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Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients With Positive Acetylcholine Receptor Antibody
Journal Pre-proof Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients with Positive Acetylcholine Receptor Antibody Supanut Apinyawasisuk, Yuda Chongpison, Chawin Thitisaksakul, Supharat Jariyakosol PII:
S0002-9394(19)30477-5
DOI:
https://doi.org/10.1016/j.ajo.2019.09.019
Reference:
AJOPHT 11088
To appear in:
American Journal of Ophthalmology
Received Date: 5 June 2019 Revised Date:
18 September 2019
Accepted Date: 18 September 2019
Please cite this article as: Apinyawasisuk S, Chongpison Y, Thitisaksakul C, Jariyakosol S, Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients with Positive Acetylcholine Receptor Antibody, American Journal of Ophthalmology (2019), doi: https://doi.org/10.1016/j.ajo.2019.09.019. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Inc. All rights reserved.
Abstract Purpose: To evaluate associated factors of conversion of ocular myasthenia gravis (OMG) to generalized myasthenia gravis (GMG) among patients with seropositive acetylcholine receptor antibody (AchR Ab). Design: Retrospective cohort study Methods Setting: Retrospective chart review Patient: Seventy-one OMG patients with seropositive AchR Ab presented during July 2009 and December 2016. The exclusion criteria were 1) patients who first presented with GMG, 2) unable to identify the time of onset of OMG or GMG 3) unable to provide the information about previous treatments prior to the onset of GMG, and 4) incomplete or lost medical records. Observation Procedure: We collected demographic, clinical characteristics including onset of OMG and GMG, presence of other autoimmune disorders, history of smoking, presence of thymic abnormalities, and medications received. Main Outcome Measures: Conversion to GMG and time to conversion.
Results: Thirty-six patients experienced conversion to GMG. Overall incidence of GMG was 14 (95%CI, 10.09-19.4) per 100 patient years. Probability of conversion at 2 years was 0.37 (95%CI, 0.27-0.49). Overall median conversion time was 4.97 year. Cox proportional hazard model showed that risk factors were female sex (HR=2.52, 95%CI: 1.04-6.10), history of smoking (HR; 3.42; 95% CI, 1.40-8.45), and thymic abnormalities (HR; 1.82; 95% CI, 0.91-3.67). Protective factors against conversion to GMG were receiving immuosuppressive agents (HR; 0.42; 95% CI, 0.19-0.97) and pyridostigmine (HR; 0.37; 95% CI, 0.14-0.93). Conclusions: OMG patients with seropositive AchR Ab should be informed that taking pyridostigmine and/or immunosuppressive agents as well as smoking cessation might prevent conversion to GMG.
1 Title page Title: Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients with Positive Acetylcholine Receptor Antibody. Short title: Factors affecting generalization of ocular myasthenia gravis Authors: 1,2 Supanut Apinyawasisuk 3 Yuda Chongpison 4 Chawin Thitisaksakul 1,2 Supharat Jariyakosol Author’s affiliations: 1 Ophthalmology Department, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand 2 Department of Ophthalmology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand 3 Biostatistic Excellence Center, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand 4 Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand Corresponding author: Supanut Apinyawasisuk, MD Address: Ophthalmology Department, King Chulalongkorn Memorial Hospital. 1873 Rama 4 Road, Pathumwan, Bangkok, Thailand 10330 Tel: 662-256-4142 Fax: 662-252-8290 E-mail: [email protected]
Chawin Thitisaksakul conducted the study when he was a medical student at the Faculty of Medicine, Chulalongkorn University. After graduation, he currently works at Trakanphuetphon Hospital, Ubon Ratchathani, Thailand
2 Introduction Ocular myasthenia gravis (OMG) is an autoimmune disorder characterized by fatigable weakness of extraocular muscles, levator palpebrae, and orbicularis oculi resulting in fatigable ptosis and binocular diplopia.1 Approximately 3080% of patients with OMG experience a conversion to generalized myasthenia gravis (GMG) within 2 years.2 These patients not only suffer from ptosis and diplopia but also from limb weakness, bulbar symptoms, or even respiratory failure. Previous studies reported that risk factors of conversion included being female, having older age of onset of OMG, seropositivity to acetylcholine receptor antibody (AchR Ab),3, 4 higher levels of seropositivity to AchR Ab, presence of autoimmune disorders, thymic hyperplasia,2 thymoma,3 and single ocular symptom (having either isolated ptosis or diplopia).5 Protective factor included longer duration of remaining OMG.6 However, previous studies included patients using diagnostic tests with low accuracy for OMG, resulting in possible contamination of studied population by subjects with false positive test. There has been a study reporting that prevalence of current smoking was higher in myasthenia patients compared with general population.7 Moreover, current and former cigarette smoking was associated with both ocular and generalized symptoms severity.8 To our knowledge, no studies investigate whether smoking is associated with an increased risk of conversion to GMG. The purpose of this study is to evaluate the risk and protective factors of having a conversion to GMG, determine time to conversion, and assess factors influencing the time to conversion in patients with AchR Ab seropositive OMG. We hypothesized that patient’s characteristics and healthrelated behavior, OMG initial clinical presentation, and medications received might affect the conversion. Methods This is a retrospective cohort study of patients with OMG who had positive AchR Ab. We extracted the list of patients from the database of Neuroscience Laboratory, Thai Red Cross Emerging Infectious Disease Health Science Center, King Chulalongkorn Memorial Hospital. We retrospectively reviewed charts of all patients who were 18 years old or older and had positive AchR Ab test during July 2009 and December 2016. The exclusion criteria were 1) patients who first presented with GMG, 2) unable to identify the time of onset of OMG or GMG 3) unable to provide the information about previous treatments prior to the onset of GMG, and 4) incomplete or lost medical records. The study protocol was approved by the Faculty of Medicine, Chulalongkorn University’s institutional review board (certificate of approval number 936/2017). The informed consent process was waived for this study. We reviewed a diagnosis of OMG, which was made by experienced neuroophthalmologists or neurologists at our institute based on the presence of fluctuating ptosis and/or diplopia and positive AchR Ab test. The AchR Ab
3 serology test was performed using enzyme-linked immunosorbent assay (ELISA) method. Demographic and clinical characteristics were obtained from medical records. Demographic data included sex and date of birth. Clinical characteristics were onset and status of ocular symptoms (including ptosis and/or diplopia), presence of other autoimmune disorders, history of smoking, medication received prior to conversion to GMG (e.g., pyridostigmine, systemic corticosteroids, and other immunosuppressive agents), date of first treatment (with pyridostigmine and/or immunosuppressive agents), presence of thymic abnormalities (i.e., thymic hyperplasia or thymoma), diagnosis of GMG, and date of onset of GMG. GMG diagnosis was determined by experienced neurologists based on the signs and symptoms of generalization (swallowing difficulty, altered speaking, chewing problem, limited facial expression, proximal muscle weakness, fatigue, respiratory failure). Statistical Analysis Descriptive statistics, including mean and standard deviation (SD), and percentages, were conducted to describe demographic and clinical characteristics. Median and interquartile range (IQR) were used to report the duration of follow up. Student’s t test and chi-squared statistics were used for continuous and categorical variables, respectively. Univariate and multivariable logistic regression models were applied to assess the factors associated with a conversion to GMG. Factors with p-value<0.2 from univariate analysis were included for multivariate logistic regression. Kaplan-Meier curves and log-rank tests were conducted to assess time from OMG diagnosis to conversion to GMG, and compare time to conversion between clinical characteristics, such as history of smoking and having autoimmune disease, respectively. The Cox proportional hazard model evaluated the association of the risk factors and time to GMG conversion. Subjects with lost-to-follow up were considered to be censored. Risk factors, which were evaluated for both logistic regression and Cox proportional hazard model were sex, history of smoking, status of autoimmune disease, use of pyridostigmine or immunosuppressive agents (e.g., systemic corticosteroids or other immunosuppressive agents) prior to GMG conversion, and status of thymic abnormality. Results A total of 184 patients had positive AchR Ab test result during the study period. We excluded 56 patients who first presented with GMG, 18 patients with unknown time of onset of OMG and/or GMG, and 5 patients whose data about previous treatments could not be identified or who had incomplete medical records (Figure 1). Among 105 patients included, 71 patients had complete data of all risk factors and were included in analyses. Among the analysis set (N=71), 35 OMG patients remained no change toward the end of
4 the study (remained OMG group), 36 patients experienced conversion to GMG (GMG group). The median duration of follow up was 4.91 years (IQR: 2.98, 6) in remained OMG group and 0.78 year (IQR: 0.18, 2.47) in GMG group. Three patients in the remained OMG group were lost to follow up. Table 1 summarizes demographic data and characteristics for eligible participants (N=105) and participants with complete data who were included in analyses (N=71). There were 18 (51.4%) female patients in remained OMG group and 25 (69.4%) female patients in GMG group. Mean age of onset of OMG of the whole group was 52.4 years (SD=16 years), whereas means age of OMG onset for the remained OMG group and GMG group were 54.4 years (SD=17.9 years) and 50.5 years (SD=13.8 years), respectively. Associations between demographic and clinical factors and GMG Table 2 shows the odds of conversion to GMG for each risk factor. Females (OR=2.15, 95% CI=0.81-5.67), history of smoking (OR=2.64, 95% CI= 0.818.62), and presence of thymic abnormality (OR= 3.82, 95% CI=1.20-12.18) were associated with a conversion to GMG. Receiving immunosuppressive agents and pyridostigmine prior to conversion to GMG had lower rate of conversion. Crude odds ratio for receiving immunosuppressive agents was 0.29 (95% CI, 0.11-0.78) and 0.16 (95% CI, 0.032-0.78) for pyridostigmine. Age of OMG onset and presence of other autoimmune disorders were not significantly associated with rate of conversion to GMG. The final multivariate logistic regression model included sex, history of smoking, presence of thymic abnormality, use of immunosuppressive agents and use of pyridostigmine. Observed risk factors for conversion to GMG were being female (ORadj=4.02, 95% CI=0.62-18.72), having history of smoking (ORadj = 6.13, 95% CI=1.13-33.23), presence of thymic abnormality (ORadj =4.13, 95% CI=1.09-15.67). Receiving immunosuppressive agents and pyridostigmine were associated with lower rate of conversion. Adjusted odds ratio for receiving immunosuppressive agents was 0.47 (95% CI, 0.14-1.59) and 0.23 (95% CI, 0.04-1.53) for pyridostigmine. Incidence and risk factors for time to conversion Over 258 patient-years (PY) of follow-up, 36 patients developed GMG. Overall incidence of GMG was 14 (95%CI, 10.09-19.4) per 100 PY. The median time of conversion from OMG to GMG in all patients was 4.97 years (Table 4). Female sex, history of smoking, and presence of thymic abnormalities were associated with shorter median conversion time (2.94, 1.85, 1.25 years respectively) while patients who received immunosuppressive agents and pyridostigmine had longer median conversion time (12.49 years for both groups). Moreover, overall probability of conversion from OMG to GMG at 2 years was 0.37. Female sex, history of smoking, and presence of thymic abnormalities were associated with higher probability of conversion while receiving immunosuppressive agents and pyridostigmine were associated with lower probability of conversion at 2, 4, 6 years. Figure 2 shows KaplanMeier curves of each factors.
5 The results of Cox proportional hazard model were in agreement with those of logistic regression models, showing that female sex, history of smoking, and presence of thymic abnormality were associated with a conversion to GMG. Crude hazard ratio was 1.67 (95% CI, 0.82-3.42), 1.88 (95% CI, 0.92-3.86), and 2.19 (95% CI, 1.11-4.32) for female sex, history of smoking, and presence of thymic abnormality (Table 3). Adjusted hazard ratio was 2.52 (95% CI, 1.04-6.10), 3.42 (95% CI, 1.40-8.45), and 1.82 (95% CI, 0.91-3.67) for female sex, history of smoking, and presence of thymic abnormality subsequently. Receiving immunosuppressive agents and pyridostigmine were associated with lower rate of conversion using Cox proportional hazard ratio. Crude hazard ratio was 0.29 (0.15, 0.60) and 0.22 (0.10, 0.46) for immunosuppressive agents and pyridostigmine, respectively. Adjusted hazard ratio was 0.42 (95% CI, 0.19-0.97) and 0.37 (95% CI, 0.14-0.93) for immunosuppressive agents and pyridostigmine, respectively. Discussion In this study, the demographic and clinical factors were evaluated whether they have any relationship with the conversion to GMG among patients with AchR Ab seropositive OMG. Previous studies was in agreement with our study in term of female sex 4 and presence of thymic abnormalities 2, 3, 9, 10 as factors associated with higher rate of conversion to GMG, whereas receiving immunosuppressive agents including systemic corticosteroid was reported as a protective factor and may delay time to the conversion in several studies.3, 9, 11, 12 Table 5 summarizes the results of previous studies investigating conversion of OMG to GMG in different settings. Although most previous studies were performed in both seropositive and seronegative myasthenia patients, Mee et al. 13 investigated the effect of immunotherapy (prednisolone and thymectomy) in their retrospective study of 21 AchR Ab seropositive patients who experienced conversion of OMG to GMG and reported that immunotherapy might prevent conversion in AchR Ab seropositive patients. The population in their study was similar to the population in our study (i.e., only AchR Ab seropositive patients included) and the results from our study was in agreement with their findings in term of receiving immunosuppressive agents as a protective factor. However, there has been no previous study reporting the history of smoking as a risk factor and receiving pyridostigmine as a protective factor of conversion. Our study is the first to show that smoking is a risk factor for a conversion to GMG. Our observed evidence that smoking increased a risk of conversion might be explained by increased autoimmune activities through recruitment of various types of immune cells and inflammatory cytokines induced by smoking as seen in many autoimmune disorder models8 It has been well accepted that smoking increases risk of developing thyroid eye disease (TED) and smokers have higher TED severity. 14 Since TED and myasthenia gravis could coexist, 15 smoking might affect natural history of myasthenia gravis as well. Alternative possible explanation is systemic acetylcholine receptor desensitization caused by long contact of blood nicotine to the whole-body acetylcholine receptor.8, 16 In addition to the previous studies, we emphasize that smoking not only worsens myasthenia gravis activities but also increases the risk of generalization among AchR Ab seropositive patients. Myasthenia
6 patients should be recommended to stop smoking in order to reduce the chance of conversion to GMG and improve both ocular and systemic symptoms. In this study, we found that pyridostigmine use was associated with lower rate of conversion to GMG. Pyridostigmine has been believed to have no effect to the natural history of the disease.1 Its inhibiting effect on acetylcholinesterase results in an increasing level of acetylcholine in the synaptic junction. As a result, pyridostigmine relieves the symptoms of myasthenia gravis. However, pyriostigmine may provide immunomodulatory effect that prevents conversion of OMG to GMG through a cholinergic anti-inflammatory pathway (CAP). Evidence from animal models showed circulating macrophages expressing α7 nicotinic acetylcholine receptor (α7 nAChR) interacts with serum acetylcholine to suppress production of inflammatory cytokines including tumor necrosis factor α, high mobility group boxes of protein (HMGB), and interleukin 6 (IL-6). CAP can be terminated by erythrocyte-bound acetylcholinesterase. Acetylcholinesterase inhibitors, hence, have been proposed to have immunemodulatory effects via CAP activation in addition to their primary action.17 A couple studies reported that HMGB, and IL-6 were involved in immune process in myasthenia gravis.18, 19 Moreover, AchR Ab seropositive patients with GMG had higher serum HMGB level than patients with OMG and control.18 The strength of our study is that we included only definite myasthenia gravis patients diagnosed by positive AchR Ab. The population in our study was not contaminated by subjects diagnosed by other diagnostic modules (e.g. electromyography or responsiveness to acetylcholinesterase inhibitor), which may have more false positive rate. On the other hand, the results from this study might not be able to be generalized to AchR Ab seronegative myasthenia gravis, which is one of our limitations. The other potential limitations included small number of subjects and missing data from old medical records. We are aware that these limitations are the common nature of retrospective study and suggest a larger cohort study with longer follow-up time to investigate the risk and protective factors of conversion to GMG as a future study. Also, it might be interesting to investigate further whether a combination of pyridostigmine and immunosuppressive agents is beneficial. In conclusion, pyridostigmine, currently used as a symptomatic treatment of OMG and immunosuppressive agents showed protective effect to conversion to GMG, and smoking, in addition to presence of thymic abnormalities and female gender may accelerate conversion to GMG. OMG patients should be informed that pyridostigmine or immunosuppressive agents including corticosteroid might be potential treatment option to prevent conversion. Moreover, they should be encouraged to stop smoking in order to reduce the rate of disease progression to GMG, thus saving the patients from extreme burden of muscle weakness, bulbar symptoms, or even life-threatening respiratory failure. Acknowledgements a. Funding/supports: none
7 b. Financial disclosures: All authors have no financial disclosures. c. Other acknowledgements: We would like to thank Abhinbhen Saraya Wasontiwong, MD, MSc for providing data from the database of Neuroscience Laboratory, Thai Red Cross Emerging Infectious Disease Health Science Center, King Chulalongkorn Memorial Hospital.
8 References 1. Vaphiades MS, Bhatti MT, Lesser RL. Ocular myasthenia gravis. Curr Opin Ophthalmol 2012;23(6):537-542. 2. Wong SH, Petrie A, Plant GT. Ocular Myasthenia Gravis: Toward a Risk of Generalization Score and Sample Size Calculation for a Randomized Controlled Trial of Disease Modification. J Neuroophthalmol 2016;36(3):252258. 3. Hong YH, Kwon SB, Kim BJ, et al. Prognosis of ocular myasthenia in Korea: a retrospective multicenter analysis of 202 patients. J Neurol Sci 2008;273(1-2):10-14. 4. Mazzoli M, Ariatti A, Valzania F, et al. Factors affecting outcome in ocular myasthenia gravis. Int J Neurosci 2018;128(1):15-24. 5. Wang L, Zhang Y, He M. Clinical predictors for the prognosis of myasthenia gravis. BMC Neurol 2017;17(1):77. 6. Bever CT, Jr., Aquino AV, Penn AS, Lovelace RE, Rowland LP. Prognosis of ocular myasthenia. Ann Neurol 1983;14(5):516-519. 7. Maniaol AH, Boldingh M, Brunborg C, Harbo HF, Tallaksen CM. Smoking and socio-economic status may affect myasthenia gravis. Eur J Neurol 2013;20(3):453-460. 8. Gratton SM, Herro AM, Feuer WJ, Lam BL. Cigarette Smoking and Activities of Daily Living in Ocular Myasthenia Gravis. J Neuroophthalmol 2016;36(1):37-40. 9. Li F, Hotter B, Swierzy M, Ismail M, Meisel A, Ruckert. Generalization after ocular onset in myasthenia gravis: a case series in Germany. J Neurol 2018;265(12):2773-2782. 10. Teo KY, Tow SL, Haaland B, et al. Low conversion rate of ocular to generalized myasthenia gravis in Singapore. Muscle Nerve 2018;57(5):756760. 11. Kupersmith MJ, Latkany R, Homel P. Development of generalized disease at 2 years in patients with ocular myasthenia gravis. Arch Neurol 2003;60(2):243-248. 12. Sommer N, Sigg B, Melms A, et al. Ocular myasthenia gravis: response to long-term immunosuppressive treatment. J Neurol Neurosurg Psychiatry 1997;62(2):156-162. 13. Mee J, Paine M, Byrne E, King J, Reardon K, O'Day J. Immunotherapy of ocular myasthenia gravis reduces conversion to generalized myasthenia gravis. J Neuroophthalmol 2003;23(4):251-255. 14. Prummel MF, Wiersinga WM. Smoking and risk of graves’ disease. JAMA 1993;269(4):479-482. 15. Bojikian KD, Francis CE. Thyroid eye disease and myasthenia gravis. Int Ophthalmol Clin 2019;59(3):113-124. 16. Moreau T, Vandenabeele S, Depierre P, Confavreux C. Nicotinesensitive myasthenia gravis. Lancet 1995;345(8941):61-62. 17. Pohanka M. Inhibitors of acetylcholinesterase and butyrylcholinesterase meet immunity. Int J Mol Sci 2014;15(6):9809-9825. 18. Uzawa A, Kawaguchi N, Kanai T, Himuro K, Kuwabara S. Serum high mobility group box 1 is upregulated in myasthenia gravis. J Neurol Neurosurg Psychiatry 2015;86(6):695-697. 19. Zhang GX, Navikas V, Link H. Cytokines and the pathogenesis of myasthenia gravis. Muscle Nerve 1997;20(5):543-551.
9 20. Kamarajah SK, Sadalage G, Palmer J, Carley H, Maddison P, Sivaguru A. Ocular presentation of myasthenia gravis: A natural history cohort. Muscle Nerve 2018;57(4):622-627. Figure Legends Figure 1. Study flow chart. Figure legend: AchR Ab, acetylcholine receptor antibody; OMG, ocular myasthenia gravis; GMG, generalized myasthenia gravis Figure 2. Kaplan Meier Curves by demographic and clinical factors associated with conversion to generalized myasthenia gravis
Table 1 Characteristic of patients with and without conversion to generalized myasthenia gravis Total (N=105) Characteristics Age at onset of OMG (mean, SD) Duration of follow up in years (median, IQR)
Remained OMG (N=47) 54.4 (17.6)
GMG (N=58)
Remained OMG (N=35)
GMG (N=36)
50.3 (14.3)
54.4 (17.9)
50.5 (13.8)
4.91 (2.98, 6)
0.78 (0.18, 2.47)
NA N(%)
Complete casesa (n=71)
N(%)
N(%)
N(%)
Sex Female Male History of smoking
28 (59.6%) 19 (40.4%) 6 (14.6%)
42 (72.4%) 16 (27.6%) 13 (33.3%)
18 (51.4%) 17 (48.6%) 5 (14.3%)
25 (69.4%) 11 (30.6%) 11 (30.6%)
Presence of ptosis
45 (95.7%)
57 (98.3%)
33 (94.3%)
36 (50.7%)
Presence of diplopia
29 (61.7%)
44 (75.9%)
24 (68.6%)
28 (77.8%)
Positive RNS
14 (46.7%)
23 (69.7%)
11 (47.8%)
17 (73.9%)
44 (93.6%)
43 (74.1%)
33 (94.3%)
26 (72.2%)b
27 (57.5%)
22 (37.9%)
23 (65.7%)
13 (36.1%)b
6 (15.8%)
23 (42.6%)
5 (14.3%)
14 (38.9%)b
13 (27.7%)
12 (55.2%)
11 (31.4%)
6 (16.7%)
Received pyridostigmine Received immunosuppressive agentsc Presence of thymic abnormalities Presence of other autoimmune disorders
GMG, generalized myasthenia gravis; OMG, ocular myasthenia gravis; RNS , repetitive nerve stimulation test; SD, standard deviation; IQR, interquartile range; NA, not available a number of patients who had complete information of all factors of interest b p<0.05 c including systemic corticosteroid
Table 2 Risk and protective factors for conversion to generalized myasthenia gravis (N = 71) Characteristics Female Diplopia (having Diplopia) Age of onset of ocular myasthenia Smoking status Thymic abnormality Received immunosuppressive agents Received pyridostigmine
Crude Odds Ratio (95%CI) 2.15 (0.81, 5.67) 1.60 (0.55, 4.64) 0.98 (0.96, 1.01)
Adjusteda Odds Ratio (95% CI) 4.02 (0.62, 18.72)b -
2.64 (0.81, 8.62) 3.82 (1.20, 12.18) 0.29 (0.11, 0.78)
6.13 (1.13, 33.23)c 4.13 (1.09, 15.67)c 0.47 (0.14, 1.59)
0.16 (0.032, 0.78)
0.23 (0.04, 1.53)
Reference groups: no smoking, no thymic abnormality, did not receive immunosuppressive agents, did not receive pyridostigmine, no diplopia, being male 95% CI, 95% Confidence Interval Adjusted model includes sex, smoking status, thymic abnormality, received immunosuppressive agents, and received pyridostigmine b p-value = 0.064 c p-value < 0.05 a
Table 3 Hazard ratios of conversion to generalized myasthenia gravis (N = 71) Risk factors
Crude HR (95%CI)
Female Male Smoking Non-smoker Thymic abnormality No thymic abnormality Received immunosuppressive agents Not received Received pyridostigmine Not received
1.67 (0.82, 3.42) 1.0 1.88 (0.92, 3.86) 1.0 2.19 (1.11, 4.32) 1.0 0.29 (0.15, 0.60)
Adjusted HR (95%CI) 2.52 (1.04, 6.10) 1.0 3.42 (1.40, 8.45) 1.0 1.82 (0.91, 3.67) 1.0 0.42 (0.19, 0.97)
1.0 0.22 (0.10, 0.46) 1.0
1.0 0.37 (0.14, 0.93) 1.0
HR, hazard ratio; 95% CI, 95% Confidence Interval
1 Table 4 Median conversion time and probability of conversion by risk factors Median conversion time (years, SE)
Probability of conversion at various years (95% CI) 2 years
4 years
6 years
4.97 (2.33)
0.37 (0.27, 0.49)
0.49 (0.38, 0.62)
0.55 (0.42, 0.68)
Sex Male Female
NA 2.94 (1.63)
0.25 (0.13, 0.45) 0.45 (0.31, 0.60)
0.44 (0.27, 0.66) 0.53 (0.39, 0.69)
0.44 (0.27, 0.66) 0.62 (0.46, 0.78)
Smoking status Yes No
1.85 (0.45) 12.49 (4.90)
0.52 (0.30, 0.78) 0.33 (0.22, 0.47)
0.76 (0.52, 0.94) 0.42 (0.30, 0.56)
0.76 (0.52, 0.94) 0.49 (0.35, 0.65)
1.25 (0.82) NA
0.53 (0.33, 0.76) 0.31 (0.20, 0.46)
0.72 (0.50, 0.91) 0.41 (0.28, 0.56)
0.72 (0.50, 0.91) 0.49 (0.35, 0.66)
0.14 (0.06, 0.30) 0.61 (0.45, 0.77)
0.34 (0.20, 0.53) 0.64 (0.48, 0.80)
0.40 (0.24, 0.61) 0.72 (0.53, 0.88)
0.27 (0.18, 0.41) 0.83 (0.59, 0.97)
0.42 (0.30, 0.57) 0.83 (0.59, 0.97)
0.50 (0.36, 0.66) 0.83 (0.59, 0.97)
Overall
Thymic abnormality Yes No Received immunosuppressive Agents Yes No Received pyridostigmine Yes No
12.49 (0.45) 1.13 (0.63)
12.49 (4.59) 0.08 (0.07)
SE, standard error; 95% CI, 95% Confidence Interval; NA, not available
2
Table 5 Summary of previous studies of risk factors associated with conversion to generalized myasthenia gravis Year
N
Country
1983
108
USA6
1997
78
Germany12
2003
147
USA11
2008
202
Korea3
2016
101
UK2
Diagnostic criteria Conver sion rate 49% • Edrophonium and neostigmine test 31% • AchR Ab • RNS • Clinical signs with: Edrophonium test and treatment response 18.1% • Clinical signs with Edrophonium test 23.3% • Edrophonium test • AchR Ab • RNS • SFEMG 31% • Edrophonium test • Serology test • EMG • Clinical presentation
Median time to conversion <1 year
Risk factors
Protective factors
None
Increased duration of pure OMG
24.5 months
Mild symptoms Normal RNS Low or absent AchR Ab Receiving inmmunosuppressive agents
2 years
AchR Ab seropositive
Prednisone treatment
NA
AchR Ab seropositive Thymoma
Early oral prednisolone treatment
1.31 years
AchR Ab or anti-MuSK seropositive Presence of 1 or more comorbidities
Thymic hyperplasia AchR Ab seropositive Disease onset < 50 years
2017
93
UK20
• Edrophonium test • AchR Ab seropositive • SFEMG • Responsive to ice pack test, pyridostigmine
47.3%
7 months
2017
168
Italy4
• Edrophonium test • AchR Ab, antiMuSK seropositive • SFEMG • RNS • Responsive to pyridostigmine
18.4%
NA
Female sex AchR Ab seropositive
2017
40
China5
• AchR Ab seropositive • SFEMG • RNS • Responsive to pyridostigmine
85%
Mostly < 6 months
Older age of onset
2018
180
Germany9
23.6 months
Thymoma
• AchR Ab seropositive • Anti-MuSK
61.1%
Corticosteroid treatment
seropositive • SFEMG • RNS • Responsive to therapy 10.6% AchR Ab 2018 155 Singapore10 • Edrophonium seropositive test Thymoma • AchR Ab Positive RNS seropositive • SFEMG • RNS • Responsive to pyridostigmine OMG, ocular myasthenia gravis; AchR Ab, acetylcholine receptor antibody; RNS, repetitive nerve stimulation test; SFEMG, singlefiber electromyography; EMG, electromyography; anti-MuSK, anti-muscle specific tyrosine kinase
S0002-9394(19)30477-5
DOI:
https://doi.org/10.1016/j.ajo.2019.09.019
Reference:
AJOPHT 11088
To appear in:
American Journal of Ophthalmology
Received Date: 5 June 2019 Revised Date:
18 September 2019
Accepted Date: 18 September 2019
Please cite this article as: Apinyawasisuk S, Chongpison Y, Thitisaksakul C, Jariyakosol S, Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients with Positive Acetylcholine Receptor Antibody, American Journal of Ophthalmology (2019), doi: https://doi.org/10.1016/j.ajo.2019.09.019. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Inc. All rights reserved.
Abstract Purpose: To evaluate associated factors of conversion of ocular myasthenia gravis (OMG) to generalized myasthenia gravis (GMG) among patients with seropositive acetylcholine receptor antibody (AchR Ab). Design: Retrospective cohort study Methods Setting: Retrospective chart review Patient: Seventy-one OMG patients with seropositive AchR Ab presented during July 2009 and December 2016. The exclusion criteria were 1) patients who first presented with GMG, 2) unable to identify the time of onset of OMG or GMG 3) unable to provide the information about previous treatments prior to the onset of GMG, and 4) incomplete or lost medical records. Observation Procedure: We collected demographic, clinical characteristics including onset of OMG and GMG, presence of other autoimmune disorders, history of smoking, presence of thymic abnormalities, and medications received. Main Outcome Measures: Conversion to GMG and time to conversion.
Results: Thirty-six patients experienced conversion to GMG. Overall incidence of GMG was 14 (95%CI, 10.09-19.4) per 100 patient years. Probability of conversion at 2 years was 0.37 (95%CI, 0.27-0.49). Overall median conversion time was 4.97 year. Cox proportional hazard model showed that risk factors were female sex (HR=2.52, 95%CI: 1.04-6.10), history of smoking (HR; 3.42; 95% CI, 1.40-8.45), and thymic abnormalities (HR; 1.82; 95% CI, 0.91-3.67). Protective factors against conversion to GMG were receiving immuosuppressive agents (HR; 0.42; 95% CI, 0.19-0.97) and pyridostigmine (HR; 0.37; 95% CI, 0.14-0.93). Conclusions: OMG patients with seropositive AchR Ab should be informed that taking pyridostigmine and/or immunosuppressive agents as well as smoking cessation might prevent conversion to GMG.
1 Title page Title: Factors Affecting Generalization of Ocular Myasthenia Gravis in Patients with Positive Acetylcholine Receptor Antibody. Short title: Factors affecting generalization of ocular myasthenia gravis Authors: 1,2 Supanut Apinyawasisuk 3 Yuda Chongpison 4 Chawin Thitisaksakul 1,2 Supharat Jariyakosol Author’s affiliations: 1 Ophthalmology Department, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand 2 Department of Ophthalmology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand 3 Biostatistic Excellence Center, Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand 4 Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand Corresponding author: Supanut Apinyawasisuk, MD Address: Ophthalmology Department, King Chulalongkorn Memorial Hospital. 1873 Rama 4 Road, Pathumwan, Bangkok, Thailand 10330 Tel: 662-256-4142 Fax: 662-252-8290 E-mail: [email protected]
Chawin Thitisaksakul conducted the study when he was a medical student at the Faculty of Medicine, Chulalongkorn University. After graduation, he currently works at Trakanphuetphon Hospital, Ubon Ratchathani, Thailand
2 Introduction Ocular myasthenia gravis (OMG) is an autoimmune disorder characterized by fatigable weakness of extraocular muscles, levator palpebrae, and orbicularis oculi resulting in fatigable ptosis and binocular diplopia.1 Approximately 3080% of patients with OMG experience a conversion to generalized myasthenia gravis (GMG) within 2 years.2 These patients not only suffer from ptosis and diplopia but also from limb weakness, bulbar symptoms, or even respiratory failure. Previous studies reported that risk factors of conversion included being female, having older age of onset of OMG, seropositivity to acetylcholine receptor antibody (AchR Ab),3, 4 higher levels of seropositivity to AchR Ab, presence of autoimmune disorders, thymic hyperplasia,2 thymoma,3 and single ocular symptom (having either isolated ptosis or diplopia).5 Protective factor included longer duration of remaining OMG.6 However, previous studies included patients using diagnostic tests with low accuracy for OMG, resulting in possible contamination of studied population by subjects with false positive test. There has been a study reporting that prevalence of current smoking was higher in myasthenia patients compared with general population.7 Moreover, current and former cigarette smoking was associated with both ocular and generalized symptoms severity.8 To our knowledge, no studies investigate whether smoking is associated with an increased risk of conversion to GMG. The purpose of this study is to evaluate the risk and protective factors of having a conversion to GMG, determine time to conversion, and assess factors influencing the time to conversion in patients with AchR Ab seropositive OMG. We hypothesized that patient’s characteristics and healthrelated behavior, OMG initial clinical presentation, and medications received might affect the conversion. Methods This is a retrospective cohort study of patients with OMG who had positive AchR Ab. We extracted the list of patients from the database of Neuroscience Laboratory, Thai Red Cross Emerging Infectious Disease Health Science Center, King Chulalongkorn Memorial Hospital. We retrospectively reviewed charts of all patients who were 18 years old or older and had positive AchR Ab test during July 2009 and December 2016. The exclusion criteria were 1) patients who first presented with GMG, 2) unable to identify the time of onset of OMG or GMG 3) unable to provide the information about previous treatments prior to the onset of GMG, and 4) incomplete or lost medical records. The study protocol was approved by the Faculty of Medicine, Chulalongkorn University’s institutional review board (certificate of approval number 936/2017). The informed consent process was waived for this study. We reviewed a diagnosis of OMG, which was made by experienced neuroophthalmologists or neurologists at our institute based on the presence of fluctuating ptosis and/or diplopia and positive AchR Ab test. The AchR Ab
3 serology test was performed using enzyme-linked immunosorbent assay (ELISA) method. Demographic and clinical characteristics were obtained from medical records. Demographic data included sex and date of birth. Clinical characteristics were onset and status of ocular symptoms (including ptosis and/or diplopia), presence of other autoimmune disorders, history of smoking, medication received prior to conversion to GMG (e.g., pyridostigmine, systemic corticosteroids, and other immunosuppressive agents), date of first treatment (with pyridostigmine and/or immunosuppressive agents), presence of thymic abnormalities (i.e., thymic hyperplasia or thymoma), diagnosis of GMG, and date of onset of GMG. GMG diagnosis was determined by experienced neurologists based on the signs and symptoms of generalization (swallowing difficulty, altered speaking, chewing problem, limited facial expression, proximal muscle weakness, fatigue, respiratory failure). Statistical Analysis Descriptive statistics, including mean and standard deviation (SD), and percentages, were conducted to describe demographic and clinical characteristics. Median and interquartile range (IQR) were used to report the duration of follow up. Student’s t test and chi-squared statistics were used for continuous and categorical variables, respectively. Univariate and multivariable logistic regression models were applied to assess the factors associated with a conversion to GMG. Factors with p-value<0.2 from univariate analysis were included for multivariate logistic regression. Kaplan-Meier curves and log-rank tests were conducted to assess time from OMG diagnosis to conversion to GMG, and compare time to conversion between clinical characteristics, such as history of smoking and having autoimmune disease, respectively. The Cox proportional hazard model evaluated the association of the risk factors and time to GMG conversion. Subjects with lost-to-follow up were considered to be censored. Risk factors, which were evaluated for both logistic regression and Cox proportional hazard model were sex, history of smoking, status of autoimmune disease, use of pyridostigmine or immunosuppressive agents (e.g., systemic corticosteroids or other immunosuppressive agents) prior to GMG conversion, and status of thymic abnormality. Results A total of 184 patients had positive AchR Ab test result during the study period. We excluded 56 patients who first presented with GMG, 18 patients with unknown time of onset of OMG and/or GMG, and 5 patients whose data about previous treatments could not be identified or who had incomplete medical records (Figure 1). Among 105 patients included, 71 patients had complete data of all risk factors and were included in analyses. Among the analysis set (N=71), 35 OMG patients remained no change toward the end of
4 the study (remained OMG group), 36 patients experienced conversion to GMG (GMG group). The median duration of follow up was 4.91 years (IQR: 2.98, 6) in remained OMG group and 0.78 year (IQR: 0.18, 2.47) in GMG group. Three patients in the remained OMG group were lost to follow up. Table 1 summarizes demographic data and characteristics for eligible participants (N=105) and participants with complete data who were included in analyses (N=71). There were 18 (51.4%) female patients in remained OMG group and 25 (69.4%) female patients in GMG group. Mean age of onset of OMG of the whole group was 52.4 years (SD=16 years), whereas means age of OMG onset for the remained OMG group and GMG group were 54.4 years (SD=17.9 years) and 50.5 years (SD=13.8 years), respectively. Associations between demographic and clinical factors and GMG Table 2 shows the odds of conversion to GMG for each risk factor. Females (OR=2.15, 95% CI=0.81-5.67), history of smoking (OR=2.64, 95% CI= 0.818.62), and presence of thymic abnormality (OR= 3.82, 95% CI=1.20-12.18) were associated with a conversion to GMG. Receiving immunosuppressive agents and pyridostigmine prior to conversion to GMG had lower rate of conversion. Crude odds ratio for receiving immunosuppressive agents was 0.29 (95% CI, 0.11-0.78) and 0.16 (95% CI, 0.032-0.78) for pyridostigmine. Age of OMG onset and presence of other autoimmune disorders were not significantly associated with rate of conversion to GMG. The final multivariate logistic regression model included sex, history of smoking, presence of thymic abnormality, use of immunosuppressive agents and use of pyridostigmine. Observed risk factors for conversion to GMG were being female (ORadj=4.02, 95% CI=0.62-18.72), having history of smoking (ORadj = 6.13, 95% CI=1.13-33.23), presence of thymic abnormality (ORadj =4.13, 95% CI=1.09-15.67). Receiving immunosuppressive agents and pyridostigmine were associated with lower rate of conversion. Adjusted odds ratio for receiving immunosuppressive agents was 0.47 (95% CI, 0.14-1.59) and 0.23 (95% CI, 0.04-1.53) for pyridostigmine. Incidence and risk factors for time to conversion Over 258 patient-years (PY) of follow-up, 36 patients developed GMG. Overall incidence of GMG was 14 (95%CI, 10.09-19.4) per 100 PY. The median time of conversion from OMG to GMG in all patients was 4.97 years (Table 4). Female sex, history of smoking, and presence of thymic abnormalities were associated with shorter median conversion time (2.94, 1.85, 1.25 years respectively) while patients who received immunosuppressive agents and pyridostigmine had longer median conversion time (12.49 years for both groups). Moreover, overall probability of conversion from OMG to GMG at 2 years was 0.37. Female sex, history of smoking, and presence of thymic abnormalities were associated with higher probability of conversion while receiving immunosuppressive agents and pyridostigmine were associated with lower probability of conversion at 2, 4, 6 years. Figure 2 shows KaplanMeier curves of each factors.
5 The results of Cox proportional hazard model were in agreement with those of logistic regression models, showing that female sex, history of smoking, and presence of thymic abnormality were associated with a conversion to GMG. Crude hazard ratio was 1.67 (95% CI, 0.82-3.42), 1.88 (95% CI, 0.92-3.86), and 2.19 (95% CI, 1.11-4.32) for female sex, history of smoking, and presence of thymic abnormality (Table 3). Adjusted hazard ratio was 2.52 (95% CI, 1.04-6.10), 3.42 (95% CI, 1.40-8.45), and 1.82 (95% CI, 0.91-3.67) for female sex, history of smoking, and presence of thymic abnormality subsequently. Receiving immunosuppressive agents and pyridostigmine were associated with lower rate of conversion using Cox proportional hazard ratio. Crude hazard ratio was 0.29 (0.15, 0.60) and 0.22 (0.10, 0.46) for immunosuppressive agents and pyridostigmine, respectively. Adjusted hazard ratio was 0.42 (95% CI, 0.19-0.97) and 0.37 (95% CI, 0.14-0.93) for immunosuppressive agents and pyridostigmine, respectively. Discussion In this study, the demographic and clinical factors were evaluated whether they have any relationship with the conversion to GMG among patients with AchR Ab seropositive OMG. Previous studies was in agreement with our study in term of female sex 4 and presence of thymic abnormalities 2, 3, 9, 10 as factors associated with higher rate of conversion to GMG, whereas receiving immunosuppressive agents including systemic corticosteroid was reported as a protective factor and may delay time to the conversion in several studies.3, 9, 11, 12 Table 5 summarizes the results of previous studies investigating conversion of OMG to GMG in different settings. Although most previous studies were performed in both seropositive and seronegative myasthenia patients, Mee et al. 13 investigated the effect of immunotherapy (prednisolone and thymectomy) in their retrospective study of 21 AchR Ab seropositive patients who experienced conversion of OMG to GMG and reported that immunotherapy might prevent conversion in AchR Ab seropositive patients. The population in their study was similar to the population in our study (i.e., only AchR Ab seropositive patients included) and the results from our study was in agreement with their findings in term of receiving immunosuppressive agents as a protective factor. However, there has been no previous study reporting the history of smoking as a risk factor and receiving pyridostigmine as a protective factor of conversion. Our study is the first to show that smoking is a risk factor for a conversion to GMG. Our observed evidence that smoking increased a risk of conversion might be explained by increased autoimmune activities through recruitment of various types of immune cells and inflammatory cytokines induced by smoking as seen in many autoimmune disorder models8 It has been well accepted that smoking increases risk of developing thyroid eye disease (TED) and smokers have higher TED severity. 14 Since TED and myasthenia gravis could coexist, 15 smoking might affect natural history of myasthenia gravis as well. Alternative possible explanation is systemic acetylcholine receptor desensitization caused by long contact of blood nicotine to the whole-body acetylcholine receptor.8, 16 In addition to the previous studies, we emphasize that smoking not only worsens myasthenia gravis activities but also increases the risk of generalization among AchR Ab seropositive patients. Myasthenia
6 patients should be recommended to stop smoking in order to reduce the chance of conversion to GMG and improve both ocular and systemic symptoms. In this study, we found that pyridostigmine use was associated with lower rate of conversion to GMG. Pyridostigmine has been believed to have no effect to the natural history of the disease.1 Its inhibiting effect on acetylcholinesterase results in an increasing level of acetylcholine in the synaptic junction. As a result, pyridostigmine relieves the symptoms of myasthenia gravis. However, pyriostigmine may provide immunomodulatory effect that prevents conversion of OMG to GMG through a cholinergic anti-inflammatory pathway (CAP). Evidence from animal models showed circulating macrophages expressing α7 nicotinic acetylcholine receptor (α7 nAChR) interacts with serum acetylcholine to suppress production of inflammatory cytokines including tumor necrosis factor α, high mobility group boxes of protein (HMGB), and interleukin 6 (IL-6). CAP can be terminated by erythrocyte-bound acetylcholinesterase. Acetylcholinesterase inhibitors, hence, have been proposed to have immunemodulatory effects via CAP activation in addition to their primary action.17 A couple studies reported that HMGB, and IL-6 were involved in immune process in myasthenia gravis.18, 19 Moreover, AchR Ab seropositive patients with GMG had higher serum HMGB level than patients with OMG and control.18 The strength of our study is that we included only definite myasthenia gravis patients diagnosed by positive AchR Ab. The population in our study was not contaminated by subjects diagnosed by other diagnostic modules (e.g. electromyography or responsiveness to acetylcholinesterase inhibitor), which may have more false positive rate. On the other hand, the results from this study might not be able to be generalized to AchR Ab seronegative myasthenia gravis, which is one of our limitations. The other potential limitations included small number of subjects and missing data from old medical records. We are aware that these limitations are the common nature of retrospective study and suggest a larger cohort study with longer follow-up time to investigate the risk and protective factors of conversion to GMG as a future study. Also, it might be interesting to investigate further whether a combination of pyridostigmine and immunosuppressive agents is beneficial. In conclusion, pyridostigmine, currently used as a symptomatic treatment of OMG and immunosuppressive agents showed protective effect to conversion to GMG, and smoking, in addition to presence of thymic abnormalities and female gender may accelerate conversion to GMG. OMG patients should be informed that pyridostigmine or immunosuppressive agents including corticosteroid might be potential treatment option to prevent conversion. Moreover, they should be encouraged to stop smoking in order to reduce the rate of disease progression to GMG, thus saving the patients from extreme burden of muscle weakness, bulbar symptoms, or even life-threatening respiratory failure. Acknowledgements a. Funding/supports: none
7 b. Financial disclosures: All authors have no financial disclosures. c. Other acknowledgements: We would like to thank Abhinbhen Saraya Wasontiwong, MD, MSc for providing data from the database of Neuroscience Laboratory, Thai Red Cross Emerging Infectious Disease Health Science Center, King Chulalongkorn Memorial Hospital.
8 References 1. Vaphiades MS, Bhatti MT, Lesser RL. Ocular myasthenia gravis. Curr Opin Ophthalmol 2012;23(6):537-542. 2. Wong SH, Petrie A, Plant GT. Ocular Myasthenia Gravis: Toward a Risk of Generalization Score and Sample Size Calculation for a Randomized Controlled Trial of Disease Modification. J Neuroophthalmol 2016;36(3):252258. 3. Hong YH, Kwon SB, Kim BJ, et al. Prognosis of ocular myasthenia in Korea: a retrospective multicenter analysis of 202 patients. J Neurol Sci 2008;273(1-2):10-14. 4. Mazzoli M, Ariatti A, Valzania F, et al. Factors affecting outcome in ocular myasthenia gravis. Int J Neurosci 2018;128(1):15-24. 5. Wang L, Zhang Y, He M. Clinical predictors for the prognosis of myasthenia gravis. BMC Neurol 2017;17(1):77. 6. Bever CT, Jr., Aquino AV, Penn AS, Lovelace RE, Rowland LP. Prognosis of ocular myasthenia. Ann Neurol 1983;14(5):516-519. 7. Maniaol AH, Boldingh M, Brunborg C, Harbo HF, Tallaksen CM. Smoking and socio-economic status may affect myasthenia gravis. Eur J Neurol 2013;20(3):453-460. 8. Gratton SM, Herro AM, Feuer WJ, Lam BL. Cigarette Smoking and Activities of Daily Living in Ocular Myasthenia Gravis. J Neuroophthalmol 2016;36(1):37-40. 9. Li F, Hotter B, Swierzy M, Ismail M, Meisel A, Ruckert. Generalization after ocular onset in myasthenia gravis: a case series in Germany. J Neurol 2018;265(12):2773-2782. 10. Teo KY, Tow SL, Haaland B, et al. Low conversion rate of ocular to generalized myasthenia gravis in Singapore. Muscle Nerve 2018;57(5):756760. 11. Kupersmith MJ, Latkany R, Homel P. Development of generalized disease at 2 years in patients with ocular myasthenia gravis. Arch Neurol 2003;60(2):243-248. 12. Sommer N, Sigg B, Melms A, et al. Ocular myasthenia gravis: response to long-term immunosuppressive treatment. J Neurol Neurosurg Psychiatry 1997;62(2):156-162. 13. Mee J, Paine M, Byrne E, King J, Reardon K, O'Day J. Immunotherapy of ocular myasthenia gravis reduces conversion to generalized myasthenia gravis. J Neuroophthalmol 2003;23(4):251-255. 14. Prummel MF, Wiersinga WM. Smoking and risk of graves’ disease. JAMA 1993;269(4):479-482. 15. Bojikian KD, Francis CE. Thyroid eye disease and myasthenia gravis. Int Ophthalmol Clin 2019;59(3):113-124. 16. Moreau T, Vandenabeele S, Depierre P, Confavreux C. Nicotinesensitive myasthenia gravis. Lancet 1995;345(8941):61-62. 17. Pohanka M. Inhibitors of acetylcholinesterase and butyrylcholinesterase meet immunity. Int J Mol Sci 2014;15(6):9809-9825. 18. Uzawa A, Kawaguchi N, Kanai T, Himuro K, Kuwabara S. Serum high mobility group box 1 is upregulated in myasthenia gravis. J Neurol Neurosurg Psychiatry 2015;86(6):695-697. 19. Zhang GX, Navikas V, Link H. Cytokines and the pathogenesis of myasthenia gravis. Muscle Nerve 1997;20(5):543-551.
9 20. Kamarajah SK, Sadalage G, Palmer J, Carley H, Maddison P, Sivaguru A. Ocular presentation of myasthenia gravis: A natural history cohort. Muscle Nerve 2018;57(4):622-627. Figure Legends Figure 1. Study flow chart. Figure legend: AchR Ab, acetylcholine receptor antibody; OMG, ocular myasthenia gravis; GMG, generalized myasthenia gravis Figure 2. Kaplan Meier Curves by demographic and clinical factors associated with conversion to generalized myasthenia gravis
Table 1 Characteristic of patients with and without conversion to generalized myasthenia gravis Total (N=105) Characteristics Age at onset of OMG (mean, SD) Duration of follow up in years (median, IQR)
Remained OMG (N=47) 54.4 (17.6)
GMG (N=58)
Remained OMG (N=35)
GMG (N=36)
50.3 (14.3)
54.4 (17.9)
50.5 (13.8)
4.91 (2.98, 6)
0.78 (0.18, 2.47)
NA N(%)
Complete casesa (n=71)
N(%)
N(%)
N(%)
Sex Female Male History of smoking
28 (59.6%) 19 (40.4%) 6 (14.6%)
42 (72.4%) 16 (27.6%) 13 (33.3%)
18 (51.4%) 17 (48.6%) 5 (14.3%)
25 (69.4%) 11 (30.6%) 11 (30.6%)
Presence of ptosis
45 (95.7%)
57 (98.3%)
33 (94.3%)
36 (50.7%)
Presence of diplopia
29 (61.7%)
44 (75.9%)
24 (68.6%)
28 (77.8%)
Positive RNS
14 (46.7%)
23 (69.7%)
11 (47.8%)
17 (73.9%)
44 (93.6%)
43 (74.1%)
33 (94.3%)
26 (72.2%)b
27 (57.5%)
22 (37.9%)
23 (65.7%)
13 (36.1%)b
6 (15.8%)
23 (42.6%)
5 (14.3%)
14 (38.9%)b
13 (27.7%)
12 (55.2%)
11 (31.4%)
6 (16.7%)
Received pyridostigmine Received immunosuppressive agentsc Presence of thymic abnormalities Presence of other autoimmune disorders
GMG, generalized myasthenia gravis; OMG, ocular myasthenia gravis; RNS , repetitive nerve stimulation test; SD, standard deviation; IQR, interquartile range; NA, not available a number of patients who had complete information of all factors of interest b p<0.05 c including systemic corticosteroid
Table 2 Risk and protective factors for conversion to generalized myasthenia gravis (N = 71) Characteristics Female Diplopia (having Diplopia) Age of onset of ocular myasthenia Smoking status Thymic abnormality Received immunosuppressive agents Received pyridostigmine
Crude Odds Ratio (95%CI) 2.15 (0.81, 5.67) 1.60 (0.55, 4.64) 0.98 (0.96, 1.01)
Adjusteda Odds Ratio (95% CI) 4.02 (0.62, 18.72)b -
2.64 (0.81, 8.62) 3.82 (1.20, 12.18) 0.29 (0.11, 0.78)
6.13 (1.13, 33.23)c 4.13 (1.09, 15.67)c 0.47 (0.14, 1.59)
0.16 (0.032, 0.78)
0.23 (0.04, 1.53)
Reference groups: no smoking, no thymic abnormality, did not receive immunosuppressive agents, did not receive pyridostigmine, no diplopia, being male 95% CI, 95% Confidence Interval Adjusted model includes sex, smoking status, thymic abnormality, received immunosuppressive agents, and received pyridostigmine b p-value = 0.064 c p-value < 0.05 a
Table 3 Hazard ratios of conversion to generalized myasthenia gravis (N = 71) Risk factors
Crude HR (95%CI)
Female Male Smoking Non-smoker Thymic abnormality No thymic abnormality Received immunosuppressive agents Not received Received pyridostigmine Not received
1.67 (0.82, 3.42) 1.0 1.88 (0.92, 3.86) 1.0 2.19 (1.11, 4.32) 1.0 0.29 (0.15, 0.60)
Adjusted HR (95%CI) 2.52 (1.04, 6.10) 1.0 3.42 (1.40, 8.45) 1.0 1.82 (0.91, 3.67) 1.0 0.42 (0.19, 0.97)
1.0 0.22 (0.10, 0.46) 1.0
1.0 0.37 (0.14, 0.93) 1.0
HR, hazard ratio; 95% CI, 95% Confidence Interval
1 Table 4 Median conversion time and probability of conversion by risk factors Median conversion time (years, SE)
Probability of conversion at various years (95% CI) 2 years
4 years
6 years
4.97 (2.33)
0.37 (0.27, 0.49)
0.49 (0.38, 0.62)
0.55 (0.42, 0.68)
Sex Male Female
NA 2.94 (1.63)
0.25 (0.13, 0.45) 0.45 (0.31, 0.60)
0.44 (0.27, 0.66) 0.53 (0.39, 0.69)
0.44 (0.27, 0.66) 0.62 (0.46, 0.78)
Smoking status Yes No
1.85 (0.45) 12.49 (4.90)
0.52 (0.30, 0.78) 0.33 (0.22, 0.47)
0.76 (0.52, 0.94) 0.42 (0.30, 0.56)
0.76 (0.52, 0.94) 0.49 (0.35, 0.65)
1.25 (0.82) NA
0.53 (0.33, 0.76) 0.31 (0.20, 0.46)
0.72 (0.50, 0.91) 0.41 (0.28, 0.56)
0.72 (0.50, 0.91) 0.49 (0.35, 0.66)
0.14 (0.06, 0.30) 0.61 (0.45, 0.77)
0.34 (0.20, 0.53) 0.64 (0.48, 0.80)
0.40 (0.24, 0.61) 0.72 (0.53, 0.88)
0.27 (0.18, 0.41) 0.83 (0.59, 0.97)
0.42 (0.30, 0.57) 0.83 (0.59, 0.97)
0.50 (0.36, 0.66) 0.83 (0.59, 0.97)
Overall
Thymic abnormality Yes No Received immunosuppressive Agents Yes No Received pyridostigmine Yes No
12.49 (0.45) 1.13 (0.63)
12.49 (4.59) 0.08 (0.07)
SE, standard error; 95% CI, 95% Confidence Interval; NA, not available
2
Table 5 Summary of previous studies of risk factors associated with conversion to generalized myasthenia gravis Year
N
Country
1983
108
USA6
1997
78
Germany12
2003
147
USA11
2008
202
Korea3
2016
101
UK2
Diagnostic criteria Conver sion rate 49% • Edrophonium and neostigmine test 31% • AchR Ab • RNS • Clinical signs with: Edrophonium test and treatment response 18.1% • Clinical signs with Edrophonium test 23.3% • Edrophonium test • AchR Ab • RNS • SFEMG 31% • Edrophonium test • Serology test • EMG • Clinical presentation
Median time to conversion <1 year
Risk factors
Protective factors
None
Increased duration of pure OMG
24.5 months
Mild symptoms Normal RNS Low or absent AchR Ab Receiving inmmunosuppressive agents
2 years
AchR Ab seropositive
Prednisone treatment
NA
AchR Ab seropositive Thymoma
Early oral prednisolone treatment
1.31 years
AchR Ab or anti-MuSK seropositive Presence of 1 or more comorbidities
Thymic hyperplasia AchR Ab seropositive Disease onset < 50 years
2017
93
UK20
• Edrophonium test • AchR Ab seropositive • SFEMG • Responsive to ice pack test, pyridostigmine
47.3%
7 months
2017
168
Italy4
• Edrophonium test • AchR Ab, antiMuSK seropositive • SFEMG • RNS • Responsive to pyridostigmine
18.4%
NA
Female sex AchR Ab seropositive
2017
40
China5
• AchR Ab seropositive • SFEMG • RNS • Responsive to pyridostigmine
85%
Mostly < 6 months
Older age of onset
2018
180
Germany9
23.6 months
Thymoma
• AchR Ab seropositive • Anti-MuSK
61.1%
Corticosteroid treatment
seropositive • SFEMG • RNS • Responsive to therapy 10.6% AchR Ab 2018 155 Singapore10 • Edrophonium seropositive test Thymoma • AchR Ab Positive RNS seropositive • SFEMG • RNS • Responsive to pyridostigmine OMG, ocular myasthenia gravis; AchR Ab, acetylcholine receptor antibody; RNS, repetitive nerve stimulation test; SFEMG, singlefiber electromyography; EMG, electromyography; anti-MuSK, anti-muscle specific tyrosine kinase