Autoimmunity in ocular and generalised myasthenia gravis

Thyroid eye disease and ocular myasthenia gravis

PURPOSE OF REVIEW

An overview of two ocular diseases, which significantly impact quality of life: thyroid eye disease (TED) and ocular myasthenia gravis (OMG). Additionally, we describe the clinical challenge when they occur simultaneously. We will describe the pathophysiology of both conditions, the currently available diagnostic tools, and the therapies available.

RECENT FINDINGS

Recent literature has described newer diagnostic modalities, predictors of disease severity and co-occurrence of TED and OMG, and novel therapies. There is also critical analysis of current therapeutics and risk factors.

SUMMARY

The findings from this review suggest a need for heightened clinical awareness and early detection strategies for TED and OMG due to their overlapping clinical presentation. Emerging therapies and diagnostic techniques should be integrated into practice. Further research is warranted to explore the long-term safety and efficacy of novel treatments and the potential genetic links between these conditions.

Disappearance of Anti-Thyroid Autoantibodies following Thymectomy in Patients with Myasthenia Gravis

OBJECTIVES

The thymus plays a central role in immune tolerance, which prevents autoimmunity. Myasthenia gravis (MG) is commonly associated with thymoma or thymus hyperplasia, and it can coexist with autoimmune thyroid diseases. However, the role of the thymus in thyroid autoimmunity remains to be clarified, which we investigated here.

STUDY DESIGN

The study design entailed the inclusion of consecutive MG patients and the measurement of anti-thyroid autoantibodies at baseline and, limited to autoantibody-positive patients, also at 24 and 48 weeks. One hundred and seven MG patients were studied. The main outcome measure was the behaviour of anti-thyroglobulin autoantibodies (TgAbs) and anti-thyroperoxidase autoantibodies (TPOAbs) over time in relation to thymectomy.

RESULTS

Serum TgAbs and/or TPOAbs were detected in ∼20% of patients in the absence of thyroid dysfunction. The prevalence of positive serum TgAbs and/or TPOAbs decreased significantly (p = 0.002) over the follow-up period in patients who underwent thymectomy, but not in patients who were not thymectomized. When the analysis was restricted to TgAbs or TPOAbs, findings were similar. On the same line, there was a general trend towards a reduction in the serum concentrations of anti-thyroid autoantibodies in patients who underwent thymectomy, which was significant for TPOAbs (p = 0.009).

CONCLUSIONS

Our findings suggest a role of the thymus in the maintenance of humoral thyroid autoimmunity.

Challenges in diagnosing coexisting ocular myasthenia gravis and thyroid eye disease

Ocular myasthenia gravis (OMG) and thyroid eye disease are two autoimmune conditions that have several overlapping clinical features, and these coexist with a small but not insignificant frequency. Segregating these diagnoses is typically straightforward, but, when the two diseases co-occur in the same individual, making a diagnosis of OMG can be very challenging. In this review we address what is known about the coexistence of OMG and thyroid eye disease and we highlight the clinical features that are suggestive of overlapping conditions. We also describe the major testing approaches used in the diagnosis of these two entities, with special emphasis on the potential shortcomings of individual tests in patients with overlapping disease. In patients with thyroid eye disease, securing a diagnosis of OMG may not be possible on the basis of a single positive test. A multimodal approach using clinical, serologic, imaging, and electrodiagnostic data, is typically required.

Concurrence of Myasthenia Gravis and Thyroid Disorders: A Retrospective Database Study

Introduction

Both myasthenia gravis (MG) and autoimmune thyroid diseases (AITDs) are autoimmune diseases. Graves’disease (GD) is the most common AITD reported to be associated with MG. Currently, there is limited data on prevalence and clinical features/outcomes of MG in various thyroid diseases in a large database report.

Methodology

A total of 872 patients with MG and 97,251 patients with thyroid disorders had been recorded by the tertiary hospital database. The study period was between 1997 and 2017. Patients with a thyroid disorder and MG were identified by the ICD-10-CM code. Clinical courses of MG accompanied by thyroid disorders were studied.

Results

During the 20-year study period, there were 872 patients with MG and 97,251 patients with thyroid disorders. In the group with thyroid disorders, 28,886 patients (29.70%) had GD, 1,612 patients (1.66%) had Hashimoto's thyroiditis (HT), 13,172 patients (13.54%) had toxic goiter and 53,581 patients (55.10%) had nontoxic goiter. Ninety-seven patients had been diagnosed with both MG and thyroid disorders. Among the four types of thyroid disorders, the rate of MG was highest in HT group (9.92/1,000 HT patients). There were four significant factors among four groups of thyroid disorders including age of onset of thyroid disease (p 0.004), MG classification (p<0.001), MG treatment (p<0.001), and thymic pathology (p 0.034). Among the four groups of thyroid disorders, patients with MG and HT were diagnosed with thyroid disease at the youngest age (27 years) compared with other thyroid diseases. Additionally, the MG patients with HT also had the highest proportion of MG class 4-5 a/b (7 patients, 43.75%), received prednisolone treatment (15 patients, 93.75%), received immunosuppressants (9 patients, 56.25%), received IVIG or PLEX (5 patients, 31.30%), and had thymoma (6 patients, 46.15%).

Conclusion

MG is most prevalent in patients with HT. Patients with both MG and HT had more severe MG status and had higher rate of thymoma.

Ocular Myasthenia Gravis: Toward a Risk of Generalization Score and Sample Size Calculation for a Randomized Controlled Trial of Disease Modification

BACKGROUND

There is currently no prognostic test to determine the risk of developing generalized myasthenia gravis (GMG) risk in patients who first present with ocular disease. Most studies that report risk factors are flawed by the inclusion of patients on immunosuppression, which is likely to reduce the risk.

OBJECTIVE

To create a prognostic score to predict the risk of GMG.

METHODS

Multicenter retrospective cohort of patients with ocular myasthenia gravis for minimum 3 months, untreated with immunosuppression for minimum 2 years or until GMG onset.

RESULTS

One hundred one (57 female) patients were included, with median follow-up of 8.4 years (2-42) from disease onset. Thirty-one developed GMG at median of 1.31 years (3.5 months-20.2 years); 19 occurred within 2 years. Univariable logistic regression analysis produced 3 significant predictors (P < 0.10), adjusted odds ratios in a multivariable logistic model (χ P = 0.01) with multiple imputations for missing data: seropositivity, 5.64 (95% CI, 1.45-21.97); presence of 1 or more comorbidities including autoimmune disorders, 6.49 (95% CI, 0.78-53.90); thymic hyperplasia, 5.41 (95% CI, 0.39-75.43). Prognostic score was derived from the coefficients of the logistic model: sum of the points (1 point for the presence of each of the above predictive factors), classified "low risk" if ≤1 and "high risk" if ≥2. Predicted probabilities were 0.07 (SD, 0.03) for low risk and 0.39 (SD, 0.09) for high risk. Negative predictive value was 91% (95% CI, 79-98), positive predictive value was 38% (95% CI, 23-54), sensitivity was 79% (95% CI, 54-94), specificity was 63% (95% CI, 50-74), area under receiver operating characteristic curve was 0.74 (95% CI, 0.64-0.85).

CONCLUSIONS

In this preliminary study, we have shown by proof of principle that it is possible to stratify risk of GMG: an approach that may allow us to better counsel patients at diagnosis, complement decision-making, and move us toward addressing the question of modifying GMG risk in high-risk patients. Furthermore, the effect of comorbidities is novel and demands further elucidation.

Relationship Between Age, Gender, and Race in Patients Presenting With Myasthenia Gravis With Only Ocular Manifestations

BACKGROUND

The demographic associations among patients presenting with myasthenia gravis with only ocular manifestations (OMG) is not clear.

METHODS

In this 5-center case series, we collected the race, gender, and age at diagnosis of patients diagnosed with myasthenia gravis who had no signs or symptoms of generalized myasthenia gravis (GMG). An a priori sample size calculation determined that 140 patients were required to accept that there was a ≤10-year difference in mean age (equivalence testing: power 90%, α = 0.05). Robust Bayesian analysis and linear regression were applied to evaluate whether age differed by gender or race.

RESULTS

Of 433 patients included, 258 (60%) were men. Mean age among men was 57 years (SD = 19) and 52 years (SD = 21) among women. The 95% credible interval (CI) (Bayesian equivalent of confidence interval) was 0.8-8.7 years for mean age, and there was a 99.6% probability that the mean difference in age between sexes was <10 years. Race was documented in 376 (68 [18%] non-Caucasian). Caucasians were 17.3 years older than non-Caucasians at diagnosis (95% CI, 12.2-22.3 y; P < 0.001) controlling for gender. There was no additive interaction of gender and race (P = 0.74). There was a bimodal distribution for women peaking around 30 and 60 years. Men had a left skewed unimodal age distribution peaking at age 70.

CONCLUSIONS

The distribution of age at presentation in patients with OMG is different between men and women, similar to GMG. Non-Caucasian patients tend to develop OMG at a younger age.

Prevalence and impact of autoimmune thyroid disease on myasthenia gravis course

OBJECTIVES

Autoimmune thyroid diseases (ATDs) frequently accompany myasthenia gravis (MG) and may influence its course. We aimed to determine the association and impact of ATD with early- (<50 years), late-onset MG, or thymoma-MG.

MATERIALS AND METHODS

Prevalence of ATD was measured in a cross-sectional study of 343 consecutive patients with MG (236 F, 107 M) aged 4-89 years; 83.8% were seropositive, in 2.9%, anti-MuSK antibodies were detected. Concentrations of antithyroid peroxidase antibodies, antithyroglobulin antibodies, antithyrotropin receptor antibodies, and TSH level were measured in all patients. MG clinical course, treatment received, and treatment results were evaluated.

RESULTS

Autoimmune thyroid diseases were diagnosed in 92 (26.8%) of MG patients including 4.4% with Graves (GD), 9% with Hashimoto thyroiditis (HT), and 13.4% with antithyroid antibodies only. GD patients had ocular symptoms more often than patients with antithyroid antibodies or HT (p = .008). ATD prevalence was comparable in MG with early and late onset, while non-ATDs were more frequent in thymoma-MG (p = .049). Immunosuppressive therapy was less frequently needed in the patients with MG and ATD, indirectly indicating milder MG course (p = .005). Risk of myasthenic crisis and the results of treatment did not differ between patients with and without ATD.

CONCLUSIONS

Autoimmune thyroid diseases are frequently accompanied by early-and late-onset MG, while thymoma-MG is related to higher risk of non-ATD. Myasthenia coexisting with ATD follows milder course than MG alone.

Complicating autoimmune diseases in myasthenia gravis: a review

Myasthenia gravis (MG) is a rare autoimmune disease of skeletal muscle endplates. MG subgroup is relevant for comorbidity, but usually not accounted for. MG patients have an increased risk for complicating autoimmune diseases, most commonly autoimmune thyroid disease, systemic lupus erythematosus and rheumatoid arthritis. In this review, we present concomitant autoimmune disorders associated with the different MG subgroups, and show how this influences treatment and prognosis. Concomitant MG should always be considered in patients with an autoimmune disorder and developing new neuromuscular weakness, fatigue or respiratory failure. When a second autoimmune disorder is suspected, MG should be included as a differential diagnosis.

Ocular myasthenia gravis in a setting of thyrotoxicosis

Ocular myasthenia gravis in conjunction with thyroid disorders, although rare, has been reported in the past. However, the similarity in the presentation of both the entities and the tendency of myasthenia gravis to get overlooked easily, even by experienced clinicians, necessitates a thorough knowledge, a strong consideration, and a vigilant approach, to aid in its diagnosis. We discuss a case of a female in a thyrotoxic state, with symptoms of ocular myasthenia gravis, and a brief overview of this entity.

Clinical features of myasthenia gravis patients with autoimmune thyroid disease in Taiwan

OBJECTIVES

The aim of this study was to analyze the prevalence and clinical features of myasthenia gravis (MG) patients with and without autoimmune thyroid disease (ATD).

MATERIALS AND METHODS

Between 1999 and 2009, we reviewed a total of 1482 patients with MG. On the basis of thyroid evaluations, as well as neurological, clinical, and serological findings, the patients were divided into group A (MG patients with ATD) or group B (MG patients without ATD). The patients were categorized as having ocular myasthenia when symptoms restricted to the ocular system were present for 2 years or more.

RESULTS

Of the 1482 MG patients, 121 (8.2%) patients were classified into group A. Graves' disease was more predominant (5.7%) than Hashimoto's thyroiditis (1.1%) and antibody-positive thyroid disease (1.4%). MG patients with ATD were predominantly female, were younger at the onset of MG symptoms, had a higher frequency of mild MG (ocular and mild generalized MG) and thymic hyperplasia, and had lower levels of seropositive anti-acetylcholine receptor antibodies. Compared to patients without thyroid eye disease, ATD patients with thyroid eye disease had a higher frequency of ocular MG.

CONCLUSIONS

This is the largest review of the clinical features of MG patients with and without ATD to date. We found that compared to ocular MG, mild MG is more commonly associated with ATD. Furthermore, we observed that thymic hyperplasia is more common in MG patients with ATD, while thymoma is more common in MG patients without ATD.

Functional interleukin-17 receptor A are present in the thyroid gland in intractable Graves disease

Th17 lymphocytes and its main cytokine, IL-17, play an important role in autoimmune thyroid diseases, such as intractable Graves disease (GD). IL-17 signals are transmitted through its receptor, IL-17RA. The intrathyroid expression of IL-17RA in intractable GD is not understood. In this study, ELISA was used to measure serum IL-17 levels in patients with untreated GD, intractable GD or GD in remission and healthy controls. Real-time PCR, flow cytometry and immunofluorescence staining evaluated IL-17RA mRNA and protein expression in thyrocytes. IL-6, chemokine ligand 10 (CXCL10) and intercellular adhesion molecule (ICAM)-1 expression was measured in IL-17-stimulated thyrocyte cultures to evaluate the functional status of IL-17RA. Our data indicates that serum IL-17 levels are significantly increased in intractable GD and affected thyrocytes show functional IL-17R expression. These changes facilitate the IL-17-mediated upregulation of IL-6, CXCL10, and ICAM-1. The IL-17/IL-17R interaction could be a potential target for therapeutic interventions in intractable GD.

Does myasthenia gravis provide protection against cancer?

OBJECTIVES

Reports have been made of an altered rate of extrathymic malignancies in patients with myasthenia gravis (MG). This study compared the rate of such malignancies in a group of MG patients with an optimal control group.

MATERIALS AND METHODS

From the Norwegian Cause of Death Registry, we identified 249 dead MG patients (1951-2001) and a control group of 1,245 individuals (five per patient) dead in the same period, matched for sex and year of birth.

RESULTS

Patients with MG had a lower occurrence of malignant disease as underlying or contributing cause of death than the controls (8.8% vs 27.2%, P < 0.001). The main difference was found for colorectal cancer, breast cancer and cancer in the upper digestive tract (esophagus and stomach).

CONCLUSIONS

We report a significantly lower rate of extrathymic malignancies in patients with MG than in controls, and we hypothesize that MG treatment or the immunological mechanisms involved in MG may protect patients with MG from developing an extrathymic malignancy.

Associated conditions in myasthenia gravis: response to thymectomy

To compare the response of thymectomy in patients with associated conditions (PWAC) and without associated conditions (PWOAC). Comparative, retrospective. 198 patients with the established diagnosis of myasthenia gravis who had a thymectomy between 1987 and 2000, and who were folowed up for at least 3 years. We formed two groups, one with associated conditions and the second without associated conditions. The patients were divided into four groups: (i) patients in remission, (ii) patients with improvement, (iii) patients without changes, and (iv) patients whose condition worsened. Associated conditions (AC) were found in 49 patients (26%). The main associated conditions were hyperthyroidism in 16 patients (33%) hypothyroidism in seven (14%), rheumatoid arthritis in five (10%) and hypothyroidism and Sjogren syndrome in three (6%). Concerning the response of thymectomy, 13 patients WAC showed remission (27%), vs. 54 patients WOAC (39%). Twenty patients WAC showed improvement (41%) vs. 46 WOAC (33%). Thirteen patients WAC had no changes (27%) vs. 37 WOAC (26%). Finally, in three patients WAC their condition worsened (6%) vs. three WOAC (2%). The response to thymectomy was high (69%) in both groups. We did not identify significant differences.

Laryngeal Myasthenia Gravis: Report of 40 Cases

Myasthenia gravis, an autoimmune disorder of the neuromuscular junction, is usually recognized because of ocular complaints or generalized weakness. We report a series of 40 patients who presented with dysphonia as their initial and primary complaint. Diagnostic testing included strobovideolaryngoscopy, electromyography (EMG) with repetitive stimulation and Tensilon testing, and laboratory and radiographic evaluation. Strobovideolaryngoscopy most commonly revealed fluctuating impairment of vocal fold mobility, either unilateral or bilateral. EMG detected evidence of neuromuscular junction abnormalities in all patients. Only one patient had evidence of antiacetylcholine receptor (ACh-R) antibodies, but many other abnormalities suggestive of autoimmune dysfunction were present. Pyridostigmine therapy was initiated in 34 patients but was not tolerated in 4. Of the remaining 30 patients, 23 reported improvement of symptoms. We conclude that myasthenia gravis can present with symptoms confined primarily to the larynx and should be included in the differential diagnosis of dysphonia.

Myasthenia gravis with ocular involvement in older patients

BACKGROUND

There has been little previous study reporting the eye findings and presentation of elderly patients with myasthenia gravis. The purpose of this study was to review the findings and course of myasthenia gravis after the sixth decade of life.

METHODS

Retrospective observational case series. The authors reviewed the clinical records of 27 patients with onset of myasthenia gravis at age 60 years or more who were seen at a tertiary care academic ophthalmology centre in Houston between January 1992 and March 1999. The diagnosis of myasthenia gravis was based on conventional clinical and laboratory criteria.

RESULTS

Twenty patients (74%) were men. Of the 16 patients who underwent testing for anti-acetylcholine receptor antibodies, 11 (69%) were seropositive. Concurrent thyroid disease was found in seven patients (26%), including five (71%) of the seven women. No patient had thymoma. Sixteen patients (59%) manifested generalized symptoms during follow-up; 12 did so within 1 year of disease onset. Patients responded well to both anticholinesterase and corticosteroid therapy. At the most recent follow-up visit 18 patients (67%) were clinically improved, and no patient was clinically worse.

INTERPRETATION

Myasthenia gravis in this study was characterized by a male predominance, high rate of concurrent thyroid disease, high rate of progression to mild generalized symptoms, absence of thymoma, good response to medical therapy and minimal life-threatening complications. Clinicians should consider the diagnosis of myasthenia gravis in an older patient presenting with diplopia or ptosis.

Myasthenia gravis and associated autoimmune diseases in children

Myasthenia gravis has been associated with other autoimmune disorders. We report two children with myasthenia gravis and another autoimmune disease: an 18-month-old boy with ocular myasthenia gravis and Hashimoto's disease and a 14-year-old girl presenting with autoimmune polymyositis, then generalized myasthenia gravis 2 years later. The rare combinations of myasthenia gravis and Hashimoto's disease or polymyositis in children are discussed, and we also briefly review myasthenia gravis and other associated autoimmune diseases in children.

Increased frequency of euthyroid ophthalmopathy in patients with Graves' disease associated with myasthenia gravis

We previously showed that myasthenia gravis (MG) has a mild clinical expression when associated with autoimmune thyroid diseases (AITD). In the present study we have investigated the frequency of thyroid-associated ophthalmopathy (TAO) in patients with Graves' disease (GD) associated with MG as compared with GD patients without MG. A total of 418 patients with GD were studied, 31 with MG and 387 without MG. TAO was evaluated by physical examination, exophthalmometry, computerized tomography, and computerized visual fields assessment. The overall prevalence of TAO was similar in GD patients with MG (61.2%) and in those without MG (56.4%). When the analysis was restricted to GD patients with ocular MG, a greater frequency of TAO was found (84.6%), compared with GD patients without MG or with GD patients with generalized MG, although the differences did not reach the statistical significance. GD patients with MG had a significantly greater prevalence (12.9%) of euthyroid ophthalmopathy (clinically overt ophthalmopathy without previous and/or current hyperthyroidism) than those without MG (3.1%; p = 0.003). The results suggest a preferential association between the ocular manifestations of GD and MG, which may be due to immunological cross-reactivity against common autoimmune targets in the eye muscle as well as to a common genetic background.

Eye muscle antibodies in patients with ocular myasthenia gravis: possible mechanism for eye muscle inflammation in acetylcholine-receptor antibody-negative patients

Myasthenia gravis is an organ-specific autoimmune disorder generally thought to be caused by an antibody-mediated attack against the skeletal muscle nicotinic acetylcholine (Ach) receptor (AchR) at the neuromuscular junction. Extraocular muscle weakness and double vision are present in about 90% of patients with myasthenia gravis and are the predominant complaints in about 20% of patients, when the condition is called ocular myasthenia gravis (OMG). While serum antibodies against the AchR are detected in most patients with generalized myasthenia gravis (GMG), they are not found in about one-third of patients with the ocular variety, and epidemiological, clinical, and serological studies suggest that OMG and GMG are two separate diseases. Both forms of myasthenia gravis are sometimes associated with thyroid autoimmunity or thyroid-associated ophthalmopathy (TAO). We have therefore tested the sera of patients with GMG and OMG by Western blotting for antibodies against porcine eye muscle membrane proteins in general, and by enzyme-linked immunosorbent assays (ELISA) specifically for reaction with two skeletal muscle antigens which are prominent marker antigens for TAO, namely, the calcium-binding protein calsequestrin and the so-called "64-kDa protein." The 64-kDa protein has recently been identified as the flavoprotein subunit of mitochondrial succinate dehydrogenase. Patients with ophthalmopathy and myasthenia were excluded. Nine of the patients had associated Graves' hyperthyroidism without evident ophthalmopathy and one had Hashimoto's thyroiditis. Antibodies against porcine eye muscle membrane antigens of M(r) 15-110 kDa were detected in patients with GMG or OMG, one or more antibodies being detected in 100% of patients with GMG and in 88% of those with OMG. The most frequently found antibodies were those targeting eye muscle membrane proteins of 15, 67, and 110 kDa. Antibodies reactive with purified calsequestrin (63 kDa) were detected in 21% of patients with OMG but in no patient with GMG. Antibodies recognizing purified succinate dehydrogenase (67 kDa) were found in 42% of patients with OMG, in 100% (5 of 5) of patients with GMG, and in 48% of all patients with myasthenia gravis not associated with Graves' hyperthyroidism. There was no close correlation between any eye muscle-reactive antibody and antibodies against the AchR in either group of myasthenic patients. The findings support the notion that immunoreactivity against skeletal muscle proteins other than the AchR may play a role in the development of the muscle weakness in AchR antibody-negative patients with OMG and GMG, although it is unlikely that any of the antibodies demonstrated in this study are directly implicated. Similarly, while the demonstration of antibodies reactive with eye muscle antigens associated with TAO in patients with OMG raises the possibility that the link between the ocular lesions of myasthenia gravis and Graves' disease may be autoimmunity against a common antigen(s), it is more likely that both disorders are mediated by cytotoxic T cells recognizing another cell membrane antigen, such as the novel thyroid and eye muscle shared protein G2s, and that serum antibodies reactive with succinate dehydrogenase Fp subunit and calsequestrin are markers of an immune-mediated eye muscle reaction.

Associated autoimmune diseases in myasthenia gravis. A population-based study

During a comprehensive epidemiological study of myasthenia gravis (MG) in Western Denmark 1975-1989, we analyzed the occurrence, clinical characteristics and prognosis of associated autoimmune diseases (AAD) in MG patients. AAD were found in 20 of 212 incident cases (9%) and in 30 of 220 prevalent cases (14%). The most common diseases were: thyroid disorders and rheumatic arthritis. Clinically, it was not possible to identify a subgroup of MG patients with a higher risk of AAD. In most MG patients the AAD occurred before thymectomy. The severity of the AAD was not influenced by thymectomy. The remission rate was lower in MG patients with AAD than in MG patients without AAD suggesting that the autoimmune response in MG patients with AAD is more severe.

Immunogenetic heterogeneity and associated autoimmune disorders in myasthenia gravis: a population-based survey in the province of Ferrara, northern Italy

INTRODUCTION

The well-established relationship between myasthenia gravis (MG) and HLA antigens varies among different ethnic groups. In Caucasians B8 and/or DR3 alleles have been found associated with young MG women without thymoma and with high titres of acetylcholine-receptor antibody (AChR Ab). An increased frequency of haplotype HLA-A3, B7 and/or DR2 has been observed in older MG patients with low AChR Ab levels. So far, there is no convincing evidence for an association between a specific haplotype HLA and ocular MG or MG with thymoma. MG subjects often show other concurrent autoimmune disorders suggesting a more general inherited predisposition to autoimmunity. We performed a community-based study to verify the HLA-A, B, C, DR and DQ profile on ethnically homogeneous MG patients and with the aim to estimate the frequency of concurrent autoimmune diseases and to compare HLA phenotypes to autoimmune status in different MG patients groups.

METHODS

Forty-seven patients, living in the province of Ferrara, were followed-up in our neurologic department and typed for HLA Antigens. In addition a set of immunological laboratory tests was performed.

RESULTS

We found a trend towards an increased B8 and DR3 frequencies in total affected population; an association between B8 allele and early onset of generalized MG sustained by thymic hyperplasia. The DR3 allele is statistically associated with the presence of additional autoimmune disorders.

CONCLUSIONS

Our data support the hypothesis of a genetically-based heterogeneity of the disease and show an increased prevalence of associate autoimmune conditions in MG patients.

Autoantibodies in D-penicillamine-induced myasthenia gravis: a comparison with idiopathic myasthenia and rheumatoid arthritis

The distribution of autoantibodies was studied in patients with rheumatoid arthritis (RA) treated by D-penicillamine and who developed myasthenia gravis (MG). The anti-human acetylcholine receptor (AChR) antibodies were specifically associated with clinical symptoms of MG without any difference in the pattern of specificities in idiopathic (id-MG) or in induced MG (DPen-MG). Conversely, anti-nuclear antibodies were elevated in DPen-MG sera compared to id-MG sera (P less than 0.001) but were also compared to patients with RA treated by D-penicillamine (or thiopronine) and who did not develop MG. Anti-denatured DNA antibodies were enhanced in sera from treated patients, whether they had presented or not a MG disease. Anti-histone antibodies were associated with RA. These observations suggest that the immunological imbalance in RA patients, can be increased by a drug treatment which may trigger the appearance of a second autoimmune disease such as MG, where anti-AChR antibodies are associated with anti-nuclear antibodies.

Prevalence of autoantibodies to thyroperoxidase in patients with various thyroid and autoimmune diseases

An original radioimmunoassay for quantitation of circulating autoantibodies (aAb) to thyroperoxidase (TPO) proved to be well suited for large scale routine testing. The present study was aimed to assess the prevalence of aAb to TPO in patients with various thyroid and autoimmune disease and, for comparison, in women referred for reproductive disorders and indication of in vitro fertilization. Anti-TPO aAb were measured in sera from 32 healthy subjects and 262 patients thoroughly investigated for thyroid dysfunction. As determined in healthy subjects, the normal level of aAb to TPO in serum ranged from 0.30 to 3.07 mg/l (of affinity-purified) anti-TPO aAb. Anti-TPO and anti-MIC aAb levels were both normal in 115 patients and correlated well (r = 0.835, P less than 0.001) in the remaining 147 patients. Coexistence of normal level of anti-TPO aAb and abnormal level of anti-MIC aAb was found in 4 patients and ascribed to a lack of specificity or sensitivity of the test for anti-MIC aAb. Coexistence of abnormal level of anti-TPO aAb and normal level of anti-MIC aAb was found in 67 patients of whom 62 presented only slightly elevated (3.1 to 10.0 mg/l) anti-TPO aAb concentration; the 5 remaining patients, all with overt thyroid autoimmune disease, showed anti-TPO levels between 10.7 to 100.7 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Concomitant euthyroid Graves' ophthalmopathy and isolated ocular myasthenia gravis

A 44 year old diabetic woman presented with diplopia and bilateral ptosis and mild exophthalmos. The patient was clinically euthyroid, the baseline thyroid function tests were normal, but the thyroid stimulating hormone response to thyrotrophin releasing hormone was flat. Computed tomographic scan and magnetic resonance imaging of the orbits showed left medial and inferior rectus muscle thickening, more prominent on the left side, consistent with Graves' disease. The tensilon stimulation test resulted in resolution of the ptosis and partial improvement of the ophthalmoplegia. The single fibre electromyography was consistent with a defect in neuromuscular transmission. However, forced duction test was normal and anti-acetylcholine receptor antibodies were undetectable. Significant improvement of the extraocular muscle function and resolution of the right ptosis had resulted from anticholinesterase therapy. These findings and the clinical response to therapy were consistent with concomitant euthyroid Graves' ophthalmopathy and ocular myasthenia gravis. Coexistent isolated ocular myasthenia gravis and Graves' ophthalmopathy is rare and should be considered in patients with findings of ocular myasthenia and extraocular muscle dysfunction.

Anti-neuroblastoma antibodies in myasthenia gravis: clinical and immunological correlations

Forty-four of 109 myasthenia gravis (MG) patients (40%) had serum antibodies against human neuroblastoma cells (NBL). Anti-NBL antibodies were most frequent in the sera of MG patients who had either a hyperplastic thymus or a thymoma, clinically mild to moderately severe generalized MG, and a long disease duration (greater than or equal to 11 years). No correlation between individual anti-NBL antibody and anti-acetylcholine receptor (AChR) antibody titers was observed. Seven of the 19 patients negative for anti-AChR antibodies (37%) had anti-NBL antibodies in their sera. These findings provide further evidence for immunological heterogeneity in MG. In addition to the typical autoantibodies to the AChR, autoimmunization against neural antigens can frequently be detected in these patients.

Associated disorders in myasthenia gravis: autoimmune diseases and their relation to thymectomy

The prevalence of myasthenia gravis (MG) in the counties of Hordaland and Sogn & Fjordane on January 1, 1984 was 9.6 per 100,000 inhabitants. Other autoimmune diseases were found in 11 out of 48 MG patients. The occurrence of autoimmune thyroiditis (5 patients, 10.4%) and systemic lupus erythematosus (4 patients, 8.3%) in the MG patients was clearly higher than that reported in the general population. Rheumatoid arthritis was found in 2 patients (4.2%). The autoimmune diseases were mainly recorded among the nonthymectomized MG patients. In addition to those with definite diseases of autoimmune nature, 3 other MG patients had thyroid antibodies and 1 had antinuclear factor without clinical evidence of autoimmune disease. Seven MG patients (14.6%) had unspecific arthralgia during active periods of MG. Two MG patients had ankylosing spondylitis.

Antibodies against saline-soluble components of skeletal muscle in myasthenia gravis

Antibodies against phosphate-buffered-saline extracts (SE) of non-acetylcholine receptor (AChR) skeletal muscle antigens were found in patients with myasthenia gravis (MG). The antigenicity of SE was distributed in three fractions with molecular masses of over 200 kDa, 90-150 kDa and 7-14 kDa on gel filtration. These fractions shared common antigenicities. Further analysis of 90-150 kDa fractions on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed five major bands, ranging from 105 kDa to 275 kDa. The antibodies against SE were detected in 52% (58/112) of the MG patients; incidence and titres were higher in the thymoma group (n = 21; 90% and 0.872 respectively) than in the non-thymoma group (n = 91; 43% and 0.200, P less than 0.001). In patients without a thymoma, these antibodies were frequently observed in late-onset disease and the severe generalized form (P less than 0.01). In 4 of 7 ocular MG patients without anti-AChR antibodies, low but appreciable levels of anti-SE antibodies were found. In 73% (11/15) of generalized MG patients treated with prednisolone and thymectomy, anti-SE antibody titres changed in association with those of anti-AChR antibodies and with the clinical course. Both antibody titres increased synchronously in patients who developed crises.

Immunological responses in the eyelid and orbit

Immunological responses in the eyelid and the orbit are reviewed: (1) A local immune response is dependent on the presence of lymphoid tissue in an organ. Lymphoid tissue is found in the conjunctival fornices and in the lacrimal gland but not in the orbit. The eyelids also have lymphatic drainage into the local lymph nodes. A local immune response is found in the palpebral conjunctiva and in the lacrimal gland, measureable both as immunoglobulin or specific antibody levels in tears or as immunoglobulin producing cells within the tissue. No local immunity has been demonstrated in the orbit. (2) The other type of immune response found in the eyelids, the lacrimal gland and the orbit is the involvement of these tissues in systemic diseases. Systemic diseases with an immunological basis, which affect the above mentioned tissues are: atopic diseases of the skin, autoimmune diseases, immunodeficiency diseases and lymphoproliferative diseases. (3) Finally, it is possible that the extraocular muscles and the lacrimal gland have tissue specific antigens and therefore may be target tissues for organ specific autoimmune processes.

Clinical correlations of antibodies that bind, block, or modulate human acetylcholine receptors in myasthenia gravis

Acetylcholine receptor (AChR) binding and AChR modulating antibodies were found with approximately the same frequency (86%) in 349 patients with myasthenia gravis (MG). However, the total yield of positive serological results was significantly improved (90%) by assaying AChR modulating antibodies when AChR binding antibodies were not detected, because in 27 patients (8%) only one of the two tests was positive. The immunoprecipitation test for AChR blocking antibodies yielded fewer positive results (52%), but there was a significant correlation between the degree of AChR blockade and generalization of muscle weakness. In no patient was this the only positive test, because the test for AChR modulating antibodies in this study detected both AChR blocking and modulating antibodies. Human muscle AChR was used as antigen in all tests. False positive results were rare and were attributed to unexplained antibodies to 125I-alpha-Bgt (AChR binding antibody assay) and recent general anesthesia using muscle relaxants (AChR blocking and AChR modulating antibody assays). Unexplained positive results, documented previously in 5% of patients with the Lambert-Eaton myasthenic syndrome and amyotrophic lateral sclerosis (ALS), were found in this study in two of 22 patients with ALS, but in none of 427 patients with miscellaneous neurological diseases. Patients with severe generalized MG and/or thymoma tended to have higher titers of AChR binding antibodies and greater AChR modulating antibody activity. However, some patients with severe muscle weakness had low titers of antibodies, and some patients in remission or with only ocular manifestations had high titers. These seemingly paradoxical results reflect heterogeneity in the specificities, affinities, and isotypes of anti-AChR antibodies. To effect pathogenicity, antibodies must have access in vivo to extracellular antigenic sites on the AChR. One would anticipate that antibodies with greatest pathophysiological potential would be of an IgG with greatest pathophysiological potential would be of an IgG subclass that activates complement, or of a specificity that competes for acetylcholine's binding site on the receptor or readily cross-links two AChR molecules to trigger receptor modulation (e.g., by binding to sites on the duplicated alpha-subunit). In patients with suspected MG who lack serological evidence of anti-AChR antibodies, motor endplate biopsy is required for microelectrophysiological, immunochemical, and ultrastructural studies to establish with certainty whether or not the condition is acquired MG.

Saccadic eye movements in myasthenia gravis

The peak velocities of horizontal saccades were measured in patients with myasthenia gravis (MG) to determine whether they can differentiate MG from other causes of ophthalmoplegia. Eye movements were recorded with electrooculography (EOG) or infrared scleral reflection (IR) in 42 patients with MG, 26 patients with sixth cranial nerve palsy (CNP), 19 patients with chronic progressive external ophthalmoplegia (PEO) and 28 normal subjects. Despite limitation of ductions in MG, the group means of velocities of 10 deg saccades recorded with IR were similar in MG and normal subjects. With EOG, small but statistically significant decreases in mean velocities of 10, 20 and 30 deg saccades were found in MG, compared to those in normal subjects. Twenty-one to 28% of MG patients had velocities outside of the normal range (outliers). In contrast, the group means in CNP and PEO were markedly lower than those in MG and normal subjects. The frequencies of outliers were 89 to 100% in CNP and 88 to 100% in PEO. Measurement of saccadic velocities can be helpful in differentiating MG from other causes of ophthalmoplegia.

Heterogeneity in myasthenia gravis: HLA phenotypes and autoantibody responses in ocular and generalized types

HLA phenotypes and autoantibody responses were studied in 71 Japanese patients with myasthenia gravis. HLA-A2, Bw61, and DRw9 were associated with ocular myasthenia gravis (corrected p [CP] less than 0.05 relative risk [RR] = 2.88; CP less than 0.02, RR = 3.60; and CP less than 0.001, RR = 4.63, respectively) and HLA-DRw8 was associated with generalized myasthenia gravis (CP less than 0.001, RR = 5.40). Neither HLA-B8 nor DR3 was found in Japanese patients. The titer of antiacetylcholine receptor antibody (AChR Ab) and the incidence of autoantibodies other than AChR Ab were higher in patients with generalized myasthenia gravis than in those with the ocular type (2.77 +/- 0.62 versus 0.17 +/- 0.03 pmol/ml, p less than 0.001; and 60.6 versus 29.0%, p less than 0.02, respectively). Patients with a high titer of AChR Ab or with autoantibodies had an increased frequency of HLA-DRw8 (CP less than 0.02, RR = 4.61, and CP less than 0.005, RR = 4.53, respectively); whereas patients with a low titer of AChR Ab or without autoantibodies had an increased frequency of HLA-DRw9 (CP less than 0.001, RR = 8.26, and CP less than 0.005, RR = 4.08, respectively). These findings suggest that ocular and generalized myasthenia gravis might have different immunogenetic backgrounds.

HLA antigens and acetylcholine receptor antibody in the subclassification of myasthenia gravis in Hong Kong Chinese

Thirty seven Chinese adults and 23 children in Hong Kong with myasthenia gravis were tested for HLA-A and -B antigens and acetylcholine receptor (AChR) antibody. HLA BW46 had a significantly increased prevalence in patients with juvenile onset ocular myasthenia gravis. Only one third of the juvenile ocular patients had AChR antibodies and the titres were generally low. In the adult patients taken as a whole there was a non-significant increase in the prevalence of HLA B5 and HLA B15. HLA BW46 was more prevalent in adult patients without AChR antibody and less prevalent in patients with AChR antibody but the findings were not statistically significant. It is suggested that ocular myasthenia gravis is determined by a pathological mechanism for which susceptibility is determined by HLA BW46. There was a strong correlation between ocular myasthenia gravis and Graves' disease in the adult patients. The possibility that ocular myasthenia gravis is accentuated by a BW46-associated predisposition to ocular Graves' disease is considered.

Myasthenia gravis and HLA antigens in American blacks and other races

The association of HLA B8 and DR3 with generalised adult onset myasthenia gravis (GMG) in European Caucasoids is now well established. Studies of the HLA association with myasthenia gravis (MG) in other races might help to determine the location of a critical disease locus. Some previous studies in Japanese, Thais, Asian Indians and Filipinos have been reported. In this study HLA A, B, C and DR typing on 28 American blacks with either GMG or ocular myasthenia gravis (OMG) is reported. A significant increase in both HLA A1 and B8 was detected but there was an increase in DR5 rather than DR3. A review of the HLA antigen frequencies in other races and in D-penicillamine (D-Pen) induced MG suggests that prior claims implicating immune response genes marked by DR3 require review. It seems unlikely that any particular HLA allele is involved directly. Other possibly relevant combinations of alleles or supratypes are suggested. These may provide the basis for future studies of the immunogenetic basis for MG.

Myasthenia gravis in Chinese children

A clinical study of 50 Southern Chinese myasthenic children observed for periods of two to 18 years (six years on average) revealed manifestations different from those of caucasian patients. Onset was early, at an average of 4.8 years. 82 per cent had ocular myasthenia. Ophthalmoplegia followed ptosis between three months and 10 years later. Additional facial and isolated limb-muscle fatigability developed in only 6 per cent within three months to 3 1/2 years. Only 12 per cent developed generalized myasthenia. Although extension from ocular to the generalized form did not occur later than 20 months after onset, a deterioration in ocular symptoms, without extension into generalized myasthenia, occurred in nine of 18 children during adolescence. Ptosis and generalized myasthenia responded better to anticholinesterase and/or prednisone. Ophthalmoplegia was difficult to treat. The natural clinical course was benign. Spontaneous remission occurred in 62 per cent of cases, but 54.8 per cent of these relapsed, all confined to ocular muscles. Although there was no familial occurrence of myasthenia gravis, an association was found between myasthenia and thyroid disorders in some patients and their relatives. The association with HLA BW46 antigen was striking. Acetylcholine receptor antibodies were absent in the majority, but mildly elevated titres were found in three of five patients whose ocular symptoms deteriorated during adolescence, without extension into generalized myasthenia.

Strong association of HLA BW46 with juvenile onset myasthenia gravis in Hong Kong Chinese

The HLA antigen distribution and thyroid autoantibody status of 27 Chinese children in Hong Kong with juvenile onset myasthenia gravis have been compared with 110 healthy university students from the same population. Twenty-four of the patients had ocular myasthenia. There was a significantly increased prevalence of HLA BW46 in the patients compared with controls (67% vs 26.4%, p less than 0.005) indicating that BW46 confers a relative risk of 5.6 for juvenile onset myasthenia gravis in Chinese children. The increased prevalence of BW46 was not associated with thyroid autoimmunity in the patients although the antigen is known to be associated with thyrotoxicosis in Chinese. The possibility that BW46 confers protection against the development of acetyl-choline receptor antibodies in Chinese patients is discussed. One patient had the Caucasian antigen B8 and the question whether defective immune response genes were introduced into the Chinese through Caucasian admixture is raised.

Myasthenia gravis: overlap with 'polyendocrine' autoimmunity

81 patients with spontaneously acquired myasthenia gravis (MG) were investigated for the presence of autoimmune (AI) diseases and their sera were tested for a range of organ-specific autoantibodies. 77 of the patients were HLA-phenotyped. Antibody titres to acetylcholine receptors (AChR) were higher in non-thymomatous patients who possessed HLA-B8 (p less than 0.05) and/or -DR3 (p less than 0.05) as compared to patients lacking these HLA antigens. 3 out of 20 (15%) patients with ocular MG, 7/23 (30%) with generalized MG of early onset, 11/23 (48%) generalized MG of late onset and 5/14 (35%) patients with thymoma had either overt AI diseases or significant titres of organ-specific autoantibodies suggesting subclinical AI disease. In ocular MG, low titres and an infrequent finding of antibodies to AChR (32%) as well as the low prevalence of associated autoantibodies and AI diseases indicate that this subgroup of MG consists of patients with restricted AI reactivity. HLA-B8 and -DR3 were present in all the patients with associated AI disorders in the young onset group but in none of the patients with old age of onset. In the young group, 6 out of 7 patients with associated AI conditions were women whereas the sex ratio was about equal in the older cases in both, patients with and without associated AI diseases or autoantibodies. We conclude from these observations that ageing provides conditions that allow the breakdown of self tolerance. The simultaneous presence of HLA B8, DR3 and female sex provide important additional factors for early expression of MG.

Reduction of miniature end-plate potential amplitude in extraocular and limb muscles in an animal model of myasthenia gravis

Miniature end-plate potential (MEPP) amplitudes of the superior oblique extraocular muscle (EOM) and forelimb flexor digitorum longus muscle (FDL) of rats with experimental autoimmune myasthenia gravis (EAMG) were expressed as reductions from mean MEPP amplitudes of the respective muscles of pair-matched control animals. Postjunctional blockade of neuromuscular transmission at EOM end-plates was no greater than at limb muscle end-plates. In contrast, the amount of reduction measured in EAMG-affected FDLs (52.3%) was marginally, but significantly, greater than that in EOMs (38.3%). A weak correlation was present between the MEPP reduction observed in an animal's FDL and that recorded in its EOM.

Anti-acetylcholine receptor antibodies in myasthenia gravis. Part 1. Relation to clinical parameters in 250 patients

We examined the significance of the presence or absence of anti-acetylcholine receptor (anti-AChR) antibodies in 250 myasthenia gravis (MG) patients and the relation between clinical features and anti-AChR levels. We found high anti-AChR levels in 2 out of 11 thymoma patients without MG, while 37 out of 250 MG patients had no detectable anti-AChR. The absence of these antibodies was related to purely ocular disease and to steroid therapy and/or thymectomy. Differences in anti-AChR levels did not correspond significantly to differences in disease activity when single measurements in patients were analysed. However, the results were influenced by both the presence or absence of a thymoma, the age at onset of disease and by steroid therapy. The thymic pathology and age at onset seemed to act independently. Early onset of disease was associated with high anti-AChR levels and absence of antibodies to striated muscle (anti-SM), whereas late onset was associated with low anti-AChR and the presence of anti-SM. Thymomas both have high anti-AChR and high anti-SM. The effect of steroid therapy on antibody levels was seen in all patient groups but was strongest in thymoma patients with early onset of disease.

The diagnostic significance of autoantibodies to the acetylcholine receptor

The predictive value of the assay for antibodies to the acetylcholine receptor (anti-AChR) is dependent upon the reference range used and the question being asked by the clinician. A reference range has been established after assaying sera from 200 healthy individuals, 314 patients with diseases often considered in the differential diagnosis of myasthenia gravis (MG) or found in association with MG, and 72 patients with active adult onset MG. If the assay is to be used to screen an unselected population for MG a conservative cut off point (2 units) should be used. After establishment of a differential diagnosis more significant may be attributed to a lower result (1 unit or greater). A negative result does not exclude MG. In patients with Systemic Lupus Erythematosus. Graves' disease or thymoma anti-AChR has been demonstrated in the absence of signs of MG. Such patients may have latent or subclinical MG. Two such patients subsequently developed clinically evident MG concomitant with a rise in anti AChR titre above their particular 'biological threshold'.