To investigate possible associations of GM and KM markers in European Americans (EA) and African Americans (AA) with adult and juvenile forms of the idiopathic inflammatory myopathies (IIM).
We performed serologic analyses of polymorphic determinants associated with immunoglobulin gamma heavy (GM) and kappa light chains (KM) in large populations of EA (n=514: 297 adults and 217 juveniles) and AA IIM patients (n=109: 73 adults and 50 juveniles) representing the major clinicopathologic and autoantibody groups.
For EA dermatomyositis (DM) patients, the GM 3 23 5,13 phenotype was a risk factor for both adults (OR=2.2; Pc=0.020) and juveniles (OR=2.2; Pc=0.0013). Of interest, the GM 13 allotype was a risk factor for juvenile DM (JDM) for both EA (OR=3.9; Pc<0.0001) and AA (OR=4.8; Pc=0.033). However, the GM 1,3,17 5,13,21 phenotype was a risk factor for JDM in EA but not in AA. Among the IIM autoantibody groups, GM 3 23 5,13 was a risk factor for EA adults with anti-Jo-1 autoantibodies (OR=3.4; Pc=0.0031), while the GM 3 allotype was protective for adults with anti-threonyl tRNA synthetase or anti-RNP autoantibodies (OR=0.1; Pc=0.047 and OR=0.2; Pc=0.034, respectively). In contrast, GM 6 was a risk factor for AA adults with anti-SRP autoantibodies (OR=7.5; Pc=0.041).
These data suggest that polymorphic alleles of GM and KM loci are differentially associated with IIM subgroups defined by age, ethnicity, clinical features and autoantibodies, and expand the list of immune response genes possibly important in the pathogenesis of myositis.