Bilateral Facial Palsy: A Rare Presenting Symptom for Inclusion Body Myositis.

Inclusion body myositis is a common type of inflammatory myopathy among populations over the age of 50 years, classically presenting with weakness and atrophy of the forearms and quadriceps. While a third of patients may eventually present with mild facial weakness, findings of ptosis, facial palsy, or involvement of extraocular muscles are rarely, if ever, seen. The authors describe a unique case of inclusion body myositis in which a patient initially presented with bilateral severe facial palsy and exposure keratitis but minimal limb weakness. While midface weakness, unilateral lagophthalmos, and ptosis have been documented in one reported case, key presenting symptoms of bilateral facial palsy and symmetric paralytic lagophthalmos with corneal exposure have not been presented before. Therefore, this case serves as an important reminder to consider the inclusion body myositis in the differential diagnosis of bilateral facial palsy.

Imaging swallowing function and the mechanisms driving dysphagia in inclusion body myositis.

Sporadic inclusion body myositis (IBM) is a progressive condition which commonly affects patients aged above 40. IBM does not respond to immunosuppression and no proven treatments are available. Up to 80% of patients develop some degree of swallowing impairment during the disease course. Dysphagia is a source of marked morbidity in IBM and predisposes patients to life-threatening complications such as aspiration pneumonia. The pathophysiology behind dysphagia in IBM is not fully understood. Evidence from imaging demonstrates that impaired swallowing is predominantly underpinned by oropharyngeal deficits. Changes in cricopharyngeal physiology is thought to be an important factor influencing dysphagia in IBM. However, it is unclear whether this is secondary to structural changes within the cricopharyngeus itself or driven by impairment of the muscles promoting pharyngeal clearance. The approach to dysphagia in IBM patients is limited by a lack of validated instruments to reliably assess swallowing function and an absence of effective therapeutic interventions derived from controlled trials targeting dysphagia. Imaging modalities such as the video fluoroscopic swallowing study (VFSS) are commonly used to evaluate dysphagia in IBM. Whilst VFSS is a commonly used technique in clinical practice; cumulative radiation exposure with repeated testing can be a limitation. Alternative imaging techniques could be developed further as outcome measures for assessing swallowing.In this review, we provide an overview of imaging techniques used to assess swallowing and the insight provided from such investigations into the mechanisms behind dysphagia in IBM. We suggest future directions for evaluation and outcome measurement of dysphagia in this population.

Efficacy of endoscopic cricopharyngeal myotomy using a curved rigid laryngoscope in patients with sporadic inclusion body myositis: four retrospective case reviews.

Sporadic inclusion body myositis (s-IBM) is an acquired degenerative inflammatory myopathy that leads to slowly progressive muscle weakness and atrophy of the limbs, face, and pharynx. Owing to the slow progression of the disease, the indications for surgical intervention remain unclear. Herein, we retrospectively reviewed the records of four patients with s-IBM who had undergone cricopharyngeal myotomy for severe dysphagia at our institution between 2016 and 2021. Among these, one patient underwent transcervical cricopharyngeal myotomy and laryngeal suspension, as videofluoroscopic examination of swallowing revealed poor laryngeal elevation. The remaining three patients underwent endoscopic cricopharyngeal myotomy using a curved rigid laryngoscope. Preoperatively, the mean Hyodo score was 8 points (range: 6-10) using a flexible endoscope. The mean surgical duration was 104 min, and no severe complications were observed. Postoperatively, all patients achieved improvement in swallowing function and food intake. Moreover, swallowing function was maintained in all four patients even 6-12 months postoperatively. Cricopharyngeal myotomy may be a safe surgical procedure with the potential to improve swallowing function, and a Hyodo score of 6 may be considered a surgical indication for cricopharyngeal myotomy in patients with s-IBM.

Update on the evaluation and management of dysphagia in sporadic inclusion body myositis.

PURPOSE OF REVIEW: Dysphagia is a common symptom of sporadic inclusion body myositis (IBM), affecting disease trajectory and patient quality-of-life. Despite this, it is considerably understudied. The purpose of this review is to summarize current evidence related to the evaluation and management of dysphagia in IBM. We highlight a patient case involving a multidisciplinary management approach, and we encourage continued exploration of exercises for delaying progression and improving impairments in patients with IBM and dysphagia. RECENT FINDINGS: Recent investigations confirm that dysphagia in IBM is a debilitating and complex symptom that warrants timely evaluation and management. Further, they highlight the lack of validation of standardized swallowing-related metrics specifically for IBM and the limited evidence supporting a consensus of management approaches. Small scale research and clinical anecdotal data support a multidisciplinary and multipronged patient-centered approach, including rehabilitative exercise protocols, for dysphagia management in IBM. SUMMARY: A paucity exists in the literature to effectively guide clinical decision-making for patients with IBM and dysphagia. Given this, it is our belief that a careful multidisciplinary and multipronged patient-centered approach is critical for dysphagia management in IBM. Prospective, longitudinal research on the underlying mechanisms of swallowing dysfunction using advanced and validated swallowing-related outcome measures is urgently needed.

Myasthenia gravis with inclusion body myositis: A case report.

We present the case of a 75-year-old man diagnosed with myasthenia gravis (MG) based on lower leg weakness and ptosis for the past 2 months before admission to our hospital. The patient was anti-acetylcholine receptor antibody-positive at admission. He was treated with pyridostigmine bromide and prednisolone, which improved the ptosis, but the lower leg muscle weakness remained. An additional lower leg magnetic resonance imaging examination suggested myositis. Inclusion body myositis (IBM) was diagnosed after a subsequent muscle biopsy. Although MG is often associated with inflammatory myopathy, IBM is rare. There is no effective treatment for IBM, but various treatment possibilities have recently been proposed. This case emphasises that myositis complications, including IBM, should be considered when elevated creatine kinase levels are observed and conventional treatments do not address chronic muscle weakness.

Diagnosing and managing dysphagia in inclusion body myositis: a systematic review.

OBJECTIVES: Dysphagia is a common debilitating clinical feature of IBM. However, the impact of dysphagia in IBM has been historically overlooked. This study aimed to identify, evaluate and summarize the evidence regarding the assessment and management of dysphagia in persons with IBM undergoing treatment. METHODS: A systematic review was conducted using a multiengine search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Eligible studies had to employ an intervention for persons with IBM, report a swallowing outcome and be published in English. Quality assessments of the eligible studies were performed. RESULTS: Of 239 studies found, 19 met the inclusion criteria. One study was rated as 'fair' and the rest as 'poor' quality, particularly due to the lack of published and validated swallowing assessment procedures and outcome measures. Cricopharyngeal (CP) dysfunction (12/19) was the most commonly reported swallowing abnormality. Interventions for disease management included pharmacological agents (10/19), followed by surgical (3/19), behavioral (1/19) and combined approaches (5/19). Interventions with immunosuppressants, botulinum toxin injection, balloon dilation and/or CP myotomy led to mixed and transient benefits. Few studies examining statins or behavioral therapies (primarily focused on respiratory function) showed no effects for dysphagia. CONCLUSION: Various interventions have been reported to temporarily improve dysphagia in persons with IBM. However, these findings are based on limited and overall low-quality evidence. This study cautions against the generalization of these findings and emphasizes the need for further systematic research to improve the diagnosis and management of dysphagia in IBM.

Clinical characteristics of dysphagic inclusion body myositis.

This study aimed to characterize dysphagic patients with inclusion body myositis (IBM) with cricopharyngeal bar (CPB) (n = 17; IBM-CPB(+)) by comparing their swallowing function and muscle magnetic resonance imaging data with IBM patients without CPB (n = 28; IBM-CPB(-)). IBM-CPB(+) patients were older at diagnosis and had more frequent obstruction-related dysphagia and stronger knee extension than IBM-CPB(-) patients. IBM-CPB(+) patients also had less intramuscular fatty infiltration than IBM-CPB(-) patients on T1-weighted magnetic resonance images of the rectus femoris (2.6% versus 10.3%, p < 0.05), vastus lateralis (27.8% versus 57.1%, p < 0.01), vastus intermedius (17.6% versus 43.5%, p < 0.01), vastus medialis (14.1% versus 39.1%, p < 0.01), deltoid (5.5% versus 18.7%, p < 0.05), biceps (6.6% versus 21.1%, p < 0.001), and triceps (12.9% versus 33.0%, p < 0.05). These findings suggest that IBM-CPB(+) patients were older, frequently exhibited obstruction-related dysphagia, had stronger knee extension, and had less fatty infiltration of the limb muscles compared to IBM-CPB(-) patients, and provide valuable information on the clinical subset of IBM-CBP(+) patients in order to expand the knowledge of the clinical heterogeneity in IBM.

Macroglossia in rapidly progressive inclusion body myositis.

Inclusion body myositis (IBM) is a refractory muscle disease characterized by inflammatory and degenerative features in myofibers. Macroglossia is common in systemic amyloid light chain amyloidosis; however, no reports have been published on patients with IBM. We encountered a female patient with clinicopathologically defined IBM who exhibited relatively rapid progression of dysphagia, gait disturbance, and macroglossia. Muscle biopsy demonstrated endomysial mononuclear inflammatory infiltrates, fiber necrosis and regeneration with rimmed vacuoles, and sarcoplasmic inclusions of p62. Tongue biopsy demonstrated fiber degeneration with fatty replacement and fibrosis, nonnecrotic fibers surrounded and invaded by mononuclear cells, and sarcoplasmic dotlike inclusions of p62. Based on the parotid gland, lip, and muscle biopsy, she was diagnosed as having IBM with Sjögren's syndrome. She was treated with steroid pulse and intravenous immunoglobulin therapy followed by oral administration of prednisolone, which resulted in temporary clinical improvement. Macroglossia might be an indicator of immunotherapy effectiveness.

Evidence of nerve hypertrophy in patients with inclusion body myositis on lower limb MRI.

INTRODUCTION/AIMS: Inclusion body myositis (IBM) is a myopathic condition but in some patients has been associated with an axonal length-dependent polyneuropathy. In this study, we quantified the cross-sectional area of the sciatic and tibial nerves in patients with IBM comparing with Charcot-Marie-Tooth disease type 1A (CMT1A) and healthy controls using magnetic resonance neurography (MRN). METHODS: MRN of the sciatic and tibial nerves was performed at 3T using MPRAGE and Dixon acquisitions. Nerve cross-sectional area (CSA) was measured at the mid-thigh and upper third calf regions by an observer blinded to the diagnosis. Correlations were performed between these measurements and clinical data. RESULTS: A total of 20 patients with IBM, 20 CMT1A and 29 healthy controls (age- and sex-matched) were studied. Sciatic nerve CSA was significantly enlarged in patients with IBM and CMT1A compared to controls (sciatic nerve mean CSA 62.3 ± 22.9 mm2 (IBM) vs. 35.5 ± 9.9 mm2 (controls), p < 0.001; and 96.9 ± 35.5 mm2 (CMT1A) vs. 35.5 ± 9.9 mm2 (controls); p < 0.001). Tibial nerve CSA was also enlarged in IBM and CMT1 patients compared to controls. DISCUSSION: MRN reveals significant hypertrophy of the sciatic and tibial nerves in patients with IBM and CMT1A compared to controls. Further studies are needed to correlate with neurophysiological measures and assess whether this finding is useful diagnostically.

Impact of dysphagia and its severity on long-term survival and swallowing function outcomes in patients with idiopathic inflammatory myopathies other than inclusion body myositis.

OBJECTIVE: To investigate the impact of dysphagia on long-term survival and swallowing function outcomes in patients with idiopathic inflammatory myopathy other than inclusion body myositis. METHODS: We retrospectively evaluated consecutive patients with idiopathic inflammatory myopathy other than inclusion body myositis to investigate the impact of dysphagia and its severity assessed using the Food Intake LEVEL Scale on survival and swallowing function outcomes. Time-to-event analyses were used, including Kaplan-Meier curves with log-rank (trend) test, cumulative incidence with Gray's test, and Cox proportional hazards models. RESULTS: Of the 254 patients, 26 were dysphagic, including eight severe (Food Intake LEVEL Scale [FILS] score 2, 3) and six most severe (FILS score 1) cases; 210 were non-dysphagic, and 18 were indeterminate cases. During the 5 years after myositis diagnosis, 15 (57.7%) dysphagic and 31 (14.8%) non-dysphagic patients died, and dysphagic patients had significantly shorter survival. However, multivariate analysis showed that shorter survival was significantly associated with baseline age-adjusted Charlson Comorbidity Index (hazard ratio [HR] 1.57, 95% confidence interval [CI] 1.36-1.82]), but not with dysphagia (HR 1.46, 95% CI 0.69-3.10). Dysphagia severity was significantly associated with delayed recovery of dysphagia. In 20 non-severe or severe dysphagic cases, 19 restored swallowing function within 1 year. The most severe cases had a significantly higher cumulative probability of death before recovery from dysphagia than severe cases. CONCLUSION: The poor survival of dysphagic myositis patients was largely confounded by advanced age and comorbid malignancies. However, patients with the most severe dysphagia had a significantly worse swallowing function and survival prognosis than those with milder dysphagia.

Sirolimus leads to rapid and sustained clinical improvement of motor deficits in a patient with inclusion body myositis.

BACKGROUND AND PURPOSE: To provide further evidence for sirolimus, a mammalian target of rapamycin inhibitor, as a treatment strategy for patients with inclusion body myositis (IBM). METHODS: We acquired longitudinal clinical data and immunological assessments of CD8+ T-cell subsets in peripheral blood for evaluation of potential anti-inflammatory treatment effects of sirolimus. RESULTS: Therapy with sirolimus 2 mg/day by mouth led to rapid and sustained clinical improvement of motor symptoms for an observation period of more than 1 year. Treatment was well tolerated, with no occurrence of adverse effects. We did not observe a meaningful alteration of CD8+ T-cell subsets in our patient after 9 and 12 months compared to baseline. CONCLUSIONS: The significant and persistent clinical improvement highlights the use of sirolimus as a potential treatment option in patients with IBM. In light of the lack of immunological treatment effects observed for cytotoxic CD8+ T cells, further studies should investigate the potential myoprotective effects of sirolimus.

Severe cardiomyopathy associated with the VCP p.R155C and c.177_187del MYBPC3 gene variants.

Inclusion Body Myopathy, Paget's Disease of Bone, with Frontotemporal Dementia is a progressive autosomal dominant disease that affects the ubiquitin-proteasome complex, that is caused by variants in the Valosin Containing Protein (VCP) gene. We report the first case of concurrent pathogenic variants in both MYBPC3 and VCP that led to earlier onset of congestive heart failure with features of dilated cardiomyopathy. Cardiomyopathy has previously been associated with VCP inclusion body myopathy mostly at an advanced stage of the disease. Due to acute onset of cardiomyopathy in a previous asymptomatic individual, a cardiomyopathy gene panel was obtained which revealed an additional c.177_187del variant of the MYBPC3 gene. We report a first case of concurrent pathogenic variants in both c.177_187del gene of MYBPC3 and p.R155C VCP that led to earlier onset and a more severe form of the cardiomyopathy.

Botulinum toxin treatment improves dysphagia in patients with oculopharyngeal muscular dystrophy and sporadic inclusion body myositis.

OBJECTIVE: Dysphagia can be troublesome in sporadic inclusion body myositis (sIBM) and oculopharyngeal muscular dystrophy (OPMD), but no established treatment exists. Cricopharyngeal muscle botulinum toxin injection has at case level been reported to be effective. We evaluated safety and efficacy of botulinum toxin injections in the cricopharyngeal muscle in patients with dysphagia due to sIBM or OPMD. METHODS: Participants were included from our outpatient clinic. Cricopharyngeal constriction was confirmed by laryngoscopy. After EMG confirmation of needle placement in the cricopharyngeal muscle, botulinum toxin A was injected in awake patients. An individualized dose of 5-10 units of botulinum toxin A was applied initially and titrated up a maximum of 3 times. Outcome measures were change in dysphagia questionnaire, timed cold-water swallow test and subjective dysphagia status (worse, unchanged, improved). Due to the need for individualized dosing and a limited number of available patients, an uncontrolled, un-blinded design was used. RESULTS: Thirteen patients, 3 with OPMD, received at least 1 injection. In the dysphagia questionnaire, all but 2 subjects, none with subjective worsening, improved (p < 0.001). Subjectively, seven felt an improvement, 4 no change and 2 a worsening. No overall change was seen the timed cold-water swallow test. No serious adverse events were observed. CONCLUSION: Botulinum toxin injection of the cricopharyngeal muscle in patients with OPMD and sIBM had a beneficial effect on dysphagia in most of the treated patients. Two of 13 patients experienced a temporary worsening not reflected in dysphagia score. Limitations are the un-blinded and un-randomized design and subjective assessments methods. PROSPECTIVE TRIAL REGISTRATION: EudraCT-number: 2014-002210-23.

Temporomandibular Disorders and Oral Features in Idiopathic Inflammatory Myopathies (IIMs) Patients: An Observational Study.

Aim: Inflammatory idiopathic myopathies (IIMs) are inflammatory processes affecting skeletal musculature and extramuscular organs. Temporomandibular disorders (TMD) involve jaw muscles and temporomandibular joint. The aim of this observational study was to investigate the prevalence of the main TMD symptoms and signs as well as oral implications in IIM patients. Methods: The study group included 54 patients (42 women and 12 men), 22 of whom affected by dermatomyositis (DM), 29 by polymyositis (PM) and 3 by inclusion body myositis (IBM). A group of 54 patients not affected by this disease, served as CG. Oral and TMD signs and symptoms were evaluated by means of a questionnaire and through clinical examination. Results: About oral symptoms, the study group complained more frequently dysgeusia, with loss of taste or unpleasant taste (p<0.0001) and feeling of burning mouth (9.4% versus 0 controls). Xerostomia was more prevalent in the study group respect to the CG (p<0.0001). Dysphagia was reported by 48.1% of IIM patients while was absent in CG (p<0.0001). About oral signs, cheilitis (p<0.05) and oral ulcers (p<0.05) were significantly more frequent in CG. As regard to TMD symptoms, arthralgia and tinnitus didn't showed significant differences between the two groups, while neck/shoulders and masticatory muscle pain was significantly more referred in IIM patients than in the CG (p<0.05). About TMJ signs, sounds were overlapping in the two groups: click=11.1% in both IIM patients and CG (p>0.05), crepitation in 11.1% of IIM and 9.3% of controls (p>0.05). No significant difference was detected about deflection (9.3%, p>0.05), while deviation was wider in CG (p<0.05). Active opening and lateralities showed no significant differences, while endfeel was significantly increased in IIM group for a higher presence of muscular contracture. Bruxism was present only in CG. Conclusion: The data collected from this observational study seem to support the existence of a relationship between the prevalence of TMD symptoms and signs as well as oral features in patients with myositis. A remarkable reduction of salivary flow and dysphagia were more frequent and severe in IIM patients, as well as muscle contracture and myofacial pain evoked by palpation, this result being highly significant.

Interstitial amyloidosis in sporadic inclusion body myositis.

INTRODUCTION/AIMS: Intracellular congophilic inclusions within muscle fibers, although nonspecific, are one of the pathological hallmarks of sporadic inclusion body myositis (sIBM). Extracellular amyloid deposits in muscle, on the other hand, are the canonical findings of amyloid myopathies, which occur with or without systemic amyloidosis. METHODS: We reviewed the muscle biopsy database (1998-2020) to identify sIBM patients with extracellular amyloid deposits. Clinical and laboratory data were reviewed. RESULTS: We identified five sIBM patients (three clinicopathologically defined and two clinically defined) with extracellular amyloid deposits in muscle. Mean age at diagnosis was 74.8 y (range, 68-84 y). All patients had a typical sIBM pattern of weakness without associated sensory or autonomic symptoms. None had electrophysiological evidence of peripheral neuropathy. Only one patient had a monoclonal gammopathy (immunoglobulin M-lambda, IgM-λ) with normal bone marrow biopsy. This patient with monoclonal gammopathy and three other patients underwent abdominal fat pad aspirate and were negative for amyloid. Cardiac evaluation was unrevealing in the four patients tested. Three patients without monoclonal gammopathy had normal transthyretin gene sequencing and inconclusive mass spectrometry-based analysis. The patient with monoclonal gammopathy died of pneumosepsis 5 y after diagnosis and autopsy revealed multi-organ transthyretin amyloidosis. DISCUSSION: Detection of extracellular amyloid deposition in muscle should trigger an aggressive search for systemic amyloidosis independently from other associated myopathological abnormalities. Amyloid subtyping is crucial for early therapy and mortality prevention. An isolated monoclonal gammopathy should not halt a search for non-hematological causes of systemic amyloidosis.

Tendon Transfers for the Treatment of Finger Flexion Weakness in a Patient With Inclusion Body Myositis: A Case Report.

CASE: We describe a 71-year-old patient with inclusion body myositis (IBM), characterized by progressive atrophy and weakness in his left upper extremity. This patient underwent extensor carpi radialis longus to flexor pollicis longus and brachioradialis to flexor digitorum profundus tendon transfers in the left upper extremity to reduce IBM-related functional deficits. He had noticeable improvements in finger flexion after the transfers, which have been sustained for 2 years after the procedure. CONCLUSION: This case reinforces that this novel tendon transfer may be an effective treatment option to improve hand function and activities of daily living in patients with IBM.

Cricopharyngeal Myotomy in Inclusion Body Myositis: Comparison of Endoscopic and Transcervical Approaches.

OBJECTIVE: Inclusion body myositis (IBM) is a progressive inflammatory myopathy with dysphagia as a debilitating sequalae. Otolaryngologists are consulted for surgical candidacy when there are findings of cricopharyngeal dysfunction. We aim to compare transcervical cricopharyngeal myotomy (TCPM) versus endoscopic cricopharyngeal myotomy (ECPM) in the IBM population with particular focus on objective swallow study outcomes, complications, and recurrence rates. METHODS: A retrospective cohort study was performed on IBM patients who underwent TCPM or ECPM (1981-2020) in the Department of Otolaryngology at a tertiary academic center with a high volume IBM referral base. Videofluoroscopic swallow studies, Eating Assessment Tool (EAT-10), Reflux Symptom Index (RSI), and Functional Outcome Swallowing Scale (FOSS) were collected at preoperative and follow-up visits. Baseline patient characteristics, intraoperative data, and postoperative course were recorded. RESULTS: Forty-one patients were identified (18 TCPM; 23 ECPM). There was no significant difference in the recurrence rates, complications, hospitalization length, operative time, or return to preoperative diet between approaches. For the 12 patients (11 ECPM; 1 TCPM) that had subjective swallow data, there was a statistically significant difference in the pre and postoperative scores for EAT-10, RSI, and FOSS (P < .05). There was a statistically significant improvement in the degree of narrowing between pre and postoperative imaging for both approaches (P < .05). CONCLUSION: Both TCPM and ECPM are safe approaches for the management of dysphagia in patients with IBM with objective evidence of cricopharyngeal dysfunction. Cricopharyngeal myotomy is a durable technique that has demonstrated improved subjective and objective outcomes in this patient population. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:E2426-E2431, 2021.

Efficacy and Safety of Bimagrumab in Sporadic Inclusion Body Myositis: Long-term Extension of RESILIENT.

OBJECTIVE: To assess long-term (2 years) effects of bimagrumab in participants with sporadic inclusion body myositis (sIBM). METHODS: Participants (aged 36-85 years) who completed the core study (RESILIENT [Efficacy and Safety of Bimagrumab/BYM338 at 52 Weeks on Physical Function, Muscle Strength, Mobility in sIBM Patients]) were invited to join an extension study. Individuals continued on the same treatment as in the core study (10 mg/kg, 3 mg/kg, 1 mg/kg bimagrumab or matching placebo administered as IV infusions every 4 weeks). The co-primary outcome measures were 6-minute walk distance (6MWD) and safety. RESULTS: Between November 2015 and February 2017, 211 participants entered double-blind placebo-controlled period of the extension study. Mean change in 6MWD from baseline was highly variable across treatment groups, but indicated progressive deterioration from weeks 24-104 in all treatment groups. Overall, 91.0% (n = 142) of participants in the pooled bimagrumab group and 89.1% (n = 49) in the placebo group had ≥1 treatment-emergent adverse event (AE). Falls were slightly higher in the bimagrumab 3 mg/kg group vs 10 mg/kg, 1 mg/kg, and placebo groups (69.2% [n = 36 of 52] vs 56.6% [n = 30 of 53], 58.8% [n = 30 of 51], and 61.8% [n = 34 of 55], respectively). The most frequently reported AEs in the pooled bimagrumab group were diarrhea 14.7% (n = 23), involuntary muscle contractions 9.6% (n = 15), and rash 5.1% (n = 8). Incidence of serious AEs was comparable between the pooled bimagrumab and the placebo group (18.6% [n = 29] vs 14.5% [n = 8], respectively). CONCLUSION: Extended treatment with bimagrumab up to 2 years produced a good safety profile and was well-tolerated, but did not provide clinical benefits in terms of improvement in mobility. The extension study was terminated early due to core study not meeting its primary endpoint. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT02573467. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with sIBM, long-term treatment with bimagrumab was safe, well-tolerated, and did not provide meaningful functional benefit. The study is rated Class IV because of the open-label design of extension treatment period 2.