The impact of pain on daily activities in patients with idiopathic inflammatory myopathies: Report from the OMERACT myositis working group.

BACKGROUND: International focus groups with patients with idiopathic inflammatory myopathies (IIM) conducted by the OMERACT Myositis Working Group over the years demonstrated the pain as an important symptom experienced by these patients. In this study, we aimed to examine the frequency and degree of pain interference, the aspects of daily life impacted by pain, and the factors associated with pain interference in adults with IIM. METHODS: This was a prospective observational study with two visits. The patients who fulfilled the probable/definite IIM (ACR/EULAR Myositis Classification Criteria) were enrolled. Pain interference was assessed with PROMIS pain interference form (6a). Myositis core set measures and PROMIS fatigue (7a) and physical function (8b) were obtained at both visits. Logistic regression and linear mixed models were performed to assess the association between pain interference and other parameters. RESULTS: A total of 129 patients with IIM (60 % females) were recruited from U.S., South Korea, Netherlands, Sweden, and Australia. Approximately 71 % reported pain interference. The patients in the greater pain interference group were more likely to be female, had significantly worse patient/physician global disease activity, fatigue, and physical function than those in the lower pain interference group. The most commonly impacted life aspect was household chores. Manual muscle testing, patient/physician global disease activity, fatigue, and physical function were all significantly associated with pain interference score >60. CONCLUSION: The majority of the patients with IIM experience the impact of pain on their daily activities, particularly household chores. Myositis disease activity, duration, and subtype could be associated with greater pain interference.

Correction: Testosterone treatment combined with exercise to improve muscle strength, physical function and quality of life in men affected by inclusion body myositis: A randomised, double-blind, placebo-controlled, crossover trial.

[This corrects the article DOI: 10.1371/journal.pone.0283394.].

Identification of distinct immune signatures in inclusion body myositis by peripheral blood immunophenotyping using machine learning models.

Objective: Inclusion body myositis (IBM) is a progressive late-onset muscle disease characterised by preferential weakness of quadriceps femoris and finger flexors, with elusive causes involving immune, degenerative, genetic and age-related factors. Overlapping with normal muscle ageing makes diagnosis and prognosis problematic. Methods: We characterised peripheral blood leucocytes in 81 IBM patients and 45 healthy controls using flow cytometry. Using a random forest classifier, we identified immune changes in IBM compared to HC. K-means clustering and the random forest one-versus-rest model classified patients into three immunophenotypic clusters. Functional outcome measures including mTUG, 2MWT, IBM-FRS, EAT-10, knee extension and grip strength were assessed across clusters. Results: The random forest model achieved a 94% AUC ROC with 82.76% specificity and 100% sensitivity. Significant differences were found in IBM patients, including increased CD8+ T-bet+ cells, CD4+ T cells skewed towards a Th1 phenotype and altered γδ T cell repertoire with a reduced proportion of Vγ9+Vδ2+ cells. IBM patients formed three clusters: (i) activated and inflammatory CD8+ and CD4+ T-cell profile and the highest proportion of anti-cN1A-positive patients in cluster 1; (ii) limited inflammation in cluster 2; (iii) highly differentiated, pro-inflammatory T-cell profile in cluster 3. Additionally, no significant differences in patients' age and gender were detected between immunophenotype clusters; however, worsening trends were detected with several functional outcomes. Conclusion: These findings unveil distinct immune profiles in IBM, shedding light on underlying pathological mechanisms for potential immunoregulatory therapeutic development.

Consumer-driven evaluation of assistive technology usage and perceived value in people with myositis in Australia.

INTRODUCTION: Idiopathic inflammatory myopathies (known as 'myositis') are a group of rare sporadic inflammatory muscle disorders that significantly impact function and quality of life. There are no standardised approaches in the use of assistive technologies in myositis. This study was initiated to investigate current use and perceived value of assistive technology (AT) by people with myositis. METHODS: A cross-sectional online questionnaire (Qualtrics) was designed to capture information regarding AT use and perceived value and demographic information from people with myositis across Australia. The questionnaire was distributed via the Myositis Association of Australia and specialist myositis clinics. Participants were asked to identify which AT items they owned and how frequently the item was used and to rate the 'usefulness' of those items. Information was also collected on participants' engagement with health professionals regarding assistive technologies. CONSUMER AND COMMUNITY INVOLVEMENT: Consumer involvement via the Myositis Research Consumer Panel identified a knowledge gap regarding AT. The questionnaire was designed with consumer input and review. RESULTS: One hundred two people (102) with myositis completed the questionnaire. One hundred (100) participants owned at least one AT device, with a median of 12.5 items and a maximum of 65 items. The most used devices were associated with toileting, personal care and mobility. Participants rated AT devices relating to environmental support, sleeping, seating and body support as most useful. There was a positive correlation between disease duration and number of devices used (r2 = 0.248, p = 0.012). Majority of participants (75.5%) were interested in talking to health professionals about AT; however, only 50% had done so. CONCLUSION: AT device usage is high among people with myositis, with most items deemed to be useful. Greater occupational therapy input into recommendations and potential funding options may improve knowledge and access to AT.

Performance of the 2017 EULAR/ACR Classification Criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: a scoping review.

The 2017 EULAR/ACR classification criteria for adult/juvenile idiopathic inflammatory myopathies (IIM) were established using a data-driven approach by an international group of myositis experts to allow classification of IIM and its major subtypes. Since their publication, the performance of the criteria has been tested in multiple cohorts worldwide and significant limitations have been identified. Moreover, the understanding and classification of IIM have evolved since 2017. This scoping review was undertaken as part of a large international project to revise the EULAR/ACR criteria and aims to i) summarise the evidence from the current literature on the performance characteristics of the 2017 EULAR/ACR classification criteria in various cohorts and IIM subtypes, and ii) delineate the factors that need to be considered in the revision of the classification criteria. A systematic search of Medline (via PubMed), Cumulative Index to Nursing and Allied Health Literature, and conference abstract archives was conducted independently by three investigators for studies on the EULAR/ACR criteria published between October 2017 and January 2023. This scoping review of 19 articles and 13 abstracts revealed overall good performance characteristics of the EULAR/ACR criteria for IIM, yet deficiencies in lack of inclusion of certain IIM subtypes, such as immune mediated necrotising myopathy, amyopathic dermatomyositis, antisynthetase syndrome and overlap myositis. Published modifications that may improve the performance characteristics of the criteria for classification of IIM subtypes were also summarised. The results of this review suggest that a revision of the EULAR/ACR criteria is warranted.

Does inspiratory muscle training improve lung function and quality of life in people with inclusion body myositis? A pilot study.

Inclusion body myositis is the most common acquired myositis in adults, predominantly weakening forearm flexor and knee extensor muscles. Subclinical respiratory muscle weakness has recently been recognised in people with inclusion body myositis, increasing their risk of respiratory complications. Inspiratory muscle training, a technique which demonstrates efficacy and safety in improving respiratory function in people with neuromuscular disorders, has never been explored in those with inclusion body myositis. In this pilot study, six adults with inclusion body myositis (age range 53 to 81 years) completed eight weeks of inspiratory muscle training. Measures of respiratory function, quality of life, sleep quality and a two-minute walk test were performed pre and post-intervention. All participants improved their respiratory function, with maximal inspiratory pressure, sniff nasal inspiratory pressure and forced vital capacity increasing by an average of 50 % (p = .002), 43 % (p = .018) and 13 % (p = .003) respectively. No significant change was observed in quality of life, sleep quality or two-minute walk test performance. No complications occurred due to inspiratory muscle training This pilot study provides the first evidence that inspiratory muscle training may be safe and effective in people with Inclusion Body Myositis, potentially mitigating the complications of poor respiratory function.

Clinical prognostic factors predicting survival of motor neuron disease patients with gastrostomy: A retrospective analysis.

INTRODUCTION/AIMS: Enteral feeding via gastrostomy is a key intervention to prevent significant weight loss in Motor Neuron Disease (MND). The aim of this study was to explore demographic, clinical, and nutritional factors associated with survival time in MND patients with gastrostomy. METHODS: The retrospective study analyzed 94 MND patients (n = 58 bulbar-onset and n = 36 limb-onset) who underwent gastrostomy between 2015 and 2021. The primary outcome was the survival time from gastrostomy insertion to death. Independent variables of interest explored were: age at gastrostomy insertion, disease onset type, known genetic cause, use of riluzole, non-invasive ventilation (NIV) use, forced vital capacity prior to gastrostomy, weight loss from diagnosis to gastrostomy insertion, and body mass index (BMI) at the time of gastrostomy insertion. RESULTS: The median survival time from gastrostomy to death was 357 days (± 29.3, 95%CI: 299.5, 414.5). Kaplan-Meier method and log-rank test revealed patients with lower body mass index <18.5 kg/m2 at the time of gastrostomy insertion (p = .023) had shorter survival. Cox proportional hazards model with multivariable adjustment revealed that older age (p = .008), and greater weight loss from diagnosis to gastrostomy (p = .003) were associated with shorter survival time post gastrostomy. Limb onset (p = .023), NIV use not being required (p = .008) and daily NIV use when required and tolerated (p = .033) were associated with longer survival. DISCUSSION: Preventing or minimizing weight loss from MND diagnosis and encouraging NIV use when clinically indicated are modifiable factors that may prolong the survival of MND patients with gastrostomy.

Current myositis clinical trials and tribulations.

With improved understanding of disease pathogenesis and availability of outcome measures, there has been a remarkable increase in the number of therapeutic clinical trials in idiopathic inflammatory myopathies (myositis) over the last three years reaching as many as five trials per site. These trials share similar design and inclusion/exclusion criteria resulting in a competitive clinical trial landscape in myositis. While these are exciting times for the myositis field, we have a number of concerns about the design and conduct of the myositis trials. These include competitive landscape, lengthy placebo arms, underrepresentation of minority groups among participants, use of patient reported outcome measures with limited/no data on validity in myositis, antiquated disease classification criteria, and unclear performance of the ACR/EULAR Myositis Response Criteria in skin-predominant patients despite inclusion of these patients in trials. In this viewpoint, we further discuss these concerns and offer potential solutions such as including patient perspectives in the trial design and adoption of innovative frameworks.

The longitudinal study of muscle changes with ultrasound: differential changes in idiopathic inflammatory myopathy subgroups.

OBJECTIVES: We investigated shear wave elastography (SWE), B mode US and power Doppler (PDUS) as imaging biomarkers for longitudinal follow-up in idiopathic inflammatory myopathy (IIM), with a particular focus on immune-mediated necrotizing myopathy (IMNM) and DM. METHODS: Participants had serial SWE, PDUS on the deltoid (D) and vastus lateralis (VL) muscles on four occasions at intervals of 3-6 months. Clinical assessments included manual muscle testing, and patient- and physician-reported outcome scales. RESULTS: Thirty-three participants were included: IMNM = 17, DM = 12, overlap myositis = 3, PM = 1. Twenty were in a prevalent clinic group, and 13 were recently treated cases in an incident group. Differential changes in SWS and US domains occurred with time in both the prevalent and incident groups. In the VL-prevalent subgroup, echogenicity increased over time (P = 0.040), while in the incident cases there was a trend for reduction to normal over time (P = 0.097) with treatment. Muscle bulk reduced in the D-prevalent subgroup over time (P = 0.096), suggesting atrophy. SWS also reduced in the VL-incident subgroup over time (P = 0.096), suggesting a trend towards improvement in muscle stiffness with treatment. CONCLUSION: SWE and US appear promising as imaging biomarkers for patient follow-up in IIM and indicate changes over time, especially with echogenicity, muscle bulk and SWS in the VL. Due to the limitations of the participant numbers, additional studies with a larger cohort are needed to help evaluate these US domains further and outline specific characteristics within the IIM subgroups.

High-resolution HLA genotyping in inclusion body myositis refines 8.1 ancestral haplotype association to DRB1*03:01:01 and highlights pathogenic role of arginine-74 of DRß1 chain.

OBJECTIVES: Inclusion body myositis (IBM) is a progressive inflammatory-degenerative muscle disease of older individuals, with some patients producing anti-cytosolic 5'-nucleotidase 1A (NT5C1A, aka cN1A) antibodies. Human Leukocyte Antigens (HLA) is the highest genetic risk factor for developing IBM. In this study, we aimed to further define the contribution of HLA alleles to IBM and the production of anti-cN1A antibodies. METHODS: We HLA haplotyped a Western Australian cohort of 113 Caucasian IBM patients and 112 ethnically matched controls using Illumina next-generation sequencing. Allele frequency analysis and amino acid alignments were performed using the Genentech/MiDAS bioinformatics package. Allele frequencies were compared using Fisher's exact test. Age at onset analysis was performed using the ggstatsplot package. All analysis was carried out in RStudio version 1.4.1717. RESULTS: Our findings validated the independent association of HLA-DRB1*03:01:01 with IBM and attributed the risk to an arginine residue in position 74 within the DRß1 protein. Conversely, DRB4*01:01:01 and DQA1*01:02:01 were found to have protective effects; the carriers of DRB1*03:01:01 that did not possess these alleles had a fourteenfold increased risk of developing IBM over the general Caucasian population. Furthermore, patients with the abovementioned genotype developed symptoms on average five years earlier than patients without. We did not find any HLA associations with anti-cN1A antibody production. CONCLUSIONS: High-resolution HLA sequencing more precisely characterised the alleles associated with IBM and defined a haplotype linked to earlier disease onset. Identification of the critical amino acid residue by advanced biostatistical analysis of immunogenetics data offers mechanistic insights and future directions into uncovering IBM aetiopathogenesis.

A longitudinal study using B mode ultrasound and power Doppler as monitoring imaging tools in inclusion body myositis.

OBJECTIVES: There is growing interest in ultrasound (US) as an outcome measure in IBM. Our study aimed to determine the ability of B mode US and power Doppler (PD) to detect changes in affected muscles over time and if US domains correlate with disease progression. METHODS: Participants attended on four occasions over a median follow-up period of 26 months. All completed a patient self-reported health assessment questionnaire (HAQ), patient visual analogue scale (pVAS), manual muscle testing (MMT), and US (fascial thickness-FT, muscle bulk, echogenicity, and PD) on deltoid and vastus lateralis (VL) muscles at each visit. RESULTS: This longitudinal observational study had 35 participants: 21 (60%) males, median age 70 (IQR (64-76), and the majority (85.7%) not on immunosuppression. When analysed for sex differences at baseline, males had lower FT-VL (p=0.018) and higher muscle bulk (p=0.002) than females. Only FT-deltoid (p<0.001) increased significantly over time with follow-up. When participants were stratified into progressors and non-progressors, FT at baseline was lower in progressors (0.06 vs. 0.09, p=0.017), who were predominantly male. There were no significant differences in other US domains. CONCLUSIONS: Our study highlights previously unreported sex differences in US findings in IBM. Certain US domains, such as FT, showed measurable changes over time and correlated with disease progression. However, further studies with longer follow-up periods and larger patient cohorts will need to be performed to determine whether B mode US could be a useful disease outcome measure for therapeutic trials.

Old muscle, new tricks: a clinician perspective on sarcopenia and where to next.

PURPOSE OF REVIEW: This review offers a contemporary clinical approach to the recognition, prevention and management of sarcopenia, and discusses recent clinically relevant advances in the aetiopathogenesis of muscle ageing that may lead to future therapeutic targets. RECENT FINDINGS: The key recent directions for sarcopenia are in the diagnosis, understanding molecular mechanisms and management. Regarding the recognition of the condition, it has become increasingly clear that different definitions hamper progress in understanding. Therefore, the Global Leadership in Sarcopenia has been established in 2022 to develop a universally accepted definition. Moreover, substantial work is occurring to understand the various roles and contribution of inflammation, oxidative stress, mitochondrial dysfunction and metabolic dysregulation on skeletal muscle function and ageing. Finally, the role of resistance-based exercise regimes has been continually emphasised. However, the role of protein supplementation and hormone replacement therapy (HRT) are still under debate, and current clinical trials are underway. SUMMARY: With the global ageing of our population, there is increasing emphasis on maintaining good health. Maintenance of skeletal muscle strength and function are key to preventing frailty, morbidity and death.

Modelling accessibility of adult neurology care in Australia, 2020-2034.

Introduction: In 2015/2016, annual national expenditure on neurological conditions exceeded $A3 billion. However, a comprehensive study of the Australian neurological workforce and supply/demand dynamics has not previously been undertaken. Methods: Current neurological workforce was defined using neurologist survey and other sources. Workforce supply modelling used ordinary differential equations to simulate neurologist influx and attrition. Demand for neurology care was estimated by reference to literature regarding incidence and prevalence of selected conditions. Differences in supply versus demand for neurological workforce were calculated. Potential interventions to increase workforce were simulated and effects on supply versus demand estimated. Results: Modelling of the workforce from 2020 to 2034 predicted an increase in neurologist number from 620 to 89. We estimated a 2034 capacity of 638 024 Initial and 1 269 112 Review encounters annually, and deficits against demand estimated as 197 137 and 881 755, respectively. These deficits were proportionately greater in regional Australia, which has 31% of Australia's population (Australian Bureau of Statistics) but is served by only 4.1% of its neurologists as determined by our 2020 survey of Australia and New Zealand Association of Neurologists members. Nationally, simulated additions to the neurology workforce had some effect on the review encounter supply deficit (37.4%), but in Regional Australia, this impact was only 17.2%. Interpretation: Modelling of the neurologist workforce in Australia for 2020-2034 demonstrates a significant shortfall of supply relative to current and projected demand. Interventions to increase neurologist workforce may attenuate this shortfall but will not eliminate it. Thus, additional interventions are needed, including improved efficiency and additional use of support staff.

Uncovering the significance of expanded CD8+ large granular lymphocytes in inclusion body myositis: Insights into T cell phenotype and functional alterations, and disease severity.

Introduction: Inclusion body myositis (IBM) is a progressive inflammatory myopathy characterised by skeletal muscle infiltration and myofibre invasion by CD8+ T lymphocytes. In some cases, IBM has been reported to be associated with a systemic lymphoproliferative disorder of CD8+ T cells exhibiting a highly differentiated effector phenotype known as T cell Large Granular Lymphocytic Leukemia (T-LGLL). Methods: We investigated the incidence of a CD8+ T-LGL lymphoproliferative disorder in 85 IBM patients and an aged-matched group of 56 Healthy Controls (HC). Further, we analysed the phenotypical characteristics of the expanded T-LGLs and investigated whether their occurrence was associated with any particular HLA alleles or clinical characteristics. Results: Blood cell analysis by flow cytometry revealed expansion of T-LGLs in 34 of the 85 (40%) IBM patients. The T cell immunophenotype of T-LGLHIGH patients was characterised by increased expression of surface molecules including CD57 and KLRG1, and to a lesser extent of CD94 and CD56 predominantly in CD8+ T cells, although we also observed modest changes in CD4+ T cells and γδ T cells. Analysis of Ki67 in CD57+ KLRG1+ T cells revealed that only a small proportion of these cells was proliferating. Comparative analysis of CD8+ and CD4+ T cells isolated from matched blood and muscle samples donated by three patients indicated a consistent pattern of more pronounced alterations in muscles, although not significant due to small sample size. In the T-LGLHIGH patient group, we found increased frequencies of perforin-producing CD8+ and CD4+ T cells that were moderately correlated to combined CD57 and KLRG1 expression. Investigation of the HLA haplotypes of 75 IBM patients identified that carriage of the HLA-C*14:02:01 allele was significantly higher in T-LGLHIGH compared to T-LGLLOW individuals. Expansion of T-LGL was not significantly associated with seropositivity patient status for anti-cytosolic 5'-nucleotidase 1A autoantibodies. Clinically, the age at disease onset and disease duration were similar in the T-LGLHIGH and T-LGLLOW patient groups. However, metadata analysis of functional alterations indicated that patients with expanded T-LGL more frequently relied on mobility aids than T-LGLLOW patients indicating greater disease severity. Conclusion: Altogether, these results suggest that T-LGL expansion occurring in IBM patients is correlated with exacerbated immune dysregulation and increased disease burden.

Testosterone treatment combined with exercise to improve muscle strength, physical function and quality of life in men affected by inclusion body myositis: A randomised, double-blind, placebo-controlled, crossover trial.

INTRODUCTION: Inclusion body myositis (IBM) is the most commonly acquired skeletal muscle disease of older adults involving both autoimmune attack and muscle degeneration. As exercise training can improve outcomes in IBM, this study assessed whether a combination of testosterone supplementation and exercise training would improve muscle strength, physical function and quality of life in men affected by IBM, more than exercise alone. METHODS: This pilot study was a single site randomised, double-blind, placebo-controlled, crossover study. Testosterone (exercise and testosterone cream) and placebo (exercise and placebo cream) were each delivered for 12 weeks, with a two-week wash-out between the two periods. The primary outcome measure was improvement in quadriceps isokinetic muscle strength. Secondary outcomes included assessment of isokinetic peak flexion force, walk capacity and patient reported outcomes, and other tests, comparing results between the placebo and testosterone arms. A 12-month Open Label Extension (OLE) was offered using the same outcome measures collected at 6 and 12-months. RESULTS: 14 men completed the trial. There were no significant improvements in quadriceps extension strength or lean body mass, nor any of the secondary outcomes. Improvement in the RAND Short Form 36 patient reported outcome questionnaire 'emotional wellbeing' sub-category was reported during the testosterone arm compared to the placebo arm (mean difference [95% CI]: 6.0 points, [95% CI 1.7,10.3]). The OLE demonstrated relative disease stability over the 12-month period but with a higher number of testosterone-related adverse events. CONCLUSIONS: Adding testosterone supplementation to exercise training did not significantly improve muscle strength or physical function over a 12-week intervention period, compared to exercise alone. However, the combination improved emotional well-being over this period, and relative stabilisation of disease was found during the 12-month OLE. A longer duration trial involving a larger group of participants is warranted.

Provisional practice recommendation for the management of myopathy in VCP-associated multisystem proteinopathy.

Valosin-containing protein (VCP)-associated multisystem proteinopathy (MSP) is a rare genetic disorder with abnormalities in the autophagy pathway leading to various combinations of myopathy, bone diseases, and neurodegeneration. Ninety percent of patients with VCP-associated MSP have myopathy, but there is no consensus-based guideline. The goal of this working group was to develop a best practice set of provisional recommendations for VCP myopathy which can be easily implemented across the globe. As an initiative by Cure VCP Disease Inc., a patient advocacy organization, an online survey was initially conducted to identify the practice gaps in VCP myopathy. All prior published literature on VCP myopathy was reviewed to better understand the different aspects of management of VCP myopathy, and several working group sessions were conducted involving international experts to develop this provisional recommendation. VCP myopathy has a heterogeneous clinical phenotype and should be considered in patients with limb-girdle muscular dystrophy phenotype, or any myopathy with an autosomal dominant pattern of inheritance. Genetic testing is the only definitive way to diagnose VCP myopathy, and single-variant testing in the case of a known familial VCP variant, or multi-gene panel sequencing in undifferentiated cases can be considered. Muscle biopsy is important in cases of diagnostic uncertainty or lack of a definitive pathogenic genetic variant since rimmed vacuoles (present in ~40% cases) are considered a hallmark of VCP myopathy. Electrodiagnostic studies and magnetic resonance imaging can also help rule out disease mimics. Standardized management of VCP myopathy will optimize patient care and help future research initiatives.

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.