The JIIMs, like other autoimmune disorders, appear to be comprised of a number of clinical and serological phenotypes, each of which defines more homogeneous subsets of patients in terms of demographic features, the presence of certain myositis-associated autoantibodies, immunogenetics and outcomes [2, 3] . For example, patients with anti-p155 autoantibodies form a phenotype characterized by the frequent presence of cutaneous involvement and characteristic photosensitive rashes of JDM and the HLA-DQA1*0301 allele, whereas patients with anti-synthetase autoantibodies frequently have moderate to severe weakness, arthritis, RP, mechanic's hands, fevers, interstitial lung disease and HLA DRB1*0301 [3] [4] [5] . Clinical features of illness also appear to differ by age, gender, race and even disease course phenotypes [6] [7] [8] . Such homogeneous phenotypes might share unique combinations of environmental and genetic risk factors that result in a discrete disorder [9] .