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ObjectiveTo evaluate whether eculizumab helps patients with anti–acetylcholine receptor–positive (AChR+) refractory generalized myasthenia gravis (gMG) achieve the Myasthenia Gravis Foundation of America (MGFA) post-intervention status of minimal manifestations (MM), we assessed patients' status throughout REGAIN (Safety and Efficacy of Eculizumab in AChR+ Refractory Generalized Myasthenia Gravis) and its open-label extension.MethodsPatients who completed the REGAIN randomized controlled trial and continued into the open-label extension were included in this tertiary endpoint analysis. Patients were assessed for the MGFA post-intervention status of improved, unchanged, worse, MM, and pharmacologic remission at defined time points during REGAIN and through week 130 of the open-label study.ResultsA total of 117 patients completed REGAIN and continued into the open-label study (eculizumab/eculizumab: 56; placebo/eculizumab: 61). At week 26 of REGAIN, more eculizumab-treated patients than placebo-treated patients achieved a status of improved (60.7% vs 41.7%) or MM (25.0% vs 13.3%; common OR: 2.3; 95% CI: 1.1–4.5). After 130 weeks of eculizumab treatment, 88.0% of patients achieved improved status and 57.3% of patients achieved MM status. The safety profile of eculizumab was consistent with its known profile and no new safety signals were detected.ConclusionEculizumab led to rapid and sustained achievement of MM in patients with AChR+ refractory gMG. These findings support the use of eculizumab in this previously difficult-to-treat patient population.ClinicalTrials.gov IdentifierREGAIN, NCT01997229; REGAIN open-label extension, NCT02301624.Classification of EvidenceThis study provides Class II evidence that, after 26 weeks of eculizumab treatment, 25.0% of adults with AChR+ refractory gMG achieved MM, compared with 13.3% who received placebo.

Background and ObjectivesWe aimed to determine the genetic and clinical phenotypes of patients with desmin-related myopathy and long-term outcomes after cardiac transplantation.MethodsWe performed a retrospective review of cardiac and neurologic manifestations of patients with genetically confirmed desmin-related myopathy (January 1, 1999–January 1, 2020).ResultsTwenty-five patients in 20 different families were recognized. Median age at onset of symptoms was 20 (range 4–50) years; median follow-up time was 36 (range 1–156) months. Twelve patients initially presented with skeletal muscle involvement, and 13 presented with cardiac disease. Sixteen patients had both cardiac and skeletal muscle involvement. Clinically muscle weakness distribution was distal (n = 11), proximal (n = 4), or both (n = 7) in 22 patients. Skeletal muscle biopsy from patients with missense and splice site variants (n = 12) showed abnormal fibers containing amorphous material in Gomori trichrome–stained sections. Patients with cardiac involvement had atrioventricular conduction abnormalities or cardiomyopathy. The most common ECG abnormality was complete atrioventricular block in 11 patients, all of whom required a permanent pacemaker at a median age of 25 (range 16–48) years. Sudden cardiac death resulting in implantable cardioverter-defibrillator (ICD) shocks or resuscitation was reported in 3 patients; a total of 5 patients had ICDs. Orthotopic cardiac transplantation was performed in 3 patients at 20, 35, and 39 years of age.DiscussionPathogenic variants in desmin can lead to varied neurologic and cardiac phenotypes beginning at a young age. Two-thirds of the patients have both neurologic and cardiac symptoms, usually starting in the third decade. Heart transplantation was tolerated with improved cardiac function and quality of life.

ObjectiveTo investigate the diagnostic challenges of congenital myasthenic syndromes (CMS) in adult neuromuscular practice.MethodsWe searched the Mayo Clinic database for patients with CMS diagnosed in adulthood in the neuromuscular clinic between 2000 and 2016. Clinical, laboratory, and electrodiagnostic data were reviewed.ResultsWe identified 34 patients with CMS, 30 of whom had a molecular diagnosis (14 DOK7, 6 RAPSN, 2 LRP4, 2 COLQ, 2 slow-channel syndrome, 1 primary acetylcholine receptor deficiency, 1 AGRN, 1 GFPT1, and 1 SCN4A). Ophthalmoparesis was often mild and present in 13 patients. Predominant limb-girdle weakness occurred in 19 patients. Two patients had only ptosis. Age at onset ranged from birth to 39 years (median 5 years). The median time from onset to diagnosis was 26 years (range 4–56 years). Thirteen patients had affected family members. Fatigable weakness was present when examined. Creatine kinase was elevated in 4 of 23 patients (range 1.2–4.2 times the upper limit of normal). Repetitive nerve stimulation revealed a decrement in 30 patients. Thirty-two patients were previously misdiagnosed with seronegative myasthenia gravis (n = 16), muscle diseases (n = 15), weakness of undetermined cause (n = 8), and others (n = 4). Fifteen patients received immunotherapy or thymectomy without benefits. Fourteen of the 25 patients receiving pyridostigmine did not improve or worsen.ConclusionMisdiagnosis occurred in 94% of the adult patients with CMS and causes a median diagnostic delay of nearly 3 decades from symptom onset. Seronegative myasthenia gravis and muscle diseases were the 2 most common misdiagnoses, which led to treatment delay and unnecessary exposure to immunotherapy, thymectomy, or muscle biopsy.

Objective: To identify and characterize the molecular basis of a syndrome associated with myasthenia, cortical hyperexcitability, cerebellar ataxia, and intellectual disability. Methods: We performed in vitro microelectrode studies of neuromuscular transmission, performed exome and Sanger sequencing, and analyzed functional consequences of the identified mutation in expression studies. Results: Neuromuscular transmission at patient endplates was compromised by reduced evoked quantal release. Exome sequencing identified a dominant de novo variant, p.Ile67Asn, in SNAP25B, a SNARE protein essential for exocytosis of synaptic vesicles from nerve terminals and of dense-core vesicles from endocrine cells. Ca 2+ -triggered exocytosis is initiated when synaptobrevin attached to synaptic vesicles (v-SNARE) assembles with SNAP25B and syntaxin anchored in the presynaptic membrane (t-SNAREs) into an α-helical coiled-coil held together by hydrophobic interactions. Pathogenicity of the Ile67Asn mutation was confirmed by 2 measures. First, the Ca 2+ triggered fusion of liposomes incorporating v-SNARE with liposomes containing t-SNAREs was hindered when t-SNAREs harbored the mutant SNAP25B moiety. Second, depolarization of bovine chromaffin cells transfected with mutant SNAP25B or with mutant plus wild-type SNAP25B markedly reduced depolarization-evoked exocytosis compared with wild-type transfected cells. Conclusion: Ile67Asn variant in SNAP25B is pathogenic because it inhibits synaptic vesicle exocytosis. We attribute the deleterious effects of the mutation to disruption of the hydrophobic α-helical coiled-coil structure of the SNARE complex by replacement of a highly hydrophobic isoleucine by a strongly hydrophilic asparagine.

OBJECTIVE: To investigate the genetic and physiologic basis of the neuromuscular symptoms of hypotonia-cystinuria syndrome (HCS) and isolated PREPL deficiency, and their response to therapy. METHODS: We performed molecular genetic, histochemical, immunoblot, and ultrastructural studies, investigated neuromuscular transmission in vitro in a patient with isolated PREPL deficiency, and evaluated the effect of pyridostigmine in this patient and in 3 patients with the HCS. RESULTS: HCS is caused by recessive deletions involving the SLC3A1 and PREPL genes. The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems. The proband with isolated PREPL deficiency had myasthenic symptoms since birth and a positive edrophonium test but no cystinuria. She and 1 of 3 patients with HCS responded transiently to pyridostigmine during infancy. The proband harbors a paternally inherited nonsense mutation in PREPL and a maternally inherited deletion involving both PREPL and SLC3A1; therefore, the PREPL deficiency determines the phenotype. We detected no PREPL expression in the patient's muscle and endplates. Electrophysiology studies revealed decreased quantal content of the endplate potential and reduced amplitude of the miniature endplate potential without endplate acetylcholine receptor deficiency or altered endplate geometry. CONCLUSION: Isolated PREPL deficiency is a novel monogenic disorder that causes a congenital myasthenic syndrome with pre- and postsynaptic features and growth hormone deficiency. The myasthenic symptoms in PREPL deficiency with or without cystinuria may respond to pyridostigmine in early life. We attribute the myasthenia to abrogated interaction of PREPL with adaptor protein 1. ispartof: NEUROLOGY vol:82 issue:14 pages:1254-1260 ispartof: location:United States status: published

Background: Plectin crosslinks intermediate filaments to their targets in different tissues. Defects in plectin cause epidermolysis bullosa simplex (EBS), muscular dystrophy (MD), and sometimes pyloric atresia. Association of EBS with a myasthenic syndrome (MyS) was documented in a single patient in 1999. Objectives: To analyze the clinical, structural, and genetic aspects of a second and fatal case of EBS associated with a MyS and search for the genetic basis of the disease in a previously reported patient with EBS-MD-MyS. Methods: Clinical observations; histochemical, immunocytochemical, and electron microscopy studies of skeletal muscle and neuromuscular junction; and mutation analysis. Results: An African American man had EBS since early infancy, and progressive muscle weakness, hyperCKemia, and myasthenic symptoms refractory to therapy since age 3 years. Eventually he became motionless and died at age 42 years. At age 15 years, he had a marked EMG decrement, and a reduced miniature endplate potential amplitude. The myopathy was associated with dislocated muscle fiber organelles, structurally abnormal nuclei, focal plasmalemmal defects, and focal calcium ingress into muscle fibers. The neuromuscular junctions showed destruction of the junctional folds, and remodeling. Mutation analysis demonstrated a known p.Arg2319X and a novel c.12043dupG mutation in PLEC1 . The EBS-MD-MyS patient reported in 1999 also carried c.12043dupG and a novel p.Gln2057X mutation. The novel mutations were absent in 200 Caucasian and 100 African American subjects. Conclusions: The MyS in plectinopathy is attributed to destruction of the junctional folds and the myopathy to defective anchoring of muscle fiber organelles and defects in sarcolemmal integrity.

A 9-year-old previously healthy Filipino-American boy presented to a peripheral hospital with a 2-day history of sudden-onset right arm weakness in the setting of intermittent fevers for 1 week prior to presentation. Over the 2 days prior to presentation, he lost the ability to write, grab any objects, or make a fist with his right hand, as well as the ability to lift his right arm to dress himself. Motor examination of the right arm revealed low tone, 0/5 strength for wrist extension, elbow flexion, and elbow extension, and minimal movement of all right hand interossei and lumbricals. Right trapezius strength was 5/5. Lower extremity strength was 5/5 bilaterally. Sensation to light touch, pinprick, position sense, and vibration was intact in the affected limb. Cranial nerves 2 through 12 were grossly intact. Deep tendon reflexes were absent in the right upper extremity and normal on the left. He denied arm pain, change in sensation, recent trauma, and bladder or bowel dysfunction. The pediatric neurology team was consulted and he was admitted to the pediatric ward at the peripheral hospital for further evaluation.

Neurology ® received 1,915 new and 567 revised manuscripts (including about 44 new and 13 revised full-length articles each week) from October 1, 2008, through March 31, 2009. A total of 3,524 reviews were received during this period. Reviews are arriving in an average of 8–9 days. The average time from submission to first decision for papers chosen for review was 30 days during this period compared to 31 days in this same time period during 2008 and 37 days in this same period during 2006–7. Due to page limitations, we have been able to accept about only 20% of full-length papers and 17% of Clinical/Scientific Notes for publication. We appreciate your making specific comments regarding the uniqueness of study populations, novel methods, studies that are especially educational, or new strategies for diagnosing and treating neurologic disease. These specific comments in your reviews greatly assist us in making our decisions. Neurology and the Editors are grateful for your dedication to the journal, which helps us fulfill our goal of publishing the articles that will most benefit authors and readers of Neurology and improve patient care. In appreciation of your time and efforts, we grant an hour of CME credit, if requested, for each manuscript you review for the journal (maximum of 15 credits per year as determined by ACCME). The following criteria will determine whether credit will be granted: “it should be evident that the reviewer has read and understood the content of the manuscript, accompanying figures and tables, supplementary material to be published on the Web site, and references. To receive credit, the reviewer must make comments to the editor that aid him/her in making an informed decision regarding publication of the manuscript and make substantive suggestions to the author.” Credit is not granted for re-reviews unless the review …

Objective: To correlate muscle biopsy findings with prebiopsy and postbiopsy clinical course and response to therapy in polymyositis (PM) and sporadic inclusion body myositis (IBM). Background: Existence of pure PM has recently been questioned; subsequently, the definition and criteria for diagnosing PM were debated. Methods: Patient records, follow-up information, and muscle biopsies were analyzed in 107 patients whose biopsies were initially read as PM and IBM. Results: The patients fell into three groups by combined biopsy and clinical criteria: PM, 27 patients; IBM, 64 patients; PM/IBM, 16 patients with biopsy diagnosis of PM but clinical features of IBM. For the three groups, the respective mean periods from disease onset to end of follow-up were 5.9, 8.5, and 9.6 years. Another autoimmune disease was present in 4 of 27 PM, 8 of 64 IBM, and 1 of 16 PM/IBM cases. An autoimmune serologic marker occurred in one-third of each group. Nineteen PM patients had no associated autoimmune disease or marker. Nonnecrotic fiber invasion by mononuclear cells appeared in all IBM, 17 of 27 PM, and 13 of 16 PM/IBM patients. The density of both invaded fibers and cytochrome- c oxidase–negative fibers was higher in IBM and PM/IBM than in PM. Immunotherapy improved 22 of 27 PM patients but had only transient beneficial effects in 2 of 32 IBM and 1 of 14 PM/IBM patients. Conclusions: 1) Sixteen of 43 patients (37%) with biopsy features of polymyositis (PM) had clinical features of inclusion body myositis (IBM). 2) Absence of canonical biopsy features of IBM from clinically affected muscles of IBM patients challenges biopsy criteria for IBM, or the IBM markers appear late in some patients, or their distribution in muscle is patchy and restricted compared with that of the inflammatory exudate. 3) The muscle biopsy is a reliable instrument in the diagnosis of PM and IBM in close to 85% of the patients. Errors of diagnosis in the remaining 15% can be avoided or reduced by combined evaluation of the clinical and pathologic findings.

The diagnostic aspects of sporadic inclusion-body myositis (s-IBM), and a few comments on our own approach to its treatment, are presented to foster the goals of this symposium, which was organized to provoke new ideas concerning the cause and treatment of this currently unsolvable disease. s-IBM is the most common, progressive, debilitating muscle disease beginning in persons over age 50 years, and it is more common in men. Diagnostic parameters reviewed are clinical, muscle-biopsy histochemistry, electrophysiologic and CSF evaluations. Overall, the degenerative phenomena in s-IBM muscle fibers seem to be the major cause of the progressive, unstoppable weakness, rather than the lymphocytic inflammation. Available treatments are of only slight, temporary benefit for only some s-IBM patients, indicating a desperate need for definitive therapies.

Objective: To review the clinicopathologic features and outcome of sporadic late onset nemaline myopathy (SLONM). Background: Non-HIV–related SLONM is an uncommon disease of undefined etiology. Methods: This study is based on clinical, EMG, histochemical, immunocytochemical, and electron microscopy evaluation, and long-term follow-up of 14 patients observed at the Mayo Clinic between 1975 and 2003. Results: The disease presented between 43 and 81 years and evolved subacutely. The weakness was predominantly proximal in 11, equal proximally and distally in 3, and asymmetric in 4; dysphagia was a symptom in 6. The EMG showed myopathic features with fibrillations but the serum CK level at the time of initial examination or reevaluation was normal or below the Mayo Clinic’s range of normal values for sex and age at the time of the assay. Seven patients had an associated monoclonal gammopathy. On light microscopy, the nemaline structures were best identified in 3-μm-thick frozen sections stained trichromatically or immunostained for α-actinin or myotilin. Electron microscopy done in 12 cases identified the rods in all and revealed additional structural abnormalities. Seven patients with monoclonal gammopathy were followed for 1 to 5 years; five died of respiratory failure. Five patients without monoclonal gammopathy were followed for 4 to 23 years and none died of the disease. Immunotherapy in eight patients was of uncertain benefit. Conclusions: 1) Subacutely evolving weakness after age 40, normal to low CK level, myopathic EMG with fibrillations, and often a monoclonal gammopathy are clues for the diagnosis of sporadic late onset nemaline myopathy. 2) The diagnosis is confirmed by visualizing the rods in trichrome or immunostained cryosections. 3) An associated monoclonal gammopathy heralds an unfavorable prognosis.

Objective: To investigate the morphologic, electrophysiologic, and molecular correlates of muscle-specific tyrosine kinase-seropositive [MuSK(+)] myasthenia gravis (MG). Background: Anti-MuSK antibodies are detected in some of acetylcholine receptor-seronegative [AChR(−)] patients with MG with prominent facial, bulbar, and respiratory muscle involvement. The morphologic and electrophysiologic correlates of MuSK(+) MG have not been investigated to date. Methods: Immunohistochemistry, electron microscopy, and in vitro electrophysiology studies were performed on an intercostal muscle specimen of a patient with MuSK(+) MG and in control subjects. MUSK was directly sequenced, and the nucleotide changes were traced with allele-specific PCR in control subjects. Results: A man aged 34 years has had facial weakness since childhood and progressive bulbar and respiratory muscle weakness and intermittent diplopia since age 21 years. He has thin temporalis and masseter muscles, a high-arched palate, and an atrophic tongue. EMG shows a 36% decrement in facial muscles. His mother has similar facial features. His endplates (EPs) show no AChR or MuSK deficiency, but the amplitudes of the miniature EP potentials and currents are reduced to 35% and 55% of normal, respectively. EP ultrastructure is well preserved, but some junctional folds immunostain faintly for immunoglobulin G. Mutation analysis of MUSK reveals one rare and two common DNA polymorphisms. Conclusions: 1) The circulating anti-muscle-specific tyrosine kinase antibodies caused neither muscle-specific tyrosine kinase nor acetylcholine receptor deficiency at the endplates; 2) the reduced intercostal miniature endplate potential and current amplitudes were not accounted for by acetylcholine receptor deficiency; 3) the faint immunoglobulin G deposits at the endplates may or may not represent anti-muscle-specific tyrosine kinase antibodies; and 4) the anti-muscle-specific tyrosine kinase antibodies may not be the primary cause of myasthenic symptoms in this patient.

Background and Objective: The term myofibrillar myopathy (MFM) is a noncommittal term for a pathologic pattern of myofibrillar dissolution associated with accumulation of myofibrillar degradation products and ectopic expression of multiple proteins. Ultrastructural studies implicate the Z-disk as the site of the initial pathologic change, and mutations in two Z-disk-related proteins, desmin and αB-crystallin, have been identified in a minority of patients with MFM. The authors’ objective was to determine whether mutations in myotilin, a key Z-disk component and the disease protein in limb-girdle muscular dystrophy (LGMD) 1A, are another cause of MFM.Methods: The authors used histochemical, immunocytochemical, ultrastructural, and mutation analysis.Results: The authors detected four missense mutations in 6 of 57 patients with MFM in the serine-rich exon 2 of MYOT, where the two previously identified LGMD1A mutations are located. Three mutations were novel, and one had been previously identified in LGMD1A. Each patient had evidence for neuropathy, and at least three kinships had associated cardiomyopathy. Distal weakness greater than proximal weakness was present in three patients. Except for minor differences, the morphologic features were similar to those in other patients with MFM.Conclusions: 1) Mutations in myotilin cause MFM; 2) exon 2 of MYOT is a hotspot for mutations; 3) peripheral neuropathy, cardiomyopathy, and distal weakness greater than proximal weakness are part of the spectrum of myotilinopathy; 4) not all cases of myotilinopathy have a limb-girdle phenotype; and 5) the molecular basis of the majority of MFM cases remains to be discovered.