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

HLA typing using next-generation sequencing for Chinese juvenile- and adult-onset myasthenia gravis patients

To compare HLA typing between juvenile- and adult-onset myasthenia gravis (MG), we enrolled 101 children (age ≤12 years) and 168 adults (age ≥20 years) with MG. We excluded patients with histories of thymoma, thyroid disease, or other autoimmune disease. We selected 41 seronegative juvenile-onset patients with ocular symptoms only, and 41 seropositive adult-onset patients with generalized symptoms. We used next-generation sequencing for typing and analysis of HLA genes (Loci: A, B, C, DPA1, DPB1, DQA1, DQB1 and DRB1). Haplotypes HLA-A∗02:07:01-B∗46:01:01-C∗01:02:01-DQA1∗01:01:01-DQB1∗03:03:02-DRB1∗09:01:02, HLA-A∗11:01:01, HLA-A∗24:02:01, and HLA-DPA1∗02:02:02 were found to be related to juvenile-onset MG and HLA-A∗01:01:01, HLA-A∗02:03:01, HLA-C∗03:04:01, and HLA-DQB1∗06:02:01 to adult-onset MG. Therefore, our findings suggested that HLA typing might determine the heterogeneity between AChR-Ab negative juvenile-onset and AChR-Ab positive adult-onset Chinese MG patients.

Nonthymoma early-onset- and late-onset-generalized myasthenia gravis—A retrospective hospital-based study

OBJECTIVE

Acquired myasthenia gravis (MG) is predominantly due to nicotinic acetylcholine receptor (AChR) autoantibodies (Ab). Differences between nonthymoma early-onset and late-onset MG were reported. We studied the clinical and serological characteristics of nonthymoma AChR Ab-positive-generalized MG patients.

PATIENTS AND METHODS

Chinese AChR Ab-positive-generalized MG patients who had generalized disease for 3 years or longer were studied.

RESULTS

Among 41 such patients, 25 (61%) were female. The mean onset age was 43.5 years (range 9-78 years) and the mean follow-up duration was 7.8 years (range 3-20 years). Sixteen (39%) patients had late-onset disease (onset age >or=50 years). Compared to early-onset patients (onset age <50 years), late-onset patients were characterized by male predominance (p=0.002), absence of thymic lymphofollicular hyperplasia (p=0.036), and a higher striated muscle Ab seropositivity rate (94% versus 4%, p<0.001). Although there was no statistically significant difference in clinical severity and outcome or response to treatment between late-onset and early-onset patients, 50% and 75% of late-onset patients had moderate or severe disease at onset and worst status, respectively, compared to 28% and 52% for early-onset patients at onset and worst status, respectively. Also 63% of late-onset patients had disease progressed within first 3 years compared to only 40% of early-onset patients did.

CONCLUSION

Nonthymoma late-onset-generalized MG patients were common among Hong Kong Chinese, with a statistically non-significant trend that it was clinically more severe than early-onset MG but with similar clinical outcome or response to treatment; >90% of these patients were seropositive for striated muscle Ab.

Clinical and serological study of myasthenia gravis in HuBei Province, China

BACKGROUND

Ocular and childhood myasthenia gravis (MG) cases seem relatively more common in Oriental than in Caucasian populations, but there have been no comprehensive serological studies on patients from mainland China.

METHODS

391 unselected patients with MG attending Tongji Hospital in WuHan (the largest hospital in the province of HuBei, China) were studied during a 15-month period; most had already received treatment for their condition.

RESULTS

The male to female ratio was 0.8. 50% of the patients were children (<15 years), and age at onset showed a single peak at between 5 and 10 years of age. 64% of the children and 66% of the adults were positive for acetylcholine receptor (AChR) antibodies but the antibody titres were lower than in similar Caucasian studies, although this was partly due to the high incidence of ocular MG. Of the 43 patients with generalised MG without AChR antibodies, only 1 had muscle-specific kinase antibodies (2.5%) and 2 had voltage-gated calcium channel antibodies indicating probable Lambert-Eaton myasthenic syndrome. 75% of the children, compared with only 28% of the adults, had ocular MG. Thymoma was evident by MRI in 1.5% of children and in 20% of adults. Despite most patients having received prednisone, very few had obtained full clinical remission.

CONCLUSION

This study emphasises the frequency of early childhood onset with ocular symptoms and shows that many of these patients have AChR antibodies. By contrast, patients presenting in later age seem to be very uncommon in comparison with recent studies in Caucasian populations.

HLA Class II and class I polymorphism in venezuelan patients with myasthenia gravis

Oligotyping performed among ethnically mixed Venezuelan patients with myasthenia gravis (MG) and controls has revealed positive associations of HLA class I A*31, B*08, B*39, B*40, C*15, C*17, and class II DRB1*09 and negative associations of DQB1*06 and DQA1*02 with the disease. Sequential removal of human leukocyte antigen B (HLA-B) alleles when relative predispositional effects (RPEs) were looked for demonstrated that B*08 is the allele group with the largest contribution in the overall MG patients followed by B*39 and B*40. Several specificities (A*31, B*08, C*17, DRB1*03, DQA1*05, and DQB1*02) indicated increased frequencies among patients with thymic hyperplasia versus patients without hyperplasia or controls. Tests to identify alleles with the strongest association to MG in our patients detected DRB1*13 and B*38 as possible predisposing secondarily associated alleles in patients with hyperplasia. The associations observed disappear after Bonferoni correction of probability values and have been described in patients of Caucasian and/or Oriental ethnic background. Thus, our results reflect the heterogeneity of our population and of the patients tested and suggest a limited influence of several HLA genes in this heterogeneous disease or that these might be only markers of nearby non-HLA genes responsible for the susceptibility or resistance effect.

Clinical evaluation and management of myasthenia gravis

Myasthenia gravis (MG) is a syndrome of fluctuating skeletal muscle weakness that worsens with use and improves with rest. Eye, facial, oropharyngeal, axial, and limb muscles may be involved in varying combinations and degrees of severity. Its etiology is heterogeneous, divided initially between those rare congenital myasthenic syndromes, which are genetic, and the bulk of MG, which is acquired and autoimmune. The autoimmune conditions are divided in turn between those that possess measurable serum acetylcholine receptor (AChR) antibodies and a smaller group that does not. The latter group includes those MG patients who have serum antibodies to muscle-specific tyrosine kinase (MuSK). Therapeutic considerations differ for early-onset MG, late-onset MG, and MG associated with the presence of a thymoma. Most MG patients can be treated effectively, but there is still a need for more specific immunological approaches.

Myasthenia gravis with thymoma is more common in the Maori and Pacific Island populations in New Zealand

BACKGROUND

The association of myasthenia gravis (MG) with thymoma is well recognized. Our clinical impression has been that MG associated with thymoma may be more common in patients of Polynesian descent than in other races.

AIM

To determine the influence of ethnicity on the association of MG with thymoma in our population.

METHOD

Review of all cases of thymectomy performed at Greenlane Hospital in Auckland for the 20-year period from June 1978 to June 1998.

RESULTS

There were 103 thymectomies performed in the study period. Fifty-five thymomas were identified, 15 in subjects of Maori or Pacific Island ethnicity and 40 in subjects of other races, predominantly Caucasian. Ten of 15 Maori or Pacific Island subjects with thymoma had MG (67%), compared with 15 of 40 subjects of other races (37.5%, P = 0.05). The mean age of Maori or Pacific Island subjects with thymoma and MG was 42.5 years, compared with 56.3 years in subjects from other races (P = 0.06). All five Maori and Pacific Island subjects with invasive thymoma had MG, whereas only four of 15 subjects (27%) from other races with invasive tumours had MG (P < 0.01). The overall incidence of thymoma and the proportion of thymomas that were invasive did not differ between the ethnic groups.

CONCLUSIONS

Myasthenia gravis with thymoma occurs more frequently among Maori or Pacific Island people than in other racial groups in our population. This is due to an increase in the proportion of cases with thymoma who have MG in this group, while the overall frequency of cases of thymoma is similar between groups. MG with thymoma in the Maori or Pacific Island populations also presents at a younger age and is more often associated with tumour invasion.

Juvenile myasthenia: diagnosis and treatment

Myasthenia in children can be juvenile (autoimmune) or congenital. Juvenile myasthenia (JM) is an autoimmune disorder characterised by fluctuating weakness and fatigue in the ocular, facial, bulbar or limb muscles. Diagnosis is confirmed by electromyography (EMG), single fibre EMG and the patient's clinical response to anticholinesterase medication. Serology is less helpful in children because acetylcholine receptor antibodies, usually positive in adults, are frequently absent in patients with prepubertal onset of the disease. Treatment methods in JM include anticholinesterase drugs, thymectomy and immunomodulatory agents. Plasmapheresis and intravenous immunoglobulin are used in myasthenic crisis. The prognosis of patients with JM is usually good, clinical remission being achieved in the majority of patients with the current treatment methods.

A susceptibility region for myasthenia gravis extending into the HLA-class I sector telomeric to HLA-C

We have analyzed a series of HLA region markers in 207 UK Caucasoids with early-onset myasthenia gravis (EOMG, onset before age 40), where there is a strong female bias. The well known associations with HLA-DR3 and -B8 have now proved to be significantly stronger in the 165 females than in the 42 males. In patients (of either sex) lacking -DR3, there was also a significant increase in HLA-DR2. Although the muscle weakness in EOMG is clearly mediated by autoantibodies, the associations are consistently stronger with HLA-B8 (in class I) than with HLADR3 (in class II), as confirmed here. We therefore typed 87-137 cases for polymorphisms at four loci in the intervening class III region, and also at three in the adjacent stretch of class I. At each locus, one allele tended to co-occur with HLA-B8 and showed strong and highly significant associations in the patients. There appeared to be a region of maximal susceptibility extending from HSP70 (in class III) past HLA-B and HLA-C at least 600 kb telomerically into the class I region, which is now being mapped in detail. Any candidate genes here that act shortly after puberty may allow more precise localization of susceptibility.

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.

Association of HLA-Bw46DR9 combination with juvenile myasthenia gravis in Chinese

One hundred and fifty two Chinese patients with myasthenia gravis in Taiwan were investigated for HLA-A, B, C and DR/DQ typing. HLA-Bw46 and DR9 frequencies were significantly increased in patients compared with the control group, and there was a decrease in DR3. Further analysis between different subgroups of patients showed Bw46 and DR9 were more significantly increased in the juvenile group than in the adult group. No single HLA allele was associated with either clinical type or thymic pathology, but there was an excess of BW46DR9 combination in both juvenile and ocular type patients. The Chinese population with myasthenia gravis is characterised by earlier age at onset, more ocular forms and less clinically severe illness than in whites, and these characteristics indicate a special subgroup that correlates with the strong Bw46DR9 association.

Myasthenia gravis in Hong Kong Chinese. 1. Epidemiology and adult disease

A territory-wide study of myasthenia gravis (MG) was conducted in Hong Kong. Two hundred and sixty-two Chinese patients (159 adult and 103 paediatric onset) were identified, corresponding to a point prevalence and period prevalence of 53.5 and 62.2 per million respectively, and an average annual incidence of 4.0 per million population. Nine patients died, 7 from MG, giving a case fatality rate of 0.027. Female predominance was present in the whole group of patients (female to male ratio 1.6:1) and in those with adult disease (ratio 2.1:1), but not in those with onset in childhood (ration 1.1:1). Onset of disease was most common in the first 3 decades of life, and became less common in subsequent decades. Juvenile onset MG occurred in 39.3% of patients and restricted ocular MG in 47.9%. Familial occurrence was found in 5 patients. In the 159 adult onset patients, ocular disease was most common (32.7%), followed by mild generalised (29.6%), moderately severe generalised (24.5%), fulminating (11.9%) and late severe disease (1.3%). The mean age of onset of symptoms was 36.7 years. The symptomatology was similar to that of Caucasoid populations. Autoimmune thyroid disease was the commonest associated disease, and the incidence of thymoma among thymic abnormalities was high at 38%.

Myasthenia gravis in Hong Kong Chinese. 2. Paediatric disease

In a study covering 85% of the population of Hong Kong, 39% of all myasthenia gravis (MG) patients, i.e. 103 individuals (54 girls and 49 boys) were found to have had MG with onset before puberty. Two patients had transient neonatal MG, 20 had early onset juvenile MG and 81 had late onset juvenile MG. Restricted ocular MG occurred in 71% of patients and the remainder had generalised MG. The median age at onset was 4 years. Complete remission occurred in 34 patients (34%), a good response in 14 (14%), and fair response in 32 (32%). The clinical course remained static in 16 patients (16%) and 3 patients deteriorated. Two patients died, 1 with myasthenic crisis and the other with cholinergic crisis. All patients, except 2 with neonatal MG, were initially treated with anticholinesterase, but 24% also required steroid therapy. Thymectomy was performed for 12 patients, of whom 5 (42%) showed marked improvement. Thymic histology was normal in 3, showed hyperplasia in 6, non-invasive thymoma in 1 and involution in 2. The most commonly associated disease was Graves' disease which occurred in 7 patients (7%).

HLA antigens in Japanese patients with myasthenia gravis

HLA antigens in 104 Japanese patients and 41 families with myasthenia gravis (MG) were investigated. The frequencies of DR9 and DRw13 were significantly increased in the patients who developed MG before 3 yr of age. The DQw3 antigen was positive for all the patients that developed MG before 15 yr with only one exception. All the examined cases that developed MG before 3 yr (including this DQw3 negative patient) had the same DQA and DQB DNA restriction fragments. These HLA frequencies decreased as the age of onset increased, and no significant association was observed in adult-onset MG. No patients had B8, DR3, and DQw2. The relative risk was higher for the DR9/DRw13 heterozygotes (37.4) than for DR9 (16.4) or DRw13 (7.1) in the childhood-onset MG. Statistical analysis suggested that DR9 and DRw13 (or DQw1 and DQw3) act synergistically in the disease development. Family study revealed diverse DR9 haplotypes. The most frequent DRw13 haplotype was Bw44-BFF-C4A3B1-DRw13-DQw1, which may be evolutionarily related to the caucasian B8-DR3-DQw2 haplotype. These results showed that MG in early childhood in Japanese individuals is genetically different from that in adulthood and that in caucasians.

Immunoglobulin allotypes in caucasian and Chinese myasthenia gravis: differences from Japanese patients

The G2m(n) allotype was significantly increased in Chinese female and high autoantibody cases, and in caucasians with pure ocular myasthenia, or undetectable autoantibody. In contrast to the strong Glm(x) association reported in Japanese, no overall Gm haplotype, or Am or Km allotype association was found in 90 (Taiwan) Chinese and 181 caucasian myasthenia gravis patients.

Association of HLA-DRw9 with myasthenia gravis in Chinese

HLA phenotypes were studied in 59 Chinese myasthenia gravis (MG) patients. Unfractionated peripheral blood mononuclear cells were used for typing of HLA-A, B and C, and B-enriched lymphocytes for HLA-DR. Seventy-nine healthy subjects were included as controls. When compared with healthy controls, the patients showed significant increases in HLA-Bw46 (47.5% versus 14%, chi 2 = 18.7, P less than 0.001), HLA-DRw9 (59.3% versus 11%, chi 2 = 35.7, P less than 0.001), while HLA-DR3 was decreased (3.4% versus 32.9%, chi 2 = 18.2, P less than 0.001). Further analysis showed that the primary association was with DRw9 and the increase in Bw46 was secondary to it. Both HLA-Bw46 and -DRw9 were increased in all subgroups except where the age of onset was greater than 40 years. Finally, the HLA-A2-Bw46-DRw9 combination was also significantly increased in patients (25.4% versus 5.1%, chi 2 = 11.5, P less than 0.001), especially in the subgroups of MG with age of onset of less than 10 and males with age of onset of less than 40 years.

The distribution of HLA-A,B, DR antigens in Chinese myasthenia gravis

The association of HLA antigens with Myasthenia Gravis (MG) in many different races is well known. In this study, HLA-A, B and DR antigens were typed on 65 Chinese MG and 232 controls for HLA-A, B and 61 for DR antigens. A2 and DRw9 increased significantly in patients with MG (p less than 0.025 and p less than 0.05 respectively). DR2 and DR4 had the opposite influence (both p less than 0.005). Several alleles were shown to have relatively high values of P D/A and relative risk but low P A/D and E.F, which suggests the marker heterogeneity of MG. Comparisons of clinically different types of MG, variations of the age of onset and thymic pathology did not show any statistically significant difference in HLA distributions. The clinical implications were discussed.

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.

Acetylcholine receptor antibodies in the elderly and in Down's syndrome

Serum antibodies to the acetylcholine receptor (anti-AChR) have been reported in Japanese individuals who were elderly or had Down's syndrome at frequencies of 18% and 24%, respectively. We have measured serum anti-AChR in 3 Caucasoid groups: 53 elderly patients (aged 65-92 years) with miscellaneous (non-myasthenic) disorders, 30 individuals with Down's syndrome, and 40 elderly patients (aged 71-93 years) known to have strongly positive thyroid autoantibodies. A raised titre (greater than 0.2 nmol/l) was confined to 3 patients in the third group (7.5%). We conclude that an increased frequency of anti-AChR antibodies is not a feature of Caucasians who are elderly or have Down's syndrome, and that, even in an elderly group with a high titre of another autoantibody, the frequency of anti-AChR is lower than in elderly Japanese individuals.

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.