Genetic risk and protective factors for idiopathic inflammatory myopathy in Koreans and American whites: a tale of two loci.
OBJECTIVE
To better understand genetic contributions to autoimmunity, immunogenetic markers were studied in two racially discrete and geographically isolated populations of patients with idiopathic inflammatory myopathy (IIM).


METHODS
Clinical characteristics, as well as clinical and autoantibody subsets, were defined in 151 American white patients and 50 Korean patients with IIM. HLA-DRB1 and DQA1 genotyping was performed on patients and racially matched controls by standard molecular techniques. Gm allotypes and phenotypes were determined by the hemagglutination-inhibition method.


RESULTS
HLA-DRB1*0301, the linked allele DQA1*0501, and DRB1 alleles sharing the first hypervariable region motif 9EYSTS13 were major genetic risk factors for the development of myositis in whites (corrected P [Pcorr] < 0.0004, odds ratio [OR] 11.2, 4.5, and 3.1, respectively, for each factor versus controls). Although both the white and Korean patients had a similar distribution of clinical characteristics, autoantibody profiles, and clinical groups, no HLA-DRB1 nor DQA1 allele or motif was found to be a risk factor for IIM in the Korean patients. However, DRB1*14 was a protective factor in Korean patients without myositis-specific autoantibodies (Pcorr = 0.004, OR 0.046). In addition, although no Gm phenotype or allotype was identified as a risk factor in whites, Gm 21 was a protective factor for the development of IIM in Koreans (Pcorr = 0.024, OR 0.3).


CONCLUSIONS
Although myositis patients in the US and Korea share similar clinical and serologic features, the immune response genes predisposing to and protecting from myositis in each of these ethnic groups differ at two chromosomal loci. These data suggest that multiple genetic loci should be studied to identify risk and protective factors for some autoimmune diseases in various ethnic populations.
Rider
L G
LG
Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
Shamim
E
E
Okada
S
S
Pandey
J P
JP
Targoff
I N
IN
O'Hanlon
T P
TP
Kim
H A
HA
Lim
Y S
YS
Han
H
H
Song
Y W
YW
Miller
F W
FW
D000328:Adult; D003882:Dermatomyositis / Q000097:blood / Q000453:epidemiology / Q000235:genetics* / Q000517:prevention & control; D020022:Genetic Predisposition to Disease; D006683:HLA-DQ Antigens / Q000097:blood / Q000235:genetics*; D059848:HLA-DQ alpha-Chains; D006684:HLA-DR Antigens / Q000097:blood / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006650:Histocompatibility Testing; D006801:Humans; D007129:Immunoglobulin Gm Allotypes / Q000097:blood; D007723:Korea / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
D006683:HLA-DQ Antigens; D059848:HLA-DQ alpha-Chains; C069050:HLA-DQA1 antigen; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; C553502:HLA-DRB1*03:01 antigen; D007129:Immunoglobulin Gm Allotypes