feature the presence of inflammatory infiltrates in muscle. However, the inflammatory exudate may be absent. Indeed, necrotizing autoimmune myopathy (NAM), also called immune-mediated necrotizing myopathy, is characterized by a necrotizing pathologic process with no or minimal inflammation in muscle. The recent discovery of antibodies associated with specific subtypes of autoimmune myopathies has played a major role in characterizing these diseases. Although diagnostic criteria and classification of IMMs currently are under revision, on the basis of the clinical and muscle histopathologic findings, IMMs can be differentiated as NAM, inclusion body myositis (IBM), dermatomyositis, polymyositis, and nonspecific myositis. Because of recent developments in the field of NAM and IBM and the controversies around polymyositis, this review will focus on NAM, IBM, and dermatomyositis.

A Rare Case of Necrotizing Myopathy and Fibrinous and Organizing Pneumonia with Anti-EJ Antisynthetase Syndrome and SSA Antibodies

Patient: Male, 34

Final Diagnosis: Necrotizing myopathy • fibrinous • organizing pneumonia

Symptoms: Short of breath • weakness in limbs

Medication: —

Clinical Procedure: —

Specialty: Rheumatology

A 64-Year-Old Woman with Chest Pain, Limb Weakness, and Endometrial Cancer

Necrotizing autoimmune myopathy (NAM) is a rare subgroup of idiopathic inflammatory myopathies (IIM). This pathology usually affects proximal limb muscles and in some cases the myocardium. Patients usually display proximal limb weakness. Muscular biopsy is required to confirm the diagnosis. We report the case of a 64-year-old woman with an atypical first presentation of NAM, manifested by chest pain in the context of metastatic endometrial cancer. The diagnosis of NAM was however made when she returned a second time with proximal limb weakness. A treatment with prednisone was then initiated, to which rituximab was rapidly associated, beside a specific chemotherapy.

A case of anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase antibody-positive paraneoplastic necrotizing myopathy associated with advanced gastric cancer that responded to intravenous immunoglobulin therapy

A 49-year-old woman presented with progressive muscle weakness of the limbs and dysphagia. Her past and family medical history were unremarkable and she did not take statins or any other medications. Laboratory tests showed that serum levels of creatine kinase were elevated (13,565 IU/l) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies were detected in the serum. Other autoantibodies to the nuclear (ANA), RNP, aminoacyl-tRNA synthetases (ARS), and signal recognition particle (SRP) were negative. Pathological analysis of the left biceps muscle revealed minimal lymphocytic infiltration into the muscle fibers together with many necrotic and regenerated fibers, which corresponded to necrotizing myopathy. Abdominal CT and upper gastrointestinal endoscopy showed an advanced gastric cancer with lymph node metastasis. The patient was subsequently diagnosed with anti-HMGCR antibody-positive paraneoplastic necrotizing myopathy associated with advanced gastric cancer. The patient underwent radical surgery to remove the cancer and was initially treated with oral prednisolone and intravenous methylprednisolone pulse therapy; however, her symptoms worsened and she became bedridden. After an additional treatment with intravenous immunoglobulin (IVIg), she showed noticeable improvements in muscle strength and dysphagia and became ambulatory. This case and recent case-series studies suggest that anti-HMGCR antibody-positive necrotizing myopathy may be included in paraneoplastic syndrome and that physicians should screen for malignant tumors in patients with anti-HMGCR antibody-positive necrotizing myopathy. Moreover, IVIg can be a useful therapy in patients with anti-HMGCR antibody-positive paraneoplastic necrotizing myopathy who show refractoriness to tumor resection and corticosteroid therapies.

Anti-HMGCR Autoantibodies in Juvenile Idiopathic Inflammatory Myopathies Identify a Rare but Clinically Important Subset of Patients

Objective.

We aimed to establish the prevalence and clinical associations of anti-HMG-CoA-reductase (anti-HMGCR) in a large UK cohort with juvenile myositis.

Methods.

There were 381 patients investigated for anti-HMGCR using ELISA.

Results.

Anti-HMGCR autoantibodies were detected in 4 patients (1%). These children had no or minimal rash and significant muscle disease. Muscle biopsies were considered distinctive, with widespread variation in fiber size, necrotic fibers, and chronic inflammatory cell infiltrates; all had prolonged elevation of creatine kinase and all ultimately received biologic therapies.

Conclusion.

Anti-HMGCR in UK children with myositis are associated with severe disease that is poorly responsive to standard treatment.

Immune-mediated necrotizing myopathy

BACKGROUND

Immune-mediated necrotizing myopathy (IMNM) is a newly identified subgroup of idiopathic inflammatory myopathies. It is defined as a rare and severe disease, with symmetrical and proximal muscle weakness and a characteristic histology. An autoimmune aspect of IMNM is suggested by its association with autoantibodies directed against signal recognition particle (SRP) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the majority of patients. Statin use is strongly associated with anti-HMGCR-positive IMNM. The pathophysiological mechanisms of this disease are still poorly understood, and as a result, no therapeutic strategy has been validated to date.

OBJECTIVE

The aim of this article is to provide an overview of the current knowledge about epidemiology, clinical features, and pathophysiology of IMNM, as well as treatment strategies.

RESULTS AND CONCLUSION

IMNM is a subject of widespread interest, with quick and meaningful advances being made. In recent years, huge progress has been made in terms of diagnosis and patient management. However, the understanding of pathophysiological mechanisms and treatment strategies still requires further investigation.

[Inflammatory myopathies]

Inflammatory myopathies comprise heterogeneous, often multisystemic autoimmune diseases with muscle involvement as a common feature. The prognosis largely depends on a timely diagnosis and initiation of therapy. Given the complexity of these rare diseases, when an inflammatory myopathy is suspected patients should be referred to an expert center with established algorithms for the diagnostic work-up. The differential diagnostic exclusion of myositis mimics should ideally be carried out in close collaboration with neurologists and neuropathologists. The choice of immunosuppressive treatment should primarily depend on disease severity and organ involvement but age and comorbidities also have to be taken into account.

Paraneoplastic Necrotizing Autoimmune Myopathy in a Patient Undergoing Laparoscopic Pancreatoduodenectomy for Distal Cholangiocarcinoma

A 73-year-old male presented with jaundice and severe muscle weakness. He was diagnosed with distal cholangiocarcinoma and paraneoplastic necrotizing autoimmune myopathy (NAM). Treatment of NAM consisted of dexamethasone pulse therapy, prednisone, and single-dose intravenous immunoglobulin. The distal cholangiocarcinoma was resected through a total laparoscopic pancreatoduodenectomy. After hospital discharge, muscle strength initially increased postoperatively; however, pneumonia resulted in the deterioration of his general condition and death 5 months after the diagnosis of paraneoplastic NAM.

Treatment and outcomes in necrotising autoimmune myopathy: An Australian perspective

Necrotising Autoimmune Myopathy (NAM) presents as a subacute proximal myopathy with high creatine kinase levels. It is associated with statin exposure, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibody, connective tissue diseases, signal recognition particle (SRP) antibody and malignancy. This case series presents our Western Australian NAM patient cohort: comparing the subgroup presentations, biopsy appearance and treatment outcomes. We retrospectively collected data on patients diagnosed with NAM at the Western Australian Neuroscience Research Institute between the years 2000 and 2015. We identified 20 patients with Necrotising Autoimmune Myopathy: 14 with anti-HMGCR antibodies; two with anti-SRP antibodies; three with connective tissue disease; two as yet unspecified. Median creatine kinase level was 6047units/L (range 1000-17000). The statin naïve patients with HMGCR antibodies and patients with SRP antibodies were the most severely affected subgroups, with higher creatine kinase levels, and were more resistant to immunotherapy. Two or more immunotherapy agents were required in 90%; eight patients required IVIG and rituximab. Steroid weaning commonly precipitated relapses. Four patients had complete remission, and the remaining patients still require immunotherapy. Necrotising Autoimmune Myopathy is a potentially treatable myopathy, which can be precipitated by statin therapy and requires early, aggressive immunotherapy, usually requiring multiple steroid sparing agents for successful steroid weaning.

Autoimmune Myopathies: Where Do We Stand?

Autoimmune diseases (AIDs) as a whole represent a major health concern and remain a medical and scientific challenge. Some of them, such as multiple sclerosis or type 1 diabetes, have been actively investigated for many decades. Autoimmune myopathies (AIMs), also referred to as idiopathic inflammatory myopathies or myositis, represent a group of very severe AID for which we have a more limited pathophysiological knowledge. AIM encompass a group of, individually rare but collectively not so uncommon, diseases characterized by symmetrical proximal muscle weakness, increased serum muscle enzymes such as creatine kinase, myopathic changes on electromyography, and several typical histological patterns on muscle biopsy, including the presence of inflammatory cell infiltrates in muscle tissue. Importantly, some AIMs are strongly related to cancer. Here, we review the current knowledge on the most prevalent forms of AIM and, notably, the diagnostic contribution of autoantibodies.

Idiopathic Inflammatory Myopathies: Clinical Approach and Management

Idiopathic inflammatory myopathies (IIM) are a group of chronic, autoimmune conditions affecting primarily the proximal muscles. The most common types are dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myopathy (NAM), and sporadic inclusion body myositis (sIBM). Patients typically present with sub-acute to chronic onset of proximal weakness manifested by difficulty with rising from a chair, climbing stairs, lifting objects, and combing hair. They are uniquely identified by their clinical presentation consisting of muscular and extramuscular manifestations. Laboratory investigations, including increased serum creatine kinase (CK) and myositis specific antibodies (MSA) may help in differentiating clinical phenotype and to confirm the diagnosis. However, muscle biopsy remains the gold standard for diagnosis. These disorders are potentially treatable with proper diagnosis and initiation of therapy. Goals of treatment are to eliminate inflammation, restore muscle performance, reduce morbidity, and improve quality of life. This review aims to provide a basic diagnostic approach to patients with suspected IIM, summarize current therapeutic strategies, and provide an insight into future prospective therapies.

Isolated gluteal and paravertebral muscle weakness due to anti-3-hydroxy-3-methylglutaryl-coenzyme a reductase antibody-associated necrotizing autoimmune myopathy

INTRODUCTION

A 56-year-old man with a distant history of statin use presented with progressive isolated very proximal lower limb and truncal weakness. Electromyogram (EMG) showed isolated gluteal and lumbar paraspinal muscle involvement.

METHODS

Gluteus medius muscle biopsy was performed under general anesthesia.

RESULTS

The biopsy showed a pauci-inflammatory necrotizing myopathy. Serum antibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) were positive. He has since partially responded to corticosteroids and methotrexate.

CONCLUSIONS

Anti-HMGCR-associated necrotizing autoimmune myopathy (NAM) can present in a restricted form after cessation of a statin. Biopsy of a symptomatic but uncommonly studied muscle is worthwhile. Muscle Nerve 54: 150-152, 2016.

Causes of creatine kinase levels greater than 1000 IU/L in patients referred to rheumatology

Patients with severely elevated creatine kinase (CK) concentrations are commonly referred to rheumatologists to evaluate for the presence of an idiopathic inflammatory myopathy (IIM). However, no studies have evaluated the frequency with which IIMs are encountered in this clinical scenario. The Vanderbilt Synthetic Derivative, a de-identified copy of over 2 million patient records, was searched to identify adult patients with a CK greater than 1000 IU/L who had been evaluated by a rheumatologist. Each patient was assigned a diagnosis using a pre-determined algorithm. The records were then reviewed for pertinent demographic data and clinical characteristics. A total of 192 patients were included for analysis. Of these patients, 105 (55 %) were diagnosed with an IIM. The non-IIM causes were drug/toxin exposure (n = 16, 8 %), infection (n = 12, 6 %), trauma (n = 10, 5 %), myocardial injury (n = 5, 3 %), hypothyroidism (n = 4, 2 %), muscular dystrophy (n = 4, 2 %), neuropsychiatric disorder (n = 3, 2 %), metabolic myopathy (n = 2, 1 %), idiopathic CK elevation (n = 11, 6 %), and other diagnoses (n = 20, 10 %). Several characteristics were found to be significantly different between IIM and non-IIM cases. In particular, patients with an IIM were more likely to be female, have a positive ANA, have interstitial lung disease, and have proximal, symmetric weakness. This study found that approximately half of patients referred to our division of rheumatology with a CK greater than 1000 IU/L were diagnosed with an IIM. Given the importance of prompt diagnosis and treatment of these disorders, rapid assessment by the consulting rheumatologist for these patients is recommended.

Signal recognition particle immunoglobulin g detected incidentally associates with autoimmune myopathy

Introduction: Paraneoplastic autoantibody screening of 150,000 patient sera by tissue‐based immunofluorescence incidentally revealed 170 with unsuspected signal recognition particle (SRP) immunoglobulin G (IgG), which is a recognized biomarker of autoimmune myopathy. Of the 77 patients with available information, 54 had myopathy. We describe the clinical/laboratory associations. Methods: Distinctive cytoplasm‐binding IgG (mouse tissue substrate) prompted western blot, enzyme‐linked immunoassay, and immunoprecipitation analyses. Available histories were reviewed. Results: The immunostaining pattern resembled rough endoplasmic reticulum, and mimicked Purkinje‐cell cytoplasmic antibody type 1 IgG/anti‐Yo. Immunoblotting revealed ribonucleoprotein reactivity. Recombinant antigens confirmed the following: SRP54 IgG specificity alone (17); SRP72 IgG specificity alone (3); both (32); or neither (2). Coexisting neural autoantibodies were identified in 28% (low titer). Electromyography revealed myopathy with fibrillation potentials; 78% of biopsies had active necrotizing myopathy with minimal inflammation, and 17% had inflammatory myopathy. Immunotherapy responsiveness was typically slow and incomplete, and relapses were frequent on withdrawal. Histologically confirmed cancers (17%) were primarily breast and hematologic, with some others. Conclusions: Autoimmune necrotizing SRP myopathy, both idiopathic and paraneoplastic, is underdiagnosed in neurological practice. Serological screening aids early diagnosis. Cancer surveillance and appropriate immunosuppressant therapy may improve outcome. Muscle Nerve53: 925–932, 2016

Immunotherapies for Immune-Mediated Myopathies: A Current Perspective

Until recently, the treatment of immune-mediated inflammatory myopathies has largely been empirical with glucocorticoids, steroid-sparing immunosuppressive drugs, and intravenous immunoglobulin. However, a proportion of patients are only partially responsive to these therapies, and there has been a need to consider alternative treatment approaches. In particular, patients with inclusion body myositis are resistant to conventional immunotherapies or show only a transient response, and remain a major challenge. With increasing recognition of the different subtypes of immune-mediated inflammatory myopathies, and improved understanding of their pathogenesis, more targeted treatments are now being trialled. The overall approach to treatment, and novel therapies targeting B cells, T cells, and specific cytokines are discussed in this review.

An Unusual Case of Statin-Induced Myopathy: Anti-HMGCoA Necrotizing Autoimmune Myopathy

Statins are some of the most widely prescribed medications, and though generally well tolerated, can lead to a self-limited myopathy in a minority of patients. Recently, these medications have been associated with a necrotizing autoimmune myopathy (NAM). Statin-associated NAM is characterized by irritable myopathy on electromyography (EMG) and muscle necrosis with minimal inflammation on muscle biopsy. The case presented is a 63-year-old woman who has continued elevation of creatine kinase (CK) after discontinuation of statin therapy. She has irritable myopathy on EMG and NAM is confirmed by muscle biopsy. She subsequently tests positive for an experimental anti-3-hydroxy-3-methylglutaryl-coenzyme A (anti-HMGCoA) antibody that is found to be present in patients with statin-associated NAM. Though statin-associated NAM is a relatively rare entity, it is an important consideration for the general internist in patients who continue to have CK elevation and weakness after discontinuation of statin therapy. Continued research is necessary to better define statin-specific and dose-dependent risk, as well as optimal treatment for this condition.