Analysis of HLA-DM polymorphism in juvenile dermatomyositis (JDM) patients.

Annually approximately 1:200,000 young children and adolescents are affected by juvenile dermatomyositis (JDM). Genetic factors are thought to contribute to the etiology. Since the discovery of the human leukocyte antigen class II associated DM molecule much has been learned about its role in the normal processing of HLA-class II molecules with a limited number of polymorphisms being found. Blood samples were collected from 30 patients who were seen in the clinic and 40 healthy volunteers. Exon 3 of the HLA-DM A and B genes were amplified and specific polymorphisms were identified given allele designations. The DMA*0103 allele was found in 43% of patient alleles versus 8% in the control group, this difference reached significance at a p value of 0.0004. The DMB*0102 allele was found in 20% of patients compared with 3% of the controls with a calculated p value of 0.037. Relative risk (RR) ratios with CI were as follows: DMA*0103 vs control RR = 5.7 and DMB*0102 vs control RR = 8. In conclusion, we feel that the polymorphisms represented in the DMA*0103 and the DMB*0102 alleles are increased in frequency in our JDM patients.