Toll-like receptors and IL-7 as potential biomarkers for immune-mediated necrotizing myopathies

We aimed to verify whether the immune system may represent a source of potential biomarkers for the stratification of immune-mediated necrotizing myopathies (IMNMs) subtypes. A group of 22 patients diagnosed with IMNM [7 with autoantibodies against signal recognition particle (SRP) and 15 against 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR)] and 12 controls were included. A significant preponderance of M1 macrophages was observed in both SRP+ and HMGCR+ muscle samples (p < 0.0001 in SRP+ and p = 0.0316 for HMGCR+ ), with higher values for SRP+ (p = 0.01). Despite the significant increase observed in the expression of TLR4 and all endosomal Toll-like receptors (TLRs) at protein level in IMNM muscle tissue, only TLR7 has been shown considerably upregulated compared to controls at transcript level (p = 0.0026), whereas TLR9 was even decreased (p = 0.0223). Within IMNM subgroups, TLR4 (p = 0.0116) mRNA was significantly increased in SRP+ compared to HMGCR+ patients. Within IMNM group, only IL-7 was differentially expressed between SRP+ and HMGCR+ patients, with higher values in SRP+ patients (p = 0.0468). Overall, innate immunity represents a key player in pathological mechanisms of IMNM. TLR4 and the inflammatory cytokine IL-7 represent potential immune biomarkers able to differentiate between SRP+ and HMGCR+ patients.

Epidemiology of the idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic autoimmune diseases that affect the skeletal muscles and can also involve the skin, joints, lungs and heart. The epidemiology of IIM is obscured by changing classification criteria and the inherent shortcomings of case identification using healthcare record diagnostic coding. The incidence of IIM is estimated to range from 0.2 to 2 per 100,000 person-years, with prevalence from 2 to 25 per 100,000 people. Although the effects of age and gender on incidence are known, there is only sparse understanding of ethnic differences, particularly in indigenous populations. The incidence of IIM has reportedly increased in the twenty-first century, but whether this is a genuine increase is not yet known. Understanding of the genetic risk factors for different IIM subtypes has advanced considerably. Infections, medications, malignancy and geography are also commonly identified risk factors. Potentially, the COVID-19 pandemic has altered IIM incidence, although evidence of this occurrence is limited to case reports and small case series. Consideration of the current understanding of the epidemiology of IIM can highlight important areas of interest for future research into these rare diseases.

Observational longitudinal study to assess the outcome of patients with idiopathic inflammatory myositis using validated tools

INTRODUCTION

There have been major changes in the classification and treatment of patients with idiopathic inflammatory myositis (IIM) in the last 2 decades. A major challenge is to identify the parameters that can affect the outcome and prognosis of these patients. Here, we have longitudinally followed a well-characterized cohort of IIM patients in a rheumatology center and reported the outcome using the validated tools.

METHOD

Patients with a clinical diagnosis of IIM and a follow-up duration of greater than 2 years were prospectively included in the study. The duration of the study was 6 years: July 2016-July 2022. Clinical details and follow-up were recorded using pro-formas and outcomes were noted using validated tools. Ethics approval and written informed consent were taken.

RESULTS

Forty patients had a clinical diagnosis of IIM. Mean follow-up duration was 43.8 (15) months. Out of 40 patients, 32 (80%) achieved remission (8 patients each were off corticosteroid and off treatment for >6 months), 5 (12%) expired and 3 (8%) had active disease. Disease course was non-relapsing in 22/35 (73%) patients. Mean manual muscle testing-8 score (n = 29) and myositis disease activity assessment tool score (n = 35) at the final visit were 75.6 (6.8) and 0.048 (0.07) respectively. Thirteen patients had damage (37%). Patients with disease duration >1 year at the time of presentation were more likely to develop chronic-continuous disease course (P = .023, odds ratio [OR] = 7.6), more frequently required second-line or third-line immunosuppression (P = .001, OR = 24) with higher myositis damage index score (p = .0002, OR = 47).

CONCLUSIONS

IIM patients had good outcomes with the majority achieving remission and near-complete muscle recovery. However, the patients presenting late to the rheumatologists were more likely to have smoldering disease, more immunosuppressive medicines, and greater accumulated damage.

Exploring challenges in the management and treatment of inclusion body myositis

PURPOSE OF REVIEW

This review provides an overview of the management and treatment landscape of inclusion body myositis (IBM), while highlighting the current challenges and future directions.

RECENT FINDINGS

IBM is a slowly progressive myopathy that predominantly affects patients over the age of 40, leading to increased morbidity and mortality. Unfortunately, a definitive cure for IBM remains elusive. Various clinical trials targeting inflammatory and some of the noninflammatory pathways have failed. The search for effective disease-modifying treatments faces numerous hurdles including variability in presentation, diagnostic challenges, poor understanding of pathogenesis, scarcity of disease models, a lack of validated outcome measures, and challenges related to clinical trial design. Close monitoring of swallowing and respiratory function, adapting an exercise routine, and addressing mobility issues are the mainstay of management at this time.

SUMMARY

Addressing the obstacles encountered by patients with IBM and the medical community presents a multitude of challenges. Effectively surmounting these hurdles requires embracing cutting-edge research strategies aimed at enhancing the management and treatment of IBM, while elevating the quality of life for those affected.

Metabolic profiling of patients with different idiopathic inflammatory myopathy subtypes reveals potential biomarkers in plasma

Idiopathic inflammatory myopathy (IIM) are heterogeneous autoimmune diseases that primarily affect the proximal muscles. IIM subtypes include dermatomyositis (DM), polymyositis (PM), and anti-synthetase syndrome (ASS). Metabolic disturbances may cause irreversible structural damage to muscle fibers in patients with IIM. However, the metabolite profile of patients with different IIM subtypes remains elusive. To investigate metabolic alterations and identify patients with different IIM subtypes, we comprehensively profiled plasma metabolomics of 46 DM, 13 PM, 12 ASS patients, and 30 healthy controls (HCs) using UHPLC-Q Exactive HF mass spectrometer. Multiple statistical analyses and random forest were used to discover differential metabolites and potential biomarkers. We found that tryptophan metabolism, phenylalanine and tyrosine metabolism, fatty acid biosynthesis, beta-oxidation of very long chain fatty acids, alpha-linolenic acid and linoleic acid metabolism, steroidogenesis, bile acid biosynthesis, purine metabolism, and caffeine metabolism are all enriched in the DM, PM, and ASS groups. We also found that different subtypes of IIM have their unique metabolic pathways. We constructed three models (five metabolites) to identify DM, PM, ASS from HC in the discovery and validation sets. Five to seven metabolites can distinguish DM from PM, DM from ASS, and PM from ASS. A panel of seven metabolites can identify anti-melanoma differentiation-associated gene 5 positive (MDA5 +) DM with high accuracy in the discovery and validation sets. Our results provide potential biomarkers for diagnosing different subtypes of IIM and a better understanding of the underlying mechanisms of IIM.

Update on autoantibodies and related biomarkers in autoimmune inflammatory myopathies

Purpose of review

This manuscript reviews recently published advances in the identification of autoimmune inflammatory myopathies (AIM)-specific and AIM-related autoantibodies considered of value in the workup of patients suspected of having AIM. Newer autoantibodies, developments, and advances in the methodology of testing, the gaps and pitfalls in using these assays as diagnostic biomarkers, and the importance of considering overlap diseases and unique clinical AIM phenotypes are discussed.

Recent findings

Summary

The spectrum of autoantibodies and related biomarkers in AIM continues to expand. Many of these have clear clinical implications in regard to subsets and overlap conditions of AIM, associated malignancy and pathological findings.

Clinical characteristics and prognostic analysis of idiopathic inflammatory myopathy with positive anti-aminoacyl-tRNA synthetase antibodies: A single center experience

OBJECTIVES

To identify the differences of clinical characteristics, laboratory findings, and the long-term outcomes in patients with anti-synthetase syndrome (ASS) of different anti-aminoacyl-transfer RNA synthetase antibodies.

METHODS

We retrospectively enrolled 119 patients with ASS, and the clinical characteristics and laboratory findings were collected. Additionally, multivariate COX regression analysis was performed to estimate the risk factors of prognosis in patients with ASS.

RESULTS

The frequency of interstitial lung disease (ILD) reached 93.3% in our cohort, of 28 (23.5%) was classified as rapidly progressive (RP)-ILD. The highest incidence of RP-ILD was 36.4% in the PL12 group of ASS patients. The ILD group was characterized by an older age, a lower prevalence of V sign, and a higher prevalence of pulmonary symptoms when contrasted with the non-ILD group. There were statistical differences of clinical significance in arthritis, myositis, mechanic's hands, triad, shawl sign, V sign, and Raynaud's phenomenon among the four subgroups (all p < .05). Additionally, the prevalence rates of arthritis, myositis, mechanic's hands, triad, and V sign in the anti-Jo1 antibody-positive group were significantly higher than anti-Jo1 antibody-negative patients with ASS (all p < .05). Multivariate Cox regression analysis showed mechanic's hands (odds ratio [OR] = 6.47, p < .001), anti-nuclear antibodies (ANA) (OR = 2.13, p = .026), ILD (OR = 10.50, p < .001), and V sign (OR = 0.30, p = .007) were independent factors affecting the prognosis of patients with ASS. The incidences of RP-ILD, arthritis, myositis, triad, mechanic's hands, and shawl sign were more frequent in the anti-Ro52 antibody-positive group than the anti-Ro52 antibody-negative patients with ASS (all p < .05).

CONCLUSIONS

Patients with ASS accompanied with ILD are highly prevalent. Mechanic's hands, ANA, and ILD may be a potential biomarker for predicting a poor prognosis in patients with ASS. Additionally, the detection of the anti-Ro52 antibody provides valuable insights for managing and predicting disease progression and long-term outcomes.

Myositis-specific autoantibodies in a non-traveler, patient from a non-endemic country, with Plasmodium vivax malaria

INTRODUCTION

Autoantibodies (AAb) are a hallmark of immune-mediated inflammatory diseases. Malaria is a parasitic disease caused by Plasmodium protozoa. Individuals with malaria may present with a wide range of symptoms. It is frequently linked to the development of different AAb.

CASE DESCRIPTION

A 35-year-old male presented with repeated episodes of fever, malaise, myalgia, dark urine, and yellowish sclera. Initial diagnostic workup revealed severe Coombs-positive anemia, increased C-reactive protein, and procalcitonin, pathological liver tests, high concentration of serum IgE, IgG, IgM, IgA, positive antinuclear antibodies (ANA), and positive antineutrophil cytoplasmatic antibodies (ANCA). In addition, myositis-specific antibodies directed to polymiositis-scleroderma 75 protein (PmScl75), threonyl-tRNA synthetase (PL-7), alanyl-tRNA synthetase (PL-12), Mi-2 antigen (Mi-2), Ku DNA helicase complex (Ku), signal recognition particle (SRP), and antiaminoacyl tRNA synthetase (EJ) were detected. The patient was suspected of having systemic lupus erythematosus and sent to the Clinic of Allergy and Immunology for further evaluation and treatment. A peripheral blood film examined by the hematologist during an episode of fever revealed intra-erythrocytic parasitic forms of Plasmodium vivax (P. vivax). After being diagnosed with P. vivax malaria, he was transferred to the Clinic for Infective and Tropical Diseases. The therapy consisted of artesunate/mefloquine and prednisone led to a complete clinical recovery and autoantibodies gradually disappeared.

CONCLUSIONS

Malaria would not normally be considered during the initial diagnostic workup in a non-traveler and a patient from a non-endemic country. However, a thorough parasitic evaluation in patients presenting with a broad range of autoantibodies might be of particular importance.

Sintilimab-induced inflammatory myopathy in a patient with esophageal cancer: a case report

The use of immune checkpoint inhibitors (ICIs) has shown remarkable efficacy in the treatment of various malignancies, significantly reshaping cancer treatment. However, as a result of the widespread use of ICIs, several immune-related adverse events (iRAEs) have emerged, some of which can be rare and potentially fatal. In this paper, we reported the earliest case of Sintilimab used in the treatment of esophageal cancer with severe inflammatory myopathy (involving the cardiac, respiratory, and skeletal muscles)in China. This patient was an elderly female who presented to our institution with progressive limb weakness and ptosis. Prior to the onset of symptoms, the patient had undergone a radical esophagectomy for esophageal cancer, experienced several cycles of of radiotherapy and chemotherapy, as well as two doses of Sintilimab treatment. Shortly after initiating immunotherapy, the patient developed symptoms including bilateral ptosis, limb weakness, and difficulty swallowing and breathing. The levels of creatine kinase and troponin I in the patient's blood were significantly elevated, and positive results were observed for anti-skeletal and anti-cardiac muscle antibodies, indicating that the patient might be developing ICIs-related inflammatory myopathy. Fortunately, the patient responded well to treatment including corticosteroids, plasmapheresis, intravenous immunoglobulin, and other supportive therapies. Here, we discuss the incidence, mechanisms, and management strategies of fatal iRAEs. Early detection and timely intervention may be critical in reducing the incidence and mortality rates of iRAEs and improving patient outcomes.

The use of high-sensitivity cardiac troponin I in assessing cardiac involvement and Disease prognosis in idiopathic inflammatory myopathy

OBJECTIVES

Cardiac involvement is one of the most serious complications of idiopathic inflammatory myopathy (IIM) that indicates poor prognosis. However, there is a lack of effective biomarkers for the identification of cardiac involvement and the prediction of prognosis in IIM. Here, we aimed to explore the value of different cardiac biomarkers in IIM patients.

METHODS

A total of 142 IIM patients in the Department of Rheumatology and Immunology, Ruijin Hospital from July 2019 to October 2022 were included in this study. The clinical characteristics, laboratory tests, treatments and prognosis were recorded. The disease activity was assessed according to the core set measures. The correlations of the serum cardiac biomarkers levels with disease activity were analyzed by the Spearman correlation test. Risk factors for cardiac involvement were evaluated by multivariate logistic regression analysis.

RESULTS

Higher high-sensitivity cardiac troponin I (hs-cTnI) levels were associated with cardiac involvement (n = 41) in IIM patients [adjusted OR 7.810 (95% CI: 1.962-31.097); p = 0.004], independent of other serum cardiac biomarkers. The abnormal hs-cTnI had the highest AUC for distinguishing of cardiac involvement in IIM patients (AUC = 0.848, 95% CI: 0.772,0.924; p < 0.001). Besides, we found that high serum levels of hs-cTnI were significantly correlated with disease activity. Moreover, patients with higher serum levels of hs-cTnI tended to suffer from poor prognosis.

CONCLUSIONS

Serum hs-cTnI testing may play a role in screening for cardiac involvement in IIM patients. Abnormal levels of serum hs-cTnI were associated with increased disease activity and poor prognosis.

Isolated muscular sarcoidosis presenting as hypercalcaemic renal failure

The case report describes the details of a man in his 40s admitted for evaluation of renal failure. Biochemical testing revealed parathyroid hormone (PTH) -independent hypercalcaemia. The evaluations for the usual causes such as malignancies, granulomatous diseases, multiple myeloma and vitamin D toxicity were negative. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) scan identified diffuse uptake in the muscles, and the subsequent muscle biopsy showed non-caseating granulomas suggestive of granulomatous myositis, possibly sarcoidosis, in view of raised ACE levels and the absence of other causes. The patient showed a dramatic response to glucocorticoids, with prompt relief of symptoms and normalisation of serum calcium and creatinine. The case highlights the importance of considering sarcoid myositis in the evaluation of hypercalcaemia and the need for prompt initiation of glucocorticoid therapy to achieve favourable outcomes. The successful use of FDG-PET in diagnosing PTH-independent hypercalcaemia suggests its potential as a valuable tool in the diagnostic algorithm for this condition.

A Case in Which Breast Cancer Developed at the Same Time As Dermatomyositis, and the Onset of New Cancer Was Able to Be Predicted by the Exacerbating Skin Symptoms and Parallel Increase in the Anti-TIF1-γ Antibody Levels

Dermatomyositis (DM) is an idiopathic inflammatory myopathy. The incidence of malignancy in DM patients is quite high. Anti-transcription intermediary factor 1-γ (anti-TIF1-γ) antibody is more prevalent in DM patients with malignancy than in those without malignancy. A 70-year-old woman developed hoarseness and difficulty swallowing. A physical examination revealed skin abnormalities. Breast cancer was found in her right breast. She was positive for anti-TIF1-γ antibody. Chemotherapy reduced the tumor size, decreased the anti-TIF1-γ antibody level, and improved her symptoms. About 2.5 years later, however, her skin symptoms worsened, and anti-TIF1-γ antibody levels increased again, and colorectal cancer was found. Treatment with endoscopic mucosal resection (EMR) improved her symptoms again. Our case suggests that the exacerbating skin symptoms and parallel increase in the anti-TIF1-γ antibody level led to the detection of a second cancer after treatment of the first cancer in this case of DM.

Anti-Kv1.4 Antibody-positive Nivolumab-induced Myasthenia Gravis and Myositis Presenting with Bilateral Ptosis and Demonstrating Different Pathophysiologies

Nivolumab blocks inhibitors of T-cell activation and restores antitumor immunity but promotes T-cell activity in host tissues by blocking inhibition of the T-cell function, resulting in immune-related adverse effects. We herein report an 80-year-old man presenting with nivolumab-related myasthenia gravis with anti-muscular voltage-gated potassium channel-complex (Kv1.4) antibodies. On day 29 after nivolumab administration, he simultaneously developed rapidly progressing right ptosis and left facial paralysis. Nivolumab administration was discontinued. He subsequently presented with bulbar paralysis, dyspnea, and muscle weakness and received intravenous immunoglobulin, methylprednisolone, and plasma exchange. The severity of nivolumab-related myasthenia gravis with anti-Kv1.4 antibodies presented with diverse clinical findings.

Single-cell profiling of muscle-infiltrating T cells in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are rare autoimmune systemic diseases characterized by muscle weakness and the presence of muscle-infiltrating T cells. IIM represent a clinical challenge due to heterogeneity of symptoms and variability of response to immunosuppressive treatment. Here, we performed in-depth single-cell sequencing on muscle-infiltrating T cells and peripheral blood memory T cells in six patients with recently diagnosed IIM. We identified tissue resident memory T-cell (TRM ) signatures including the expression of HOBIT, XCL1 and CXCR6 in the muscle biopsies of all patients with IIM. Clonally expanded T-cell clones were mainly found among cytotoxic and TRM implying their role in the disease pathogenesis. Finally, identical expanded T-cell clones persisting at follow-up in the muscle tissue of two patients suggest their involvement in disease chronicity. Our study reveals a muscle tissue resident memory T-cell signature in patients with IIM and a transcriptomic map to identify novel therapeutic targets in IIM.

Healthcare utilization and unmet needs of patients with antisynthetase syndrome: An international patient survey

Antisynthease syndrome (ASSD) is a rare, complex and understudied autoimmune disease. Internet-based studies can overcome barriers of traditional on-site research and are therefore very appealing for rare diseases. The aim of this study was to investigate patient-reported symptoms, diagnostic delay, symptoms, medical care, health status, working status, disease knowledge and willingness to participate in research of ASSD patients by conducting an international web-based survey. The multilingual questionnaire was created by an international group of rheumatologists and patients and distributed online. 236 participants from 22 countries completed the survey. 184/236 (78.0%) were female, mean age (SD) was 49.6 years (11.3) and most common antisynthetase antibody was Jo-1 (169/236, 71.6%). 79/236 (33.5%) reported to work full-time. Median diagnostic delay was one year. The most common symptom at disease onset was fatigue 159/236 (67.4%), followed by myalgia 130/236 (55.1%). The complete triad of myositis, arthritis and lung involvement verified by a clinician was present in 42/236 (17.8%) at disease onset and in 88/236 (37.3%) during the disease course. 36/236 (15.3%) reported to have been diagnosed with fibromyalgia and 40/236 (16.3%) with depression. The most reported immunosuppressive treatments were oral corticosteroids 179/236 (75.9%), followed by rituximab 85/236 (36.0%). 73/236 (30.9%) had received physiotherapy treatment. 71/236 (30.1%) reported to know useful online information sources related to ASSD. 223/236 (94.5%) were willing to share health data for research purposes once a year. Our results reiterate that internet-based research is invaluable for cooperating with patients to foster knowledge in rare diseases.

Systemic Sclerosis with Inflammatory Myositis: A Case Report

The overlap of systemic sclerosis and inflammatory myositis is a rare disorder which results in immune system activation and production of autoantibodies. We present a case of a 28-year-old female with complaints of generalized weakness, multiple joint pain, facial puffiness, and blackish discolouration of skin over the last 4 months. Blood investigations demonstrated autoantibodies positive for overlap syndrome. She was managed with hydroxychloroquine, mycophenolate mofetil and steroids. This case report highlights the importance of early diagnosis and treatment of this rare entity for better patient outcomes.

Keywords

antibodies; case reports; inflammation; systemic sclerosis.

Benign acute children myositis: 5 years experience in a tertiary care pediatric hospital

Benign acute childhood myositis (BACM) is a self-limited childhood illness, and viral infections mainly cause it. Clinical and laboratory alterations usually normalize rapidly; generally, the only medical intervention required is supportive (hydration and analgesic medication). The low awareness about BACM often led to delayed diagnosis and unneeded ancillary investigations. This study aims to better characterize the clinical and laboratory features of BACM to improve the diagnostic process and inpatient and outpatient management. We conducted a retrospective study selecting all children admitted to Meyer's Children's Hospital-IRCCS (Florence, Italy) with a diagnosis of BACM over the last 5 years, both those visited at Emergency Department (ED) and those admitted to the Pediatric Unit. Clinical, laboratory, and instrumental data were collected from electronic clinical records and analyzed. Overall, sixty-five patients were enrolled; 49 children were visited and discharged directly from ED, whereas 16 were admitted in the Pediatric or Neurologic Wards. The median age was 6.56 years (IQR 4.9-9.1). Male gender (66.1%) and Caucasian ethnicity (70%) were prevalent. Most patients were admitted during winter, and a second peak was found in autumn. All patients had bilateral calf pain, most of them (87.7%) associated with asthenia and refuse to walk (93.8%). Prodromal symptoms were fever (75.3%), cough (32.3%), coryza (26.1%), sore throat (26.1%), and vomiting (15.3%). The median value of CPK was 1827 U/L (IQR 915.5-2462) at peak. CPK median time to normalization was 7 days (IQR 7-8.5) from the nadir. Influenza B was the virus most frequently BACM associated, followed by Influenza A; a novel association with Sars-CoV-2 has been detected. Two patients had pathogenic variants at the Next Generation Sequencing myopathies panel.    Conclusion: School-aged children admitted to the hospital with walking difficulty and myalgia, generally after an upper respiratory tract infection with a moderate CPK elevation, should remind at first of BACM. Rapid complaint resolution and biochemical markers normalization will prevent unnecessary tests and inappropriate therapies. What is Known: • BACM is a self-limited syndrome associated with acute infections. Influenza A and B viruses are the main etiological agents, but BACM may be related to many other microorganisms like Parainfluenza virus, Epstein-Barr virus, Cytomegalovirus, Human herpesvirus 6, Respiratory syncytial virus, Coxsackieviruses, Mycoplasma pneumoniae, Streptococcus pyogenes, Legionella, and Salmonella spp. • Clinical and laboratory alterations usually normalize rapidly; generally, the only medical intervention required is supportive (hydration, analgesic medication). Evolution in rhabdomyolysis and kidney damage is possible but rarely reported. What is New: • Sars-CoV-2 could be an emerging possible cause of BACM. During and after the Sars-CoV-2 outbreak, virus infection seasonality has changed, and so has BACM seasonality. • Screening tests for muscular and metabolic disorders are recommended in recurrent myositis and/or cases with marked CPK elevation (≥ 5000 U/L).

Clinical associations of patients with anti-3-hydroxy-3-methylglutaryl CoA reductase antibody-associated immune-mediated necrotising myopathy

BACKGROUND

Anti-3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) antibodies are associated with a subtype of immune-mediated necrotising myopathy (IMNM).

AIMS

To determine clinical associations of anti-HMGCR antibodies for anti-HMGCR-associated IMNM (HMGCR-IMNM) among a cohort of patients in Western Australia and to determine whether serial HMGCR antibody levels parallel disease activity.

METHODS

Adult patients with positive anti-HMGCR antibodies detected by enzyme-linked immunosorbent assay between January 2015 and November 2019 were included. Symptoms, examination findings, imaging findings and blood test results were reviewed retrospectively using patient records and laboratory database results.

RESULTS

Among 26 patients with positive anti-HMGCR antibodies, 23 were diagnosed with HMGCR-IMNM representing a positive predictive value (PPV) of 88%. Myopathy was frequently severe at diagnosis with limb weakness graded as Medical Research Council score 3 or below in 78% of patients, bulbar muscle weakness in 39% and an average creatine kinase (CK) at diagnosis of 7986 U/L. The majority (83%) required at least two therapies to maintain remission, 48% had at least one flare of disease and 57% did not achieve CK normalisation. Correlation between CK and anti-HMGCR antibody level at diagnosis was low (r = 0.04). Anti-HMGCR antibodies fell with treatment in 10 of 12 patients, but remained persistently positive in 83% of patients.

CONCLUSIONS

The PPV of anti-HMGCR antibodies for HMGCR-IMNM in this Western Australian cohort is 88%. Patients typically present with proximal limb weakness, dysphagia and markedly elevated CK, and, despite multiagent immunosuppression, a significant number of patients have evidence of persistent biochemical myositis. Anti-HMGCR antibodies did not correlate with CK levels at diagnosis.