Molecular genetic studies of major histocompatibility complex genes in children with juvenile dermatomyositis: increased risk associated with HLA-DQA1 *0501.

Juvenile dermatomyositis (JDMS) is an inflammatory disease associated with HLA-DR3. We therefore undertook molecular genetic studies of HLA region genes to determine whether HLA-DR3 itself confers susceptibility to JDMS or whether susceptibility is conferred by alleles in linkage disequilibrium with HLA-DR3. Our results indicate that JDMS is associated with the HLA-DQA1 allele DQA1 *0501 on non-DR3 haplotypes in Caucasian JDMS. Furthermore, the reported of association between the C4A gene deletion and JDMS is likely due to linkage disequilibrium with HLA-DR3.