Heterogeneous immunogenetic background in Japanese adults with myasthenia gravis

Two-step nationwide epidemiological survey of myasthenia gravis in Japan 2018

Objective

To study the updated prevalence and clinical features of myasthenia gravis (MG) in Japan during 2017.

Methods

We sent survey sheets to the randomly selected medical departments (number = 7,545). First, we asked the number of MG patients who visited medical departments from January 1, 2017, to December 31, 2017. Then, we sent the second survey sheet to the medical departments that answered the first survey to obtain the clinical information of patients who received MG diagnosis between January 1, 2015, and December 31, 2017.

Results

The received answer to the first survey were 2,708 (recovery rate: 35.9%). After all, the prevalence of the 100,000 population was estimated as 23.1 (95%CI: 20.5–25.6). As a result of the second survey, we obtained 1,464 case records. After checking the duplications and lacking data, we utilized 1,195 data for further analysis. The median [interquartile range (IQR)] from the onset age of total patients was 59 (43–70) years old. The male-female ratio was 1: 1.15. The onset age [median (IQR)] for female patients was 58 (40–72) years old, and that for male patients was 60 (49–69) years old (Wilcoxon-Mann-Whitney test, p = 0.0299). We divided patients into four categories: 1) anti-acetylcholine receptor antibody (AChRAb) (+) thymoma (Tm) (-), 2) AChRAb(+)Tm(+), 3) anti-muscle-specific kinase antibody (MuSKAb) (+), and AChRAb(-)MuSKAb(-) (double negative; DN). The onset age [median (IQR)] of AChRAb(+)Tm(-) was 64 (48–73) years old, and AChRb(+)Tm(+) was 55 (45–66), MuSKAb(+) was 49 (36–64), DN was 47 (35–60) year old. The multivariate logistic regression analysis using sex, initial symptoms, repetitive nerve stimulation test (RNST), and edrophonium test revealed that sex, ocular symptoms, bulbar symptoms, and RNST were factors to distinguish each category. The myasthenia gravis activities of daily living profile at the severest state were significantly higher in MuSKAb(+). MuSKAb(+) frequently received prednisolone, tacrolimus plasmapheresis, and intravenous immunoglobulin; however, they received less acetylcholine esterase inhibitor. 99.2% of AChRAb(+)Tm(+) and 15.4% of AChRAb(+)Tm(-) received thymectomy. MuSKAb(+) did not receive thymectomy, and only 5.7% of DN received thymectomy. The prognosis was favorable in all categories.

Conclusion

Our result revealed that the prevalence of Japanese MG doubled from the previous study using the same survey method in 2006. We also found that the onset age shifted to the elderly, and the male-female ratio reached almost even. Classification in four categories; AChRAb(+)Tm(-), AChRAb(+)Tm(+), MuSKAb(+), and DN, well describe the specific clinical features of each category and differences in therapeutic approaches.

Whole-exome sequencing and human leukocyte antigen analysis in familial myasthenia gravis with thymoma: Case report and literature review

Myasthenia gravis (MG) is an autoimmune disease characterized by impaired neurotransmission at the neuromuscular junction. MG is generally non-inherited but is rarely inherited. Here, we report two patients with MG in the same pedigree: a 62-year-old Japanese man and his 46-year-old daughter who were positive for anti-acetylcholine receptor antibodies and had thymoma. We performed whole-exome sequencing (WES) and human leukocyte antigen (HLA) analyses to investigate the genetic contribution to familial onset. WES analysis of both patients showed no known variations in candidate genes for familial MG, and HLA analysis failed to detect HLA haplotypes seen in early-onset and late-onset MG. These findings suggest the presence of an unknown genetic background. Previous genetic studies on familial MG have identified ENOX1 and IFNGR1 as candidate genes in patients without thymoma, whereas no studies have identified candidate genes in patients with thymoma. To explore causative genes, it may be necessary to consider whether the genetic background differs between patients with and without thymoma in familial autoimmune MG.

Association between HLA-DRB1 and myasthenia gravis in a northern Han Chinese population

The cause of myasthenia gravis (MG) is unknown, but it is widely believed to be an autoimmune disease occurring in genetically susceptible individuals. The human leukocyte antigen (HLA) region is considered to be the most important genetic region for MG susceptibility genes. To investigate the association between HLA-DRB1 and myasthenia gravis (MG) in a northern Han Chinese population, a polymerase chain reaction with sequence-specific oligonucleotide probe hybridization method was used to determine the HLA-DRB1 genotypes of 91 patients with MG and 171 healthy individuals. We found that the HLA-DRB1(*)09 allele was significantly more prevalent among patients with MG than among healthy controls, especially those who experienced early onset of the disease (≤40 years), those who were seronegative for acetylcholine receptor antibody, and those with ocular MG. The prevalence of the HLA-DRB1(*)08 allele was significantly lower among patients with MG than among controls. These results indicate that HLA-DRB1(*)09 might be positively associated and DRB1(*)08 negatively associated with MG in the northern Han Chinese population.

HLA class I and class II polymorphisms in Saudi patients with myasthenia gravis

Myasthenia gravis (MG) is a rare autoimmune disease of the neuromuscular junction. MG has been shown to be associated with many HLA antigens in different populations. Here we have analysed the frequency of HLA-A, B, DR and DQ in a group of Saudi MG patients and compared their results to a group of healthy controls. MG in Saudi patients is found to be associated with HLA-A*23, B*08, B*18, DRB1*16 and DRB1*13. The strongest association was with HLA-B*08, which was associated with young age at onset and female gender. Our results are in line with other published results from around the world and warrant fine mapping of the area using microsatellite to map the disease gene.

Subtle differences in HLA DQ haplotype-associated presentation of AChR α-chain peptides may suffice to mediate myasthenia gravis

The HLA DQA1 and DQB1 alleles were determined on a set of 24 myasthenia gravis patients that had previously been examined for their T-cell proliferative responses to the 18 overlapping peptides representing the extracellular domain of hAChR alpha-chain. Patient responses according to assumed cis or trans haplotypes were significantly higher in most cases relative to normal controls. Comparisons of in vitro peptide-stimulated T-cell responses of patient pairs which had DQA1:DQB1 in common displayed responses in tighter distribution relative to comparisons in which patient pairs did not share the same DQA1:DQB1 haplotype. Similar haplotypes, such as DQA1*0102:DQB1*0602 and DQA1*0102:DQB1*0604, tended to exhibit similar responses and were grouped according to this similarity. Modified F-test and Student's T-test analyses on DQ isoform bearing groups revealed that high responses to peptide alpha34-49 were associated with A1*0102:B1*0602/0604, A1*0301:B1*0302 and A1*0401/0303:B1*0301. Peptide alpha146-162 showed higher responses in A1*0301:B1*0302 group and moderate responses in A1*0401/0303:B1*0301 groups. Differences in the age of disease onset relative to DQ haplotypes were also observed. Groups of A1*0301:B1*0302, A1*0501:B1*0201 and A1*0102:B1*0604 showed earlier ages of disease onset relative to those of A1*0102:B1*0602 or A1*0505:B1*0301.

Suppression by mAbs against DQB1 peptides ofin vitroproliferation of AChR-specific T cells from myasthenia gravis patients

It has been indicated that multiple genes, including HLA genes, are collectively involved in the susceptibility to myasthenia gravis (MG). DQB1 alleles represent one of those associated with MG. We have prepared B-cell hybridomas that produce mAbs against peptides corresponding to the tip of the MHC antigen-binding cavity (region 70-90) of alleles DQB1*02, *03, *05 and *06. The mAbs bound to DQ molecules isolated from cells. In the assays using peripheral blood lymphocytes (PBL) from patients with MG, the mAbs against peptides of the correlate HLA DQ sequences inhibited the in vitro proliferation of acetylcholine receptor (AChR)-specific T cells. The results indicate that the function of disease-related MHC alleles may be blocked by directly and selectively targeting the antigen-presenting region on these MHC molecules. The results also suggest that DQ molecules are one of those involved in the restriction of autoimmune anti-AChR responses in MG. The strategy could provide an effective means for immunointervention in MG. It may also potentially be adapted for down-regulation of undesirable immune responses such as in other autoimmune diseases, allergic reactions, or clinical conditions where immune responses to a therapeutic protein develop.

Myasthenia gravis accompanied by alopecia areata: clinical and immunogenetic aspects

The purpose of this study was to evaluate the clinical characteristics of patients who had both myasthenia gravis (MG) and alopecia areata (AA). Clinical information was retrospectively collected for 159 Japanese patients with MG. Human leukocyte antigen (HLA)-DQB1 and DRB1 alleles were determined by genotyping. Of 159 MG patients, six (3.7%) developed AA after the onset of MG and thymectomy. The prevalence of AA in MG patients was higher than that reported in Caucasians. The frequencies of bulbar involvement, myasthenic crisis, and thymoma were significantly higher in MG patients with AA than in those without (P = 0.007, 0.004, and 0.006, respectively). All but one patient with AA had advanced stage thymoma. Three patients with a severe form of AA (alopecia totalis) had additional autoimmune diseases: myocarditis, myositis, and pure red cell aplasia. DRB1*0901 and DQB1*0303 tended to be more frequently detected in the six MG patients with AA than in the 82 patients without it. In conclusion, a subset of MG patients who have severe neuromuscular symptoms and thymoma develop AA several years after thymectomy.

HLA genotypes in turkish patients with myasthenia gravis: Comparison with multiple sclerosis patients on the basis of clinical subtypes and demographic features

The nature and intensity of the association of myasthenia gravis (MG) with distinct human leukocyte antigens (HLA) haplotypes differ between ethnic populations. The aims of the present study were to examine the relationship between HLA class I and II haplotypes and MG; to show the HLA associations with various MG subsets; and to investigate the association between MG and clinical subgroups of multiple sclerosis (MS) regarding HLA haplotypes. A total of 66 patients with MG were enrolled onto the study. The mean age at onset was 42.01 years. A total of 122 clinically definite MS patients and 188 healthy subjects were examined as control groups. The present study clearly showed associations with HLA-DR3, -B8, -A1, and -A2 in MG. In patients with early-onset MG, associations with HLA-DR3, -B8, and -A2 were stronger. When compared with MS, in the MG group, there was still a strong association with -B8, -DR3, and -A1. In subgroup analysis, there was no difference between MG and primary progressive MS patients. On the basis of the presence of anti-AChR antibodies, there was a statistically significant association with HLA-DR3. On the basis of presence of thymoma, no HLA allele showed clear associations in MG patients with thymoma. This is the first study to examine the relationship between HLA haplotypes and MG in the Turkish population and to compare MG with another autoimmune disease, MS, on the basis of the HLA haplotypes. Further investigations with a larger population are required to explain this finding.

Initial predictors of development of pure red cell aplasia in myasthenia gravis after thymectomy

Pure red cell aplasia (PRCA) is well known to be concomitant with myasthenia gravis (MG), but it is difficult to predict the development of PRCA in patients with MG. Of 135 patients with MG, four (2.9%) had PRCA. All patients developed PRCA after thymectomy during a period when MG was in remission. The frequencies of thymoma, bulbar involvement and high anti-acetylcholine receptor (AChR) antibody levels were significantly higher in four patients with PRCA. Japanese MG patients with these characteristics at presentation were at significant risk for the development of PRCA after thymectomy.

Autoreactive T cells to the P3A+ isoform of AChR alpha subunit in myasthenia gravis

In vitro T cell proliferative response to an alternative splicing variant of acetylcholine receptor alpha subunit (AChR alpha) with the P3A exon-encoded region was examined in peripheral blood samples from 28 myasthenia gravis (MG) patients and 14 healthy donors using recombinant fragments and synthetic peptides. T cells responsive to the P3A region-specific sequences were detected in five MG patients, all of whom were late-onset disease with thymoma, but in none of healthy donors. These autoreactive T cells may be involved in the pathogenic process in a subset of MG patients.