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.

Satisfactory Response With Achieving Maintenance Low-Dose Prednisone in Generalized Myasthenia Gravis.

OBJECTIVES: To estimate the satisfactory response rate (SR%) with achieving maintenance, low-dose prednisone in acetylcholine receptor antibody-positive generalized myasthenia gravis. METHODS: In this retrospective study, we estimate the SR% as defined by (remission/minimal manifestations status for at least 6 months using 7.5 mg or less of prednisone daily, for maintenance treatment at 2, 4, and 6 years after symptoms onset) for patients who were not taking steroid-sparing immunosuppressant (SSI) as a primary outcome and for patients taking an SSI as a secondary outcome. RESULTS: Forty-five patients were not taking an SSI at 2 years, 34 patients at 4 years, and 17 patients at 6 years; SR% was 44.4%, 64.7%, and 58.8%, respectively. Thirty-six patients were taking an SSI at 2 years, 22 patients at 4 years, and 15 patients at 6 years; the SR% was 50.0%, 45.4%, and 66.7%, respectively. CONCLUSIONS: Nearly half of the generalized myasthenia gravis patients who were not taking an SSI achieved an SR.

Less is More in Diabetic Neuropathy Diagnosis: Comparison of Quantitative Sudomotor Axon Reflex and Skin Biopsy.

OBJECTIVES: To compare the frequency of abnormalities in epidermal nerve fiber density (ENFD) and quantitative sudomotor axon reflex (QSART) in patients with diabetic distal symmetric polyneuropathy (DSPN). METHODS: Nerve conduction studies, ENFD, and QSART data were obtained pre- and postexercise, in patients enrolled in a prospective diabetic neuropathy study. McNemar's test was applied to compare the yield of ENFD and QSART. RESULTS: Eighteen patients (58 ± 4 years) were enrolled, with 36 data collection points. In diabetic DSPN and diabetic large fiber DSPN (DSPN-L), abnormal ENFD (77% and 100% respectively) is more frequent than abnormal QSART (39% and 35%, respectively) (P value = 0.001 in diabetic DSPN and P value = 0.0002 in diabetic DSPN-L), whereas in diabetic small fiber DSPN (DSPN-S), both tests have similar yields (47%). CONCLUSIONS: ENFD has a high diagnostic yield in diabetic DSPN and DSPN-L. Including QSART data adds little to the sensitivity of EFND in DSPN-S.

Targeting protein homeostasis in sporadic inclusion body myositis.

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.

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.

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.

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 (> or =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.

Myasthenia gravis, thymoma, and intestinal pseudo-obstruction: a case report and review.

We report a 28-year-old man who presented with intestinal pseudo-obstruction as the initial manifestation of thymoma, myasthenia gravis, and dysautonomia. The patient's autoantibody profile was characteristic of this constellation of disorders, being positive for both muscle and ganglionic nicotinic acetylcholine receptor antibodies and striational antibody. Inflammatory cell infiltrates were found in the myenteric plexus of the stomach and small intestine. Review of 12 previously reported cases suggests that patients with both myasthenia gravis and dysautonomia in the context of thymoma respond poorly to therapy.