Anti-HMGCR antibodies demonstrate high diagnostic value in the diagnosis of immune-mediated necrotizing myopathy following statin exposure

Immune-mediated necrotizing myopathy: A comprehensive review of the pathogenesis, clinical features, and treatments

Immune-mediated necrotizing myopathy (IMNM) is a rare and newly recognized autoimmune disease within the spectrum of idiopathic inflammatory myopathies. It is characterized by myositis-specific autoantibodies, elevated serum creatine kinase levels, inflammatory infiltrate, and weakness. IMNM can be classified into three subtypes based on the presence or absence of specific autoantibodies: anti-signal recognition particle myositis, anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase myositis, and seronegative IMNM. In recent years, IMNM has gained increasing attention and emerged as a research hotspot. Recent studies have suggested that the pathogenesis of IMNM is linked to aberrant activation of immune system, including immune responses mediated by antibodies, complement, and immune cells, particularly macrophages, as well as abnormal release of inflammatory factors. Non-immune mechanisms such as autophagy and endoplasmic reticulum stress also participate in this process. Additionally, genetic variations associated with IMNM have been identified, providing new insights into the genetic mechanisms of the disease. Progress has also been made in IMNM treatment research, including the use of immunosuppressants and the development of biologics. Despite the challenges in understanding the etiology and treatment of IMNM, the latest research findings offer important guidance and insights for delving deeper into the disease's pathogenic mechanisms and identifying new therapeutic strategies.

Detection of Myositis Autoantibodies by Multi-Analytic Immunoassays in a Large Multicenter Cohort of Patients with Definite Idiopathic Inflammatory Myopathies

BACKGROUND

The usefulness of myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs) for the assessment of idiopathic inflammatory myopathies (IIMs) is acknowledged, but laboratory standardization remains a challenge. We detected MSAs/MAAs by multi-analytic line immunoassay (LIA) and particle-based multi-analyte technology (PMAT) in a multicenter cohort of patients with IIMs.

METHODS

We tested the sera from 411 patients affected with definite IIM, including 142 polymyositis (PM), 147 dermatomyositis (DM), 19 cancer-associated myositis, and 103 overlap myositis syndrome (OM), and from 269 controls. MSAs/MAAs were determined by 16Ags LIA in all sera, and anti-HMGCR by ELISA in 157/411 IIM sera and 91/269 control sera. The analytical specificity of LIA/HMGCR ELISA was compared with that of PMAT in 89 MSA+ IIM sera.

RESULTS

MSAs/MAAs were positive in 307/411 (75%) IIM patients and 65/269 (24%) controls by LIA (Odds Ratio 9.26, 95% CI 6.43-13.13, p < 0.0001). The sensitivity/specificity of individual MSAs/MAAs were: 20%/100% (Jo-1), 3%/99.3% (PL-7), 4%/98.8% (PL-12), 1%/100% (EJ), 0.7%/100% (OJ), 9%/98% (SRP), 5.6%/99.6% (TIF1γ), 4.6%/99.6% (MDA5), 8%/96% (Mi-2), 1.5%/98% (NXP2), 1.7%/100% (SAE1), 4%/92% (Ku), 8.5%/99% (PM/Scl-100), 8%/96% (PM/Scl-75), and 25.5%/79% (Ro52). Anti-HMGCR was found in 8/157 (5%) IIM patients and 0/176 (0%) controls by ELISA (p = 0.007). Concordance between LIA/HMGCR ELISA and PMAT was found in 78/89 (88%) samples. Individual MSAs detected by LIA were associated with IIM subsets: Jo-1 with PM and OM, PL-12 with OM, Mi-2, TIF1γ, and MDA5 with DM, SRP with PM, and PM/Scl-75/100 with OM (p < 0.001 for all).

CONCLUSIONS

Since MSAs are mostly mutually exclusive, multi-specific antibody profiling seems effective for a targeted clinical-serologic approach to the diagnosis of IIMs.

A tough pill to swallow: Two cases of statin-induced necrotizing autoimmune myopathy manifesting as dysphagia and transaminitis

Although 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors are well tolerated, a small subset of patients may develop autoimmune myopathy, classified as immune-mediated necrotizing myopathy. Statin-induced immune-mediated necrotizing myopathy can present as proximal muscle weakness and in some cases as dysphagia and respiratory distress. We present two cases of patients taking statins who developed dysphagia and muscle weakness found to have statin-induced immune-mediated necrotizing myopathy. Both patients were treated with immunosuppressive therapy: one did well clinically, while the other had an aggressive form of statin-induced immune-mediated necrotizing myopathy and succumbed to the disease. Although statin-induced immune-mediated necrotizing myopathy is rare, early treatment to induce remission of this disabling condition should be initiated to prevent morbidity and mortality.

Epidemiological and genetic features of anti-3‑hydroxy-3-methylglutaryl-CoA reductase necrotizing myopathy: Single-center experience and literature review

OBJECTIVE

To characterize the demographic, genetic, clinical, and serological features of patients with anti-3‑hydroxy-3-methylglutaryl-CoA reductase (HMGCR) immune-mediated necrotizing myopathy (IMNM) in a region of northern Spain.

METHODS

Study of all patients diagnosed with anti-HMGCR IMNM during a 5-year period at a reference hospital in northern Spain. Besides clinical and laboratory data, we analyzed the genetic influence of HLA genes and the rs4149056 (c.521T>C) single nucleotide polymorphism (SNP) in the SLCO1B1 gene.

RESULTS

8 patients (5 women, 3 men) with a mean ± SD age of 64.9 ± 7.3 years, fulfilled the criteria for anti-HMGCR IMNM. The incidence rate was 0.6 per 100.000 person-years and the prevalence 3 per 100.000 population. All patients had been exposed to statins. All of them had predominant lower limb proximal and symmetric muscle weakness that was severe in 2 and had elevated serum CK levels with a median [IQR] of 4488 [2538-9194] IU/L. Serum 25‑hydroxy vitamin D levels were decreased in all patients in whom it was determined. The 3 patients with a previous diagnosis of hypothyroidism had abnormal levels of TSH at the time of diagnosis. All patients experienced improvement with different schemes of immunosuppressive therapy. Noteworthy, 7 of 8 patients carried the HLA-DRB1*11 allele. The frequency of the rs4149056 C allele in the SLCO1B1 gene (12.5%) was similar to that of the general population.

CONCLUSION

In northern Spain, anti-HMGCR IMNM preferentially affects people over 50 years of age who are carriers of the HLA-DRB1*11 allele and take statins. Both low vitamin D levels and hypothyroidism may play a potential predisposing role in the development of this disease.

Statin-Associated Autoimmune Myopathy: Review of the Literature

OBJECTIVE

Statin-associated autoimmune myopathy (SAAM) is a rare adverse event characterized by progressive muscle symptoms despite discontinuation, requiring immunosuppressive therapy for remission. The objective of this review was to characterize SAAM, for timely detection, while examining the literature for effective treatment considerations.

METHODS

PubMed search was conducted from 2010 to 2020 was for relevant case series and studies of at least 8 patients displaying muscle discomfort or weakness, anti-HMGCR antibodies, exposure to statins, and biopsies consistent with SAAM.

RESULTS

Three case series and 3 case cohort studies identified 199 patients with SAAM. Exhibiting a mean age of 63.74 years, patients were more likely Caucasian (81%) and female (1.2X), and required a mean duration of 4.75 years before symptomatic. The presentation involved proximal muscle weakness (94%), myalgias (37%) and dysphagia (23%), accompanied by a mean creatinine kinase of 6383 IU/L. Most patients (57%) required 2 or more immunosuppressive (IMS) agents to achieve 62% remission. After 2 years of treatment, 15% of patients without remission reported symptomatic improvement, while another 12% were refractory to treatment.

CONCLUSION

Delayed onset of SAAM greater than 4 years from statin initiation may create a low index of suspicion. However, progression of symptoms beyond 2 months from statin discontinuation and positive anti-HMGCR antibodies requires immunosuppressive agents. Data and expert opinion support use of at least two IMS medications upon diagnosis for a minimum of 2 years. Therapy success depends on timely recognition and initiation of IMS combinations to achieve earlier remission and symptomatic improvement.

Generalised oedema as a presenting manifestation of inflammatory myopathy

Polymyositis is an immune-mediated inflammatory myopathy usually presenting with weakness of proximal muscles in a symmetric pattern. Generalised subcutaneous oedema as presenting feature of inflammatory myopathy, especially polymyositis, has rarely been reported. We report here a case of a young woman who was admitted to our facility with generalised severe subcutaneous oedema. During hospital stay, she gradually developed significant proximal muscle weakness with bulbar symptoms. The initial presentation of the patient masqueraded with other causes of anasarca. However, detailed clinical features, laboratory evaluation, electromyography and muscle biopsy clinched the diagnosis of polymyositis. She was treated with systemic corticosteroids and azathioprine. The patient responded well to treatment and the swelling gradually subsided.

Paraneoplastic myopathy in pancreatic cancer: a case report and literature review

Dermatomyositis (DM) and polymyositis (PM) are both immune-mediated inflammatory myopathies known to occur in paraneoplastic syndromes associated with a new diagnosis of malignancy, most commonly breast, ovarian, lung, pancreatic, stomach, colorectal, and Non-Hodgkin’s lymphoma¹ in DM and breast, lung, bladder cancer, and Non-Hodgkin’s lymphoma in PM. ^2,3,4 While inflammatory markers such as creatine kinase (CK) may be elevated with either DM or PM, marked elevation is rare. Herein, we report a case of newly diagnosed pancreatic cancer presenting with inflammatory myopathy and marked CK elevation. We review the frequency of PM as a paraneoplastic syndrome, the association with marked CK elevation, and the association with pancreatic cancer.

Intravenous immunoglobulins as first-line treatment in idiopathic inflammatory myopathies: a pilot study

OBJECTIVES

We explored efficacy and safety of IVIg as first-line treatment in patients with an idiopathic inflammatory myopathy.

METHODS

In this investigator-initiated phase 2 open-label study, we included 20 adults with a newly diagnosed, biopsy-proven idiopathic inflammatory myopathy, and a disease duration of less than 9 months. Patients with IBM and prior use of immunosuppressants were excluded. The standard treatment regimen consisted of IVIg (Privigen) monotherapy for 9 weeks: a loading dose (2 g/kg body weight) and two subsequent maintenance doses (1 g/kg body weight) with a 3-week interval. The primary outcome was the number of patients with at least moderate improvement on the 2016 ACR/EULAR Total Improvement Score. Secondary outcomes included time to improvement, the number of patients requiring rescue medication and serious adverse events.

RESULTS

We included patients with DM (n = 9), immune-mediated necrotizing myopathy (n = 6), non-specific myositis/overlap myositis (n = 4) and anti-synthetase syndrome (n = 1). One patient was excluded from analyses because of minimal weakness resulting in a ceiling effect. Eight patients (8/19 = 42.0%; Clopper-Pearson 95% CI: 19.6, 64.6) had at least moderate improvement by 9 weeks. Of these, six reached improvement by 3 weeks. Seven patients required rescue medication due to insufficient efficacy and prematurely ended the study. Three serious adverse events occurred, of which one was pulmonary embolism.

CONCLUSION

First-line IVIg monotherapy led to at least moderate improvement in nearly half of patients with a fast clinical response in the majority of responders.

TRIAL REGISTRATION

Netherlands Trial Register identifier, NTR6160.

Necrotising myopathy and concurrent thyroiditis in a patient with COVID-19 infection

A 76-year-old man with hypogammaglobulinemia on monthly intravenous immunoglobulin infusions presented to the hospital with fever, cough, and shortness of breath and was diagnosed with COVID-19 pneumonia requiring intensive care unit admission but not intubation. He was treated with convalescent plasma, remdesivir and corticosteroids. Sixteen days into his hospitalisation he began to report weakness without sensory symptoms and was found on biopsy to have a necrotising myopathy.

Atorvastatin-Induced Necrotizing Myopathy and its Response to Combination Therapy

Atorvastatin is the most commonly used statin medication to decrease cholesterol levels and prevent atherosclerosis. Myopathy is a reported side effect of atorvastatin which can happen even after more than six months after starting the medication. The side effect on the muscle tissue can range from simple reversible myalgia to respiratory muscle compromise. Here we present a 46-year-old male who presented with myopathy after taking atorvastatin for two years. Biopsy proved immune-mediated necrotizing myopathy which responded to a combination of Rituximab and intravenous immunoglobulin therapy.

A case of statin-associated immune-mediated necrotizing myopathy with atypical biopsy features

Statin-associated immune-mediated necrotizing myopathy (IMNM) is a rare presentation of a statin-associated myopathy. Patients usually present with muscle weakness and pain in the setting of statin use with elevated creatine kinase (CK) levels and a positive anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody. Muscle biopsies typically show necrosis, CD68+ macrophages, and minimal lymphocytes. We present a case of a 67-year-old woman who had 2 months of progressive weakness and bilateral lower extremity pain after initiating atorvastatin therapy with symptoms persisting after statin cessation. She was found to have high anti-HMGCR antibody titers, and the biopsy of the rectus femoris muscle showed a prominent endomysial inflammatory cell infiltrate with necrotic and regenerative fibers and an atypical extensive inflammatory infiltrate composed of both CD4+ helper T cells and CD8+ cytotoxic T cells. She showed symptom resolution and normalization of CK levels and inflammatory markers with treatment involving a prolonged prednisone taper and a brief course of azathioprine, which was stopped because of the adverse effects.

Immune-mediated necrotizing myopathy: clinical features and pathogenesis

Immune-mediated necrotizing myopathy (IMNM) is a group of inflammatory myopathies that was distinguished from polymyositis in 2004. Most IMNMs are associated with anti-signal recognition particle (anti-SRP) or anti-3-hydroxy-3-methylglutaryl-coA reductase (anti-HMGCR) myositis-specific autoantibodies, although ~20% of patients with IMNM remain seronegative. These associations have led to three subclasses of IMNM: anti-SRP-positive IMNM, anti-HMGCR-positive IMNM and seronegative IMNM. IMNMs are frequently rapidly progressive and severe, displaying high serum creatine kinase levels, and failure to treat IMNMs effectively may lead to severe muscle impairment. In patients with seronegative IMNM, disease can be concomitant with cancer. Research into IMNM pathogenesis has shown that anti-SRP and anti-HMGCR autoantibodies cause weakness and myofibre necrosis in mice, suggesting that, as well as being diagnostic biomarkers of IMNM, they may play a key role in disease pathogenesis. Therapeutically, treatments such as rituximab or intravenous immunoglobulins can now be discussed for IMNM, and targeted therapies, such as anticomplement therapeutics, may be a future option for patients with refractory disease.

Statin Associated Autoimmune Myonecrosis: Case Report With Delayed Onset and Treatment Challenges

PURPOSE

A case of delayed statin associated autoimmune myopathy (SAAM) is presented along with review of clinical findings and treatment strategies.

SUMMARY

A 54 year old male presented with proximal extremity weakness, difficulty ambulating, and dysphagia. Symptoms began when restarting atorvastatin 40 mg daily for a recent NSTEMI, following 10 years of statin use, interrupted after diagnosis of NASH. Relevant labs included CK of 13,618 IU/L, ALT/ AST of 568/407 IU/L, while additional liver, renal, and toxicology tests were normal. Following treatment response to prednisone 40 mg daily for 3 days, outpatient testing for anti-HMGCR antibodies was ordered.Twelve days from discharge, the patient was readmitted for myalgia and dysphagia, CK = 6042 IU/L, ALT/AST = 360/112 IU/L, and positive anti-HMGCR antibodies. Newly diagnosed with SAAM, symptoms improved with methylprednisolone and intravenous immunoglobulin (IVIG), continuing outpatient as daily prednisone and monthly IVIG. Four days later, the patient relapsed with worsened weakness and dysphagia, CK = 5812 IU/L, and ALT/AST = 647/337 IU/L. After response to methylprednisolone and rituximab, the patient was discharged on a corticosteroid taper, biweekly rituximab, and monthly IVIG. Two weeks later, a final admission involved a syncopal episode and fall, with a CK = 1461 IU/L. Treatment included IVIG, rituximab, and corticosteroid taper, which lead to remission for greater than 6 months.

CONCLUSION

Statin associated autoimmune myopathy occurred when restarting atorvastatin, following 10 years of statin use. Clinical findings and positive anti-HMGCR antibodies confirmed the diagnosis. Recurrent relapses required triple combination therapy including addition of rituximab to achieve remission.

Statin-Associated Autoimmune Myopathy: Current Perspectives

Although generally well tolerated, statin users frequently report muscle-related side effects, ranging from self-limiting myalgias to rhabdomyolysis or the rare clinical entity of statin-associated immune-mediated necrotizing myopathy (IMNM). Statin-associated IMNM is based on the development of autoantibodies against 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in cholesterol synthesis and the pharmacologic target of statins, and leads to a necrotizing myopathy requiring immunosuppressive therapy. This review attempts to recapitulate the diverse aspects of anti-HMGCR IMNM, including clinical presentation, diagnostic modalities, genetic risk associations, therapeutic options and potential pathogenetic pathways.

Immune mediated necrotizing myopathy: A rare complication of statin therapy

Immune mediated necrotizing myopathy (IMNM) is part of the inflammatory myopathies group of diseases and presents with muscle weakness, myalgias and elevated serum creatine phosphokinase (CPK). Statin-induced IMNM is a rare complication. We present a patient with IMNM secondary to simvastatin use. The patient presented with proximal myopathy, dysphagia, and elevated creatinine kinase levels, and was subsequently found to have anti-3- hydroxy-3-methylglutaryl-CoA reductase (HMGCR) autoantibodies with a necrotizing process on muscle biopsy. This patient’s case was further complicated by sequelae of multiple disease processes, ultimately leading to deterioration of his health.

Disease Specific Autoantibodies in Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies represent still a diagnostic and therapeutic challenge in different disciplines including neurology, rheumatology, and dermatology. In recent years, the spectrum of idiopathic inflammatory myopathies has been significantly extended and the different manifestations were described in more detail leading to new classification criteria. A major breakthrough has also occurred with respect to new biomarkers especially with the characterization of new autoantibody-antigen systems, which can be separated in myositis specific antibodies and myositis associated antibodies. These markers are detectable in approximately 80% of patients and facilitate not only the diagnostic procedures, but provide also important information on stratification of patients with respect to organ involvement, risk of cancer and overall prognosis of disease. Therefore, it is not only of importance to know the significance of these markers and to be familiar with the optimal diagnostic tests, but also with potential limitations in detection. This article focuses mainly on antibodies which are specific for myositis providing an overview on the targeted antigens, the available detection procedures and clinical association. As major tasks for the near future, the need of an international standardization is discussed for detection methods of autoantibodies in idiopathic inflammatory myopathies. Furthermore, additional investigations are required to improve stratification of patients with idiopathic inflammatory myopathies according to their antibody profile with respect to response to different treatment options.

Myositis-specific autoantibodies, a cornerstone in immune-mediated necrotizing myopathy

Over the past few years, myositis-specific autoantibodies played an increasing role in the inflammatory idiopathic myositis definition. They became the critical immunological marker for immune-mediated necrotizing myopathy diagnosis (IMNM) since the paradigm switch from histological to serological criteria. This review is focused on the key role of the anti-signal recognition particle (anti-SRP) and the anti-3-Hydroxy-3-MethylGlutaryl-Coenzyme A Reductase (anti-HMGCR) antibodies in immune-mediated necrotizing myopathy. Anti-SRP and anti-HMGCR antibodies are robust diagnostic tools in case of both the classical subacute form and the slowly progressive form of IMNM that may mimic muscular dystrophy. Anti-SRP and anti-HMGCR patients share clinical, biological and histological features with some antibody-associated specificity. Anti-SRP patients harbour more severe muscle weakness and atrophy with severe muscle damage on magnetic resonance imaging study. Approximately 10-20% of anti-SRP patients develop extramuscular symptoms, especially lung interstitial disease. Conversely, anti-HMGCR patients are often associated with statin exposure. In both cases, patients have a poor outcome with frequent relapse and the use of combined immunotherapy. Of note, various data suggest a direct pathogenic role of these antibodies reinforcing the interest in targeted therapeutic strategy.

Seronegative patients form a distinctive subgroup of immune-mediated necrotizing myopathy

Objectives

To investigate the characteristics of different clinico-serologic subgroups of immune-mediated necrotizing myopathy (IMNM).

Methods

We retrospectively reviewed data from medical charts of 64 patients diagnosed with IMNM between 2012 and 2017 in 3 neuromuscular referral centers in The Netherlands and 1 in Belgium.

Results

Seventeen patients had anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) autoantibodies (Abs), of whom 11 had a history of statin use, 15 had anti-signal recognition particle (SRP) Abs, 2 had anti-melanoma differentiation-associated protein 5 (MDA5) Abs, 22 patients were seronegative, and 9 patients did not have a complete Ab assessment. Moderate to severe disability in HMGCR Ab-positive and anti-SRP Ab-positive IMNM was common (71% and 60%, respectively) despite multimodality treatment. Compared with statin-associated anti-HMGCR Ab-positive IMNM, statin-naive anti-HMGCR Ab-positive IMNM patients were more often men (67% vs 45%), had lower rates of dysphagia (17% vs 45%), and more frequently had third-line therapy (50% vs 9%) and poor to fatal outcome (50% vs 0%). Compared with seropositive IMNM, seronegative IMNM was characterized by female predominance (1:3), frequent occurrence of associated connective tissue disorders (22% vs 9%), and significantly higher rates of extramuscular disease activity (50% vs 16%, p 0.014; 2-sided Fisher exact), also after excluding patients with an associated connective tissue disease (35% vs 7%, p 0.038; 2-sided Fisher exact).

Conclusions

Our findings indicate that seronegative IMNM forms a subgroup with distinctive features from seropositive IMNM.

Immunopathological Characterization of Muscle Biopsy Samples from Immune-Mediated Necrotizing Myopathy Patients

Background

Immune-mediated necrotizing myopathy (IMNM) is a relatively new proposed category of idiopathic inflammatory myopathies (IIMs), characterized by the presence of abundant necrotic muscle fibers, myophagocytosis, and sparse inflammatory infiltrates. The aim of our study was to analyze the immunopathological characteristics of IMNM by detecting biopsy samples from a cohort of patients, and to delineate the pathways involved in the pathogenesis.

Material/Methods

A retrospective evaluation of muscle biopsy samples, clinical and laboratory data, and immunohistochemical analysis of macrophages MHC-I and MAC, was performed for all patients diagnosed as having IMNM but without a prior exposure to statins.

Results

Immunohistochemical analysis revealed the presence of CD68⁺ macrophages mainly in the necrotic muscle fibers and the endomysial connective tissue. MHC-I and MAC positively stained not only the necrotic fibers or vessels but also the non-necrotic ones.

Conclusions

Our data describe general immunological features in IMNM patients, which may be helpful in serving as biomarkers, aid in diagnostic decisions, and provide clues into the underlying mechanisms involved in this disease.

Autoimmune necrotising myopathy and HMGCR antibodies

Statins lower serum cholesterol concentrations by inhibiting the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR). Muscle side effects are relatively common and include asymptomatic elevation of serum creatine kinase (CK), myalgia, proximal muscle weakness and rhabdomyolysis. More recently, a subset of cases of immune-mediated necrotising myopathy has been found to have antibodies against HMGCR. It is often an aggressive and debilitating myopathy and has a complex pathogenesis characterised by fibre necrosis, usually with minimal associated inflammation. Not all such patients are taking statins. The general consensus is that best treatment involves withdrawing the statin and giving immunosuppressive and immunomodulatory treatment. We describe three cases of HMGCR-related immune-mediated necrotising myopathy, detailing their clinical course and subsequent management, illustrating the spectrum of this disorder.