High frequency of DQB 1*05 and absolute absence of DRB 1*13 in muscle‐specific tyrosine kinase positive myasthenia gravis

Background and purpose Myasthenia gravis ( MG ) is an autoimmune disease but certain genetic factors predispose its development. Since susceptibility to different forms of MG is linked to a number of allelic variants, the aim of this study was to explore the human leukocyte antigen ( HLA ) profile of our patients with muscle‐specific tyrosine kinase (Mu SK ) MG . Methods Human leukocyte antigen ( HLA ) typing was performed in our cohort of 31 Mu SK MG patients available for the study. The allele groups of DRB 1* and DQB 1* loci were typed with sequence‐specific oligonucleotide probes and high resolution typing for DQB 1* was performed using sequence‐specific primers. HLA frequencies were compared with unrelated healthy bone marrow donors. Results Significant association of Mu SK MG with alleles DRB 1*14 [odds ratio ( OR ) 3.8], DRB 1*16 ( OR 3.3) ( P  < 0.01) and DQB 1*05 ( OR 2.2) ( P  < 0.05) was found. In our patients the most frequent DQB 1* allele was DQB 1*05:02. An absolute absence of DRB 1*13 in our cohort of Mu SK MG patients was also found, whilst this allele was present in 25% (495/1992) of control subjects ( OR 0) ( P  < 0.01). The HLA DRB 1*16− DQB 1*05 ( OR 2.9) haplotype was found to be associated with Mu SK MG ( P  < 0.05). Conclusions The strong association of Mu SK MG with DQB 1*05 alleles observed in patient series from other countries was confirmed. The novel finding in our cohort of Mu SK MG patients was the absolute absence of DRB 1*13 allele, which might have a protective role in the development of Mu SK MG , at least in our population.