High frequency of DQB1*05 and absolute absence of DRB1*13 in muscle-specific tyrosine kinase positive myasthenia gravis.

OBJECTIVE

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 (MuSK) MG.

METHODS

Human leukocyte antigen (HLA) typing was performed in our cohort of 31 MuSK MG patients available for the study. The allele groups of DRB1* and DQB1* loci were typed with sequence-specific oligonucleotide probes and high resolution typing for DQB1* was performed using sequence-specific primers. HLA frequencies were compared with unrelated healthy bone marrow donors.

RESULTS

Significant association of MuSK MG with alleles DRB1*14 [odds ratio (OR) 3.8], DRB1*16 (OR 3.3) (P < 0.01) and DQB1*05 (OR 2.2) (P < 0.05) was found. In our patients the most frequent DQB1* allele was DQB1*05:02. An absolute absence of DRB1*13 in our cohort of MuSK MG patients was also found, whilst this allele was present in 25% (495/1992) of control subjects (OR 0) (P < 0.01). The HLA DRB1*16-DQB1*05 (OR 2.9) haplotype was found to be associated with MuSK MG (P < 0.05).

CONCLUSIONS

The strong association of MuSK MG with DQB1*05 alleles observed in patient series from other countries was confirmed. The novel finding in our cohort of MuSK MG patients was the absolute absence of DRB1*13 allele, which might have a protective role in the development of MuSK MG, at least in our population.