Sporadic inclusion body myositis: HLA-DRB1 allele interactions influence disease risk and clinical phenotype

Mastaglia, F.L., Needham, M., Scott, A., James, I., Zilko, P., Day, T., Kiers, L., Corbett, A., Witt, C.S., Allcock, R., Laing, N., Garlepp, M. and Christiansen, F.T. (2009) Sporadic inclusion body myositis: HLA-DRB1 allele interactions influence disease risk and clinical phenotype. Neuromuscular Disorders, 19 (11). pp. 763-765.

Abstract

Susceptibility to sIBM is strongly associated with the HLA-DRB1*03 allele and the 8.1 MHC ancestral haplotype (HLA-A1, B8, DRB1*03) but little is known about the effects of allelic interactions at the DRB1 locus or disease-modifying effects of HLA alleles. HLA-A, B and DRB1 genotyping was performed in 80 Australian sIBM cases and the frequencies of different alleles and allele combinations were compared with those in a group of 190 healthy controls. Genotype-phenotype correlations were also investigated. Amongst carriers of the HLA-DRB1*03 allele, DRB1*03/*01 heterozygotes were over-represented in the sIBM group (p < 0.003) while. DRB1*03/*04 heterozygotes were under-represented (p < 0.008). The mean age-at-onset (AAO) was 6.5 years earlier in DRB1*03/*01 heterozygotes who also had more severe quadriceps muscle weakness than the rest of the cohort. The findings indicate that interactions between the HLA-DRB1*03 allele and other alleles at the DRB1 locus can influence disease susceptibility and the clinical phenotype in sIBM.