HLA class II allele analysis in MuSK-positive myasthenia gravis suggests a role for DQ5

Abstract

Myasthenia gravis (MG) is caused by autoantibodies targeting, in most cases, the acetylcholine receptor (AChR-MG). Different disease subtypes are distinguished on the basis of clinical characteristics and thymus pathology. In 40% of patients with anti-AChR negative generalized MG, the disease appears to be mediated by antibodies against the muscle specific kinase (MuSK-MG).1 We evaluated HLA-DRB1*, DQA1*, and DQB1* allele profile in MuSK-MG in comparison with a control population and non-thymoma early onset AChR-MG (AChR-EOMG). We chose to compare these two clinical entities as they share a high prevalence in women and a proportion of MuSK-MG patients have early onset disease. ### Patients. Our study includes consecutive unrelated patients, all with generalized MG. Patients gave informed consent to inclusion in the study, which was approved by the local Ethics Committee. The MuSK-MG group included 37 patients (8 men/29 women, onset age: 6–62 years), the thymus was normal for age in 10 patients who underwent thymectomy, thyroid autoimmunity was associated in 4/37 cases (10.5%). The AChR-EOMG group comprised 28 patients (4 men/24 women, onset age: 9–39 years), thymic hyperplasia was found in 24/26 thymectomized cases, and different autoimmune disorders were associated in 8/28 (28.6%). All patients were from Central Italy, with Italian ancestors. For …