HLA Class I and II Alleles in Anti-Acetylcholine Receptor Antibodies Positive and Double-Seronegative Myasthenia Gravis Patients of Romanian Descent

<b>Background</b>: Several significant associations between certain Human Leukocyte Antigen (HLA) alleles and myasthenia gravis (MG) subtypes were established in populations from Western Europe and North America and, to a lesser extent, from China and Japan. However, such data are scarcely available for Eastern Europe. This study aimed to analyze the associations of HLA Class I and II alleles with MG and its serological subtypes (with anti-acetylcholine receptor autoantibodies, RAch+MG, and double-seronegative, dSNMG) in myasthenic patients of Romanian descent. <b>Methods:</b> We consecutively enrolled adult Romanian unrelated myasthenic patients, which were genotyped by next-generation sequencing for HLA-A, -B, -C, -DRB1 and -DQB1. The descent-matched controls were represented by two separate groups of random normal subjects genotyped for the main five HLA loci at the two-digit and four-digit levels, respectively, collected from the Allele Frequency Net Database. <b>Results:</b> A total of 40 patients (females: 80.00%; median age at onset: 42.5 years, range: 1-78; RAch+MG: 75.00%; dSNMG: 22.50%) were included. We were able to confirm previously acknowledged allelic associations: positive for HLA-B*08, DRB1*14:54 and DRB1*16:01 and negative for DRB1*13. However, we found some potential novel significant positive associations between MG and the HLA-A*02:36, B*47, B*73, B*44:27 and B*57:02 alleles. All alleles positively associated with MG remained significantly associated with RAch+MG, regardless of the patients' clinical and thymic heterogeneity. We found significant positive associations between dSNMG and the HLA-B*47, B*44:27 and DRB1*14:54 alleles that are shared with RAch+MG. <b>Conclusions:</b> These results suggest both distinct and common etiopathogenic mechanisms between dSNMG and RAch+MG. Our study pioneers allele associations in Romanian MG patients.