April L. McVey

CLINICAL FINDINGS IN MUSK-ANTIBODY POSITIVE MYASTHENIA GRAVIS: A U.S. EXPERIENCE

We performed a retrospective chart review on 53 muscle‐specific kinase antibody (MuSK‐Ab)‐positive myasthenia gravis (MG) patients at nine university‐based centers in the U.S. Of these, 66% were Caucasian, 85% were women, and age of onset was 9–79 years. Twenty‐seven patients were nonresponsive to anticholinesterase therapy. Myasthenia Gravis Foundation of America improvement status was achieved in 53% patients on corticosteroids, 51% with plasma exchange, and in 20% on intravenous immunoglobulin (IVIG). Thymectomy was beneficial in 7/18 patients at 3 years. Long‐term (≥3 years) outcome was very favorable in 58% of patients who achieved remission and/or minimal manifestation status. Overall, 73% improved. There was one MG‐related death. This survey reinforces several cardinal features of MuSK‐Ab‐positive MG, including prominent bulbar involvement and anticholinesterase nonresponsiveness. Facial or tongue atrophy was rare. Most patients respond favorably to immunotherapy. The best clinical response was to corticosteroids and plasma exchange, and the poorest response was to IVIG. Long‐term outcome is favorable in about 60% of cases. Muscle Nerve, 2009

Pilot trial of etanercept in the treatment of inclusion-body myositis.

Inclusion-body myositis (IBM) is an inflammatory muscle disease that has proven resistant to treatment. Tumor necrosis factor molecules have been detected in muscle biopsies from patients with IBM. Etanercept is a TNFα receptor fusion protein that binds and inactivates tumor necrosis factor. Nine patients were treated with etanercept at a dose of 25 mg, two times a week for an average of 17 ± 6.1 months. Each patient was evaluated using quantitative strength testing. Their data were compared to two different control groups. The first control group consisted of patients who participated in trials of beta-interferon-1A and had received placebo. There was no significant difference. The second control group was a natural history cohort of IBM patients. There was no statistically significant difference between the treated group and the natural history group at 6 and 12 months when looking at elbow flexors, or 6 months when looking at hand grip. In the treated patients there was a small but significant improvement (p = 0.002) in handgrip at 12 months.

Randomized double-blind study of botulinum toxin type B for sialorrhea in ALS patients

Twenty ALS patients with sialorrhea refractory to medical therapy were enrolled in this double‐blind, randomized study to receive either 2,500 U of botulinum toxin type B (BTxb) or placebo into the bilateral parotid and submandibular glands using electromyographic guidance. Patients who received BTxb reported a global impression of improvement of 82% at 2 weeks compared to 38% of those who received placebo (P < 0.05). This significant effect was sustained at 4 weeks. At 12 weeks, 50% of patients who received BTxb continued to report improvement compared to 14% of those who received placebo. There were no significant adverse events, including dysphagia, in the BTxb group, and there was no significant increase in the rate of decline of vital capacity. Muscle Nerve 39: 137–143, 2009

A genome-wide association study of myasthenia gravis

IMPORTANCE Myasthenia gravis is a chronic, autoimmune, neuromuscular disease characterized by fluctuating weakness of voluntary muscle groups. Although genetic factors are known to play a role in this neuroimmunological condition, the genetic etiology underlying myasthenia gravis is not well understood. OBJECTIVE To identify genetic variants that alter susceptibility to myasthenia gravis, we performed a genome-wide association study. DESIGN, SETTING, AND PARTICIPANTS DNA was obtained from 1032 white individuals from North America diagnosed as having acetylcholine receptor antibody-positive myasthenia gravis and 1998 race/ethnicity-matched control individuals from January 2010 to January 2011. These samples were genotyped on Illumina OmniExpress single-nucleotide polymorphism arrays. An independent cohort of 423 Italian cases and 467 Italian control individuals were used for replication. MAIN OUTCOMES AND MEASURES We calculated P values for association between 8,114,394 genotyped and imputed variants across the genome and risk for developing myasthenia gravis using logistic regression modeling. A threshold P value of 5.0×10(-8) was set for genome-wide significance after Bonferroni correction for multiple testing. RESULTS In the overall case-control cohort, we identified association signals at CTLA4 (rs231770; P=3.98×10(-8); odds ratio, 1.37; 95% CI, 1.25-1.49), HLA-DQA1 (rs9271871; P=1.08×10(-8); odds ratio, 2.31; 95% CI, 2.02-2.60), and TNFRSF11A (rs4263037; P=1.60×10(-9); odds ratio, 1.41; 95% CI, 1.29-1.53). These findings replicated for CTLA4 and HLA-DQA1 in an independent cohort of Italian cases and control individuals. Further analysis revealed distinct, but overlapping, disease-associated loci for early- and late-onset forms of myasthenia gravis. In the late-onset cases, we identified 2 association peaks: one was located in TNFRSF11A (rs4263037; P=1.32×10(-12); odds ratio, 1.56; 95% CI, 1.44-1.68) and the other was detected in the major histocompatibility complex on chromosome 6p21 (HLA-DQA1; rs9271871; P=7.02×10(-18); odds ratio, 4.27; 95% CI, 3.92-4.62). Association within the major histocompatibility complex region was also observed in early-onset cases (HLA-DQA1; rs601006; P=2.52×10(-11); odds ratio, 4.0; 95% CI, 3.57-4.43), although the set of single-nucleotide polymorphisms was different from that implicated among late-onset cases. CONCLUSIONS AND RELEVANCE Our genetic data provide insights into aberrant cellular mechanisms responsible for this prototypical autoimmune disorder. They also suggest that clinical trials of immunomodulatory drugs related to CTLA4 and that are already Food and Drug Administration approved as therapies for other autoimmune diseases could be considered for patients with refractory disease.

Phase II screening trial of lithium carbonate in amyotrophic lateral sclerosis Examining a more efficient trial design

Objective: To use a historical placebo control design to determine whether lithium carbonate slows progression of amyotrophic lateral sclerosis (ALS). Methods: A phase II trial was conducted at 10 sites in the Western ALS Study Group using similar dosages (300–450 mg/day), target blood levels (0.3–0.8 mEq/L), outcome measures, and trial duration (13 months) as the positive trial. However, taking riluzole was not a requirement for study entry. Placebo outcomes in patients matched for baseline features from a large database of recent clinical trials, showing stable rates of decline over the past 9 years, were used as historical controls. Results: The mean rate of decline of the ALS Functional Rating Scale–Revised was greater in 107 patients taking lithium carbonate (−1.20/month, 95% confidence interval [CI] −1.41 to −0.98) than that in 249 control patients (−1.01/month, 95% CI −1.11 to −0.92, p = 0.04). There were no differences in secondary outcome measures (forced vital capacity, time to failure, and quality of life), but there were more adverse events in the treated group. Conclusions: The lack of therapeutic benefit and safety concerns, taken together with similar results from 2 other recent trials, weighs against the use of lithium carbonate in patients with ALS. The absence of drift over time and the availability of a large database of patients for selecting a matched historical control group suggest that use of historical controls may result in more efficient phase II trials for screening putative ALS therapeutic agents. Classification of evidence: This study provided Class IV evidence that lithium carbonate does not slow the rate of decline of function in patients with ALS over 13 months.

Targeting protein homeostasis in sporadic inclusion body myositis

Augmenting the heat shock response with arimoclomol ameliorates pathology in cellular and animal models of inclusion body myositis. Targeting protein dyshomeostasis in myopathy Sporadic inclusion body myositis (sIBM) is a debilitating adult myopathy that is difficult to treat. Although both inflammation and protein dyshomeostasis have been implicated in sIBM pathogenesis, treatments have only targeted the inflammatory component, and all have failed in clinical trials. In a new study, Ahmed et al. tested the effects of targeting protein dyshomeostasis using arimoclomol, a co-inducer of the heat shock response. In rat myoblast cell culture, arimoclomol reduced key pathological features of IBM. In mutant valosin-containing protein (VCP) mice, which develop an inclusion body myopathy, treatment with arimoclomol ameliorated disease pathology and improved muscle function. The authors then treated a small number of sIBM patients with arimoclomol and showed that it was safe and well tolerated. Sporadic inclusion body myositis (sIBM) is the commonest severe myopathy in patients more than 50 years of age. Previous therapeutic trials have targeted the inflammatory features of sIBM but all have failed. Because protein dyshomeostasis may also play a role in sIBM, we tested the effects of targeting this feature of the disease. Using rat myoblast cultures, we found that up-regulation of the heat shock response with arimoclomol reduced key pathological markers of sIBM in vitro. Furthermore, in mutant valosin-containing protein (VCP) mice, which develop an inclusion body myopathy, treatment with arimoclomol ameliorated disease pathology and improved muscle function. We therefore evaluated arimoclomol in an investigator-led, randomized, double-blind, placebo-controlled, proof-of-concept trial in sIBM patients and showed that arimoclomol was safe and well tolerated. Although arimoclomol improved some IBM-like pathology in the mutant VCP mouse, we did not see statistically significant evidence of efficacy in the proof-of-concept patient trial.

Pompe Disease: Literature Review and Case Series

Pompe disease is a rare multi-systemic metabolic myopathy caused by autosomal recessive mutations in the acidic alpha glucosidase (GAA) gene. Significant progress had been made in the diagnosis and management of patients with Pompe disease. Here, we describe our experience with 12 patients with various forms of Pompe disease including 4 potentially pathogenic, novel GAA variants. We also review the recent the recent advances in the pathogenesis, diagnosis, and treatment of individuals with Pompe disease.

Ocular myasthenia gravis in an academic neuro-ophthalmology clinic: clinical features and therapeutic response.

Objective: The frequency of ocular myasthenia gravis (OMG) in patients referred to an academic neuro-ophthalmology clinic for suspected myasthenia gravis is not known. Our objective was to determine the frequency of ocular OMG in patients referred to an academic neuro-ophthalmologist and determine alternate diagnoses and response to therapy. Methods: We performed a retrospective chart review of patients presenting to the University of Kansas Neuro-Ophthalmology Clinic with suspected OMG over 9 years. We defined OMG as isolated ptosis/diplopia at initial presentation supported by at least one of the following abnormal tests: edrophonium test, ice test, Cogan lid twitch, fatigability on sustained upgaze, acetylcholine receptor binding antibody, greater than 10% decrement on repetitive stimulation, or abnormal single-fiber jitter. We also determined the cause of ptosis/diplopia if it was not the result of OMG. Patients who progressed from OMG to generalized disease were termed transformed myasthenia gravis (TMG). Results: One hundred thirty-eight patients were referred with mean age at presentation 58 ± 19 years. Myasthenia gravis was diagnosed in 101 patients; 95 had OMG; six had generalized MG. Diagnosis in the other 37 was cranial nerve palsies (nine), levator dehiscence (five), multiple sclerosis (two), blepharospasm (two), decompensated phorias (three), accommodation spasm (four), exophoria (three), skew deviation (two), Graves disease (one), hypertropia (one), myopathy (one), neurosarcoidosis (one), progressive supranuclear palsy (one), Miller Fisher variant of Guillain-Barre syndrome (one), and obstructive sleep apnea (one). Mean follow-up was 3.0 ± 2.8 years. Test sensitivity/specificity in OMG was fatigability on sustained upgaze 0.80/0.63; ice pack 0.80/0.25; Cogan lid twitch 0.59/1.00; edrophonium 0.88/0.50; acetylcholine receptor binding antibody 0.38/1.00; repetitive nerve stimulation 0.24/1.00; and single-fiber electromyography 0.90/1.00. Pyridostigmine was used without prednisone in 59 of 97 patients with OMG and 12 of 59 developed TMG. Prednisone was used in 38 patients; 21 of 38 (55%) met Myasthenia Gravis Foundation of America improvement status and none had TMG. Conclusion: The diagnosis of myasthenia gravis was confirmed in the majority of patients referred to our academic neuro-ophthalmology clinic, but 27% did not have myasthenia gravis. It is possible that prednisone treatment of OMG may prevent progression to TMG, but further study is required.

Western ALS study group

As a prelude to carrying out ALS clinical trials, our Western ALS (WALS) study group carried out a natural history study of 167 ALS patients using 42 strength and functional efficacy assessments at monthly intervals at 5 centers. The results demonstrated that declining pulmonary function correlated closely with death. The study also highlighted the variability in measurements and the importance of vigorous training and monitoring.

Rare variants in SQSTM1 and VCP genes and risk of sporadic inclusion body myositis

Genetic factors have been suggested to be involved in the pathogenesis of sporadic inclusion body myositis (sIBM). Sequestosome 1 (SQSTM1) and valosin-containing protein (VCP) are 2 key genes associated with several neurodegenerative disorders but have yet to be thoroughly investigated in sIBM. A candidate gene analysis was conducted using whole-exome sequencing data from 181 sIBM patients, and whole-transcriptome expression analysis was performed in patients with genetic variants of interest. We identified 6 rare missense variants in the SQSTM1 and VCP in 7 sIBM patients (4.0%). Two variants, the SQSTM1 p.G194R and the VCP p.R159C, were significantly overrepresented in this sIBM cohort compared with controls. Five of these variants had been previously reported in patients with degenerative diseases. The messenger RNA levels of major histocompatibility complex genes were upregulated, this elevation being more pronounced in SQSTM1 patient group. We report for the first time potentially pathogenic SQSTM1 variants and expand the spectrum of VCP variants in sIBM. These data suggest that defects in neurodegenerative pathways may confer genetic susceptibility to sIBM and reinforce the mechanistic overlap in these neurodegenerative disorders.