Epidemiological evidence for a hereditary contribution to myasthenia gravis: a retrospective cohort study of patients from North America

OBJECTIVES

To approximate the rate of familial myasthenia gravis and the coexistence of other autoimmune disorders in the patients and their families.

DESIGN

Retrospective cohort study.

SETTING

Clinics across North America.

PARTICIPANTS

The study included 1032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis.

METHODS

Phenotype information of 1032 patients diagnosed with AChR-positive myasthenia gravis was obtained from clinics at 14 centres across North America between January 2010 and January 2011. A critical review of the epidemiological literature on the familial rate of myasthenia gravis was also performed.

RESULTS

Among 1032 patients, 58 (5.6%) reported a family history of myasthenia gravis. A history of autoimmune diseases was present in 26.6% of patients and in 28.4% of their family members.

DISCUSSION

The familial rate of myasthenia gravis was higher than would be expected for a sporadic disease. Furthermore, a high proportion of patients had a personal or family history of autoimmune disease. Taken together, these findings suggest a genetic contribution to the pathogenesis of myasthenia gravis.

Gut inflammation and dysbiosis in human motor neuron disease

Amyotrophic lateral sclerosis (ALS) is a systemic disorder that involves dysfunction of multiple organs. Growing evidence has shown that neurodegenerative disorders with gut dysbiosis affect the central nervous system via pro-inflammatory mediators thus impacting gut-brain communications. We have demonstrated dysbiosis and increased intestinal permeability in the SOD1^G93A ALS mouse model. In this study, we comprehensively examined the human gut microbiome in stool samples and evaluated infection and markers of intestinal inflammation in five patients with ALS and motor neuron disorders. Five patients we studied all had alteration in their gut microbiome characterized by a low diversity of the microbiome, compared to healthy cohorts with relatively intact abundance. Firmicutes and Bacteroidetes are the two major members of bacteria at the phylum level. Low Ruminococcus spp occurred in three patients with low Firmicutes/Bacteroidetes (F/B) ratio. A majority of patients had signs of intestinal inflammation. This is the first comprehensive examination of inflammatory markers in the stool of ALS patients. Studies in gut health and microbiome related to the onset and progression of ALS may reveal novel therapeutic targets for disease modulation.

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.

GFPT1-myasthenia: clinical, structural, and electrophysiologic heterogeneity

OBJECTIVE

To identify patients with GFPT1-related limb-girdle myasthenia and analyze phenotypic consequences of the mutations.

METHODS

We performed genetic analysis, histochemical, immunoblot, and ultrastructural studies and in vitro electrophysiologic analysis of neuromuscular transmission.

RESULTS

We identified 16 recessive mutations in GFPT1 in 11 patients, of which 12 are novel. Ten patients had slowly progressive limb-girdle weakness responsive to cholinergic agonists with onset between infancy and age 19 years. One patient (no. 6) harbored a nonsense mutation and a second mutation that disrupts the muscle-specific GFPT1 exon. This patient never moved in utero, was apneic and arthrogrypotic at birth, and was bedfast, tube-fed, and barely responded to therapy at age 6 years. Histochemical studies in 9 of 11 patients showed tubular aggregates in 6 and rimmed vacuoles in 3. Microelectrode studies of intercostal muscle endplates in 5 patients indicated reduced synaptic response to acetylcholine in 3 and severely reduced quantal release in patient 6. Endplate acetylcholine receptor content was moderately reduced in only one patient. The synaptic contacts were small and single or grape-like, and quantitative electron microscopy revealed hypoplastic endplate regions. Numerous muscle fibers of patient 6 contained myriad dilated and degenerate vesicular profiles, autophagic vacuoles, and bizarre apoptotic nuclei. Glycoprotein expression in muscle was absent in patient 6 and reduced in 5 others.

CONCLUSIONS

GFPT1-myasthenia is more heterogeneous than previously reported. Different parameters of neuromuscular transmission are variably affected. When disruption of muscle-specific isoform determines the phenotype, this has devastating clinical, pathologic, and biochemical consequences.

Functional defect in regulatory T cells in myasthenia gravis

Forkhead box P3 (FOXP3) is a transcription factor necessary for the function of regulatory T cells (T(reg) cells). T(reg) cells maintain immune homeostasis and self-tolerance and play an important role in the prevention of autoimmune disease. Here, we discuss the role of T(reg) cells in the pathogenesis of myasthenia gravis (MG) and review evidence indicating that a significant defect in T(reg) cell in vitro suppressive function exists in MG patients, without an alteration in circulating frequency. This functional defect is associated with a reduced expression of key functional molecules, such as FOXP3 on isolated T(reg) cells, and appears to be more pronounced in immunosuppression-naive MG patients. In vitro administration of granulocyte macrophage-colony-stimulating factor (GM-CSF) enhanced the suppressive function of T(reg) cells and upregulated FOXP3 expression. These findings indicate a clinically relevant T(reg) cell-intrinsic defect in immune regulation in MG that may reveal a novel therapeutic target.

Granulocyte macrophage colony-stimulating factor treatment of a patient in myasthenic crisis: effects on regulatory T cells

INTRODUCTION

In this study we describe a patient with a prolonged myasthenic crisis refractory to conventional immunomodulatory therapy who was treated with GM-CSF (granulocyte macrophage colony-stimulating factor, sargramostim).

METHODS

T-regulatory cell (Treg) suppressive function and Foxp3 expression were evaluated before and after treatment with GM-CSF.

RESULTS

Treatment with GM-CSF was associated with clinical improvement, expansion in the circulating numbers of Foxp3(+) cells, increase in Foxp3 expression levels in Tregs, early improvement in Treg suppressive capacity for AChR-α-induced T-cell proliferation, and subsequent enhancement in Treg suppression of polyclonal T-cell proliferation.

CONCLUSION

Although definitive conclusions cannot be drawn from a single case, the correlation with similar findings in GM-CSF-treated animals with experimental autoimmune myasthenia gravis suggests further exploration of the effects of GM-CSF in myasthenia gravis should be studied in a clinical trial setting.

Broken heart syndrome in myasthenia gravis

Broken heart syndrome or stress-induced non-ischemic cardiomyopathy (SICM) has rarely been reported in the setting of myasthenic crisis. We describe a case of reversible SICM that occurred simultaneously with myasthenic crisis in a 77-year-old man without prior cardiac history, and we discuss the previous findings that support an association of other cardiac disorders with myasthenia gravis.

Disseminated intravascular large-cell lymphoma with initial presentation mimicking Guillain-Barré syndrome

We report a patient with intravascular large B-cell lymphoma who initially presented with acute ascending weakness and sensory changes. Electrodiagnostic testing and cerebral spinal fluid (CSF) studies were initially suggestive of a demyelinating polyneuropathy. Further clinical evaluation and testing were consistent with mononeuropathy multiplex. Autopsy revealed disseminated intravascular large-cell lymphoma. Intravascular large-cell lymphoma should be considered in the differential diagnosis of a rapidly evolving neuropathy associated with other organ involvement.

Etanercept treatment in myasthenia gravis

Etanercept is a tumor necrosis factor (TNF) blocking agent that has been shown to suppress ongoing experimental autoimmune myasthenia gravis (EAMG). This subcutaneously administered TNF blocking agent has also been shown to be safe and effective in several rheumatological diseases including rheumatoid arthritis, psoriasis, and ankylosing spondylitis. A prospective clinical pilot trial of etanercept in corticosteroid-dependent autoimmune myasthenia gravis (MG) patients supports further study into etanercept as a treatment for MG.

A novel, efficient, randomized selection trial comparing combinations of drug therapy for ALS

Combining agents with different mechanisms of action may be necessary for meaningful results in treating ALS. The combinations of minocycline-creatine and celecoxib-creatine have additive effects in the murine model. New trial designs are needed to efficiently screen the growing number of potential neuroprotective agents. Our objective was to assess two drug combinations in ALS using a novel phase II trial design. We conducted a randomized, double-blind selection trial in sequential pools of 60 patients. Participants received minocycline (100 mg)-creatine (10 g) twice daily or celecoxib (400 mg)-creatine (10 g) twice daily for six months. The primary objective was treatment selection based on which combination best slowed deterioration in the ALS Functional Rating Scale-Revised (ALSFRS-R); the trial could be stopped after one pool if the difference between the two arms was adequately large. At trial conclusion, each arm was compared to a historical control group in a futility analysis. Safety measures were also examined. After the first patient pool, the mean six-month decline in ALSFRS-R was 5.27 (SD=5.54) in the celecoxib-creatine group and 6.47 (SD=9.14) in the minocycline-creatine group. The corresponding decline was 5.82 (SD=6.77) in the historical controls. The difference between the two sample means exceeded the stopping criterion. The null hypothesis of superiority was not rejected in the futility analysis. Skin rash occurred more frequently in the celecoxib-creatine group. In conclusion, the celecoxib-creatine combination was selected as preferable to the minocycline-creatine combination for further evaluation. This phase II design was efficient, leading to treatment selection after just 60 patients, and can be used in other phase II trials to assess different agents.

Mycophenolate mofetil in dermatomyositis: is it safe?

The authors report 10 patients with idiopathic dermatomyositis treated with mycophenolate mofetil in combination with corticosteroids. Successful steroid taper without disease relapse was achieved in six patients; however, in three patients, treatment was associated with opportunistic infections, leading to death in one patient. The disproportionately high rate of opportunistic infections in this group is considered.

Predictive value of serum anti-C1q antibody levels in experimental autoimmune myasthenia gravis

Components of the complement cascade and circulating immune complexes play important roles in both experimental autoimmune myasthenia gravis and myasthenia gravis in humans. Thus far, no serological factor has been identified to predict the clinical severity of either myasthenia gravis. Upon immunization with acetylcholine receptor, levels of complement factors C1q, C3 and CIC increase with time in sera from C57BL/6 (B6) mice. Both these and plasma samples from myasthenia gravis patients also contain anti-C1q antibodies. The serum levels of anti-C1q antibodies but not C1q, C3 and CIC are significantly correlated with the clinical severity in the experimental myasthenia mice. However, this correlation is not observed in myasthenia gravis patients.

Late appearance of dropped head syndrome after radiotherapy for Hodgkin's disease

We present three cases of dropped head syndrome that occurred as a complication of mantle field (i.e., lymph nodes of the neck, axillae, and mediastinum) or whole-body radiation therapy for Hodgkin's disease. These cases are characterized by a late onset (2-27 years after radiation treatment), fibrosis, and contraction of the anterior cervical muscles, and atrophy of the posterior neck and shoulder girdle. This report adds to the increasing literature about the late neurological complications of radiation therapy and describes a previously unrecognized cause of dropped head syndrome.

Copper deficiency myeloneuropathy and pancytopenia secondary to overuse of zinc supplementation

The haematological complications of acquired copper deficiency have been well documented, but the neurological complications have only recently been reported. An illustrative case of copper deficiency myeloneuropathy with pancytopenia is presented and the potential aetiologies and neurological manifestations of this deficiency state discussed.

Myasthenia gravis patients with low plasma IL-6 and IFN-γ benefit from etanercept treatment

Steroid-dependent myasthenia gravis patients improved following treatment with etanercept (recombinant human TNF receptor:Fc) in a prospective pilot trial. While the plasma anti-acetylcholine receptor antibody levels remained unaffected, etanercept treatment increased plasma levels of C3, circulating immune complexes, IL-10 and IFN-gamma. There was a direct correlation between plasma IL-6, TNF-alpha and IFN-gamma levels and the post-treatment clinical scores of patients. Moreover, patients with lower pre-treatment plasma IL-6 and IFN-gamma levels attained better clinical improvement following etanercept treatment.

Etanercept treatment in corticosteroid-dependent myasthenia gravis

The authors report a prospective pilot trial of etanercept in corticosteroid-dependent autoimmune myasthenia gravis. Eleven patients were enrolled, with eight completing the 6-month trial. Two patients were withdrawn owing to disease worsening, and one patient was withdrawn because of an erythematous skin rash. Six of the eight patients who completed the trial improved, based on quantitative measures of muscle strength and lowering of corticosteroid requirement.

Mycophenolate mofetil for myasthenia gravis: an analysis of efficacy, safety, and tolerability

The authors report a retrospective analysis of the use of mycophenolate mofetil (MyM) in 85 patients with autoimmune myasthenia gravis. The Myasthenia Gravis Foundation of America (MGFA) postintervention status (PIS) was used to characterize the treatment response in each patient. Sixty-two patients (73%) achieved a PIS status indicating improvement. Quantitative strength testing performed on the majority of patients before and after treatment also improved. Side effects to MyM were observed in 27% of patients but required discontinuation in only 6%.

Single Fiber EMG as an Outcome Measure in Myasthenia Gravis: Results from a Double-Blind, Placebo-Controlled Trial

In a placebo-controlled, therapeutic, pilot trial of mycophenolate mofetil (MM) in autoimmune myasthenia gravis (MG), the authors compared pretreatment and posttreatment single fiber electromyography (SFEMG) jitter measurements performed on the same muscle in a total of 11 patients. The mean jitter value decreased (improved) by an average of 15.4 micros in patients receiving MM (n = 6), compared to an increase (worsening) in mean jitter of 4.0 micros in patients receiving placebo (n = 5). This difference was statistically significant (P = 0.030). In most patients, the change in SFEMG measurements correlated with the change in clinical state as measured by quantitative testing of muscle function. The authors conclude that immunomodulation by MM improves neuromuscular junction function in MG and that SFEMG may be a useful marker of early response in future therapeutic trials in autoimmune MG.

Mycophenolate Mofetil for Myasthenia Gravis A Double-Blind, Placebo-Controlled Pilot Study

Mycophenolate mofetil (MM) is an immunosuppressive agent developed and originally used to prevent acute rejection of solid-organ transplantation. There have been preliminary reports of its successful use in the treatment of autoimmune myasthenia gravis (MG). We conducted a double-blind, placebo-controlled pilot trial of MM in the treatment of suboptimally controlled, stable MG. Results of this pilot study are promising and suggestive of greater improvement in the patients who received MM compared to placebo.

Fatigue and abnormal neuromuscular transmission in Kennedy's disease

We describe a patient with Kennedy's disease (X-linked bulbospinal neuronopathy) who experienced leg muscle fatigue with long-distance running. The patient also reported muscle twitching involving the face and extremities and long-standing muscle cramps. Aside from mild facial and tongue weakness (and fasciculations), his examination was normal, including completely preserved muscle strength in the extremities. Electrodiagnostic evaluation revealed evidence for a chronic motor axonopathy/neuronopathy and abnormal sensory nerve action potentials. In addition, repetitive nerve stimulation studies were normal, but neuromuscular jitter tested in the same muscle was markedly abnormal. The normal clinical strength and repetitive nerve stimulation studies in a muscle showing markedly increased neuromuscular jitter suggested a mechanism for this patient's symptoms of muscle fatigue, related to failure of neuromuscular transmission at a critical number of endplates during extremes of physical activity.

Monomelic amyotrophy with late progression

Monomelic amyotrophy is a sporadic juvenile-onset disease that presents with gradual onset of weakness and atrophy in the hand muscles unilaterally. Generally, this disease is considered a 'benign' and non-progressive motor neuron disease, which stabilizes within five years of onset. We discuss a case that illustrates that monomelic amyotrophy may rarely exhibit late clinical progression to the lower extremities after a prolonged period of disease stability.

HMG-CoA Reductase Inhibitor Myopathy: Clinical, Electrophysiological, and Pathologic Data in Five Patients

OBJECTIVES

To define the clinical, electrophysiological, and pathologic features of the myopathy associated with the use of HMG CoA reductase inhibitors.

METHODS

Five patients with myopathy associated with HMG CoA reductase inhibitors were evaluated. Complete histories, physical examinations, manual muscle testing, serum creatine kinase, urine myoglobin measurements, electrodiagnostic studies, and muscle biopsy were performed.

RESULTS

Consistent features in our patients included a subacute onset of myalgias and weakness, electromyography demonstrating electrical myotonia, elevated creatine kinase levels, and in some patients myoglobinuria despite a relative lack of muscle necrosis on muscle biopsy and preserved myofibrillatory architecture by electron microscopy. All patients experienced resolution of symptoms within 3 weeks of drug discontinuation.

CONCLUSIONS

We postulate that the constellation of clinical, electrophysiological, and pathologic findings among our patients with HMG CoA reductase inhibitor myopathy may be explained by the early toxic effects of HMG CoA reductase inhibitors on muscle membrane organelles and sarcolemmal function. Patients on concurrent therapy with cyclosporine, gemfibrozil, and antifungal agents of the azole groups are at an increased risk of developing this toxic myopathy.

Treatment of myasthenia gravis with mycophenolate mofetil: a case report

We report a patient with myasthenia gravis (MG) who had marked clinical benefit in response to treatment with mycophenolate mofetil as documented by serial quantitative measures of strength and muscle fatigue. Our patient had experienced either adverse side effects or a suboptimal response to the usual immunosuppressive agents used in MG. Mycophenolate mofetil was used in combination with cyclosporine and prednisone and allowed for significant reductions in dosage of these immunosuppressants. We conclude that mycophenolate mofetil deserves further study as a therapeutic agent in MG. In particular, its role as a steroid-sparing agent and as a drug to be used in combination immunotherapy in more severe or refractory cases of MG should be investigated.

Electrodiagnostic significance of supramaximally stimulated A-waves

A-waves are generally considered a nonspecific finding of unclear electrodiagnostic and clinical significance. We systematically identified A-waves during routine F-wave studies and defined them as supramaximally elicited reproducible intermediate to late responses that are clearly separate from the M-responses. In patients with A-waves, we noted electrophysiologic diagnoses, the nerve in which the A-wave was identified, the presence of A-waves in multiple nerves, and A-wave morphology. In 54 of 1,258 studies performed, A-waves were present in one or more nerves. Electrophysiologic diagnoses in patients with A-waves included diffuse axonal neuropathy (11.5%), demyelinating neuropathy (66.7%), motor neuron disease (6.5%), radiculopathy (3.6%), mononeuropathy (3.9%), and normal (tibial nerve only) 0.7%. A-waves were abnormal when found in any nerve except the tibial nerve. They were particularly prevalent and present in multiple nerves in acquired and hereditary demyelinating neuropathies, and they more often had a complex morphology. We postulate that demyelination is the crucial underlying pathophysiologic correlate of the supramaximally stimulated A-wave.

Chronic inflammatory demyelinating polyneuropathy after treatment with interferon-alpha

Treatment with interferon-alpha (IFN-alpha) has been associated with the occurrence of a number of autoimmune disorders. We report a case of chronic inflammatory demyelinating polyneuropathy (CIDP) occurring in a patient with a chronic viral hepatitis C infection who received a novel, long-acting form of IFN-alpha. After withdrawal of the interferon treatment, this patient responded to a single extended course of plasma exchange that resulted in a complete clinical remission of symptoms without relapse.

Distinguishing clinical and electrodiagnostic features of X-linked bulbospinal neuronopathy

X-linked bulbospinal neuronopathy (XLBSN) or Kennedys disease is a rare inherited neuromuscular disease characterized by adult-onset muscle weakness, usually in a limb-girdle distribution. It is frequently misdiagnosed despite a distinctive clinical presentation, usually due to the absence of a clear family history, and perhaps also due to failure of recognition. Accurate diagnosis is crucial for genetic counseling purposes and because alternative diagnoses usually carry a poorer prognosis. We evaluated 4 patients with XLBSN and one symptomatic female heterozygote patient. Based on our clinical observations in these patients and a systematic review of previously reported cases, the following clinical and electrophysiologic features when present in the setting of adult-onset muscle weakness, are strongly suggestive of the disorder: 1) facial weakness, 2) facial twitching or fasciculations, 3) tongue weakness and atrophy, 4) postural hand tremor, 5) hypo- or areflexia, and 6) absent or low-amplitude sensory nerve action potentials despite clinically normal sensation. We also hypothesize regarding the possibility of partial expression of the abnormal XLBSN gene in a symptomatic heterozygote female patient.

Complex repetitive discharges: cause or effect of neurogenic muscle hypertrophy?

We report a patient with adult-onset spinal muscular atrophy (SMA) of the scapulohumeral type with neurogenic muscle hypertrophy (NMH) in markedly weakened biceps muscles in association with continuous complex repetitive discharges (CRDs). This is an apparently unique case due to the bilaterality of the NMH associated with CRDs as well as the well-circumscribed symmetric upper extremity distribution of the hypertrophy. The possible mechanisms of NMH in association with spontaneous motor activity are discussed.

Prominent inflammatory changes on muscle biopsy in patients with Miyoshi myopathy

Miyoshi myopathy is a rare autosomal recessive distal myopathy characterized by early and prominent involvement of the posterior compartment of the legs. We describe two patients with the clinical diagnosis of Miyoshi myopathy who demonstrated marked inflammatory changes on muscle biopsy of clinically less affected muscles. This report illustrates the importance of recognizing the marked variability in histopathology of Miyoshi myopathy which may include an inflammatory infiltrate on muscle biopsy which mimics the histopathologic picture of an inflammatory myopathy.