Clinical implications of copy number variations in autoimmune disorders.

Human genetic variation is represented by the genetic differences both within and among populations, and most genetic variants do not cause overt diseases but contribute to disease susceptibility and influence drug response. During the last century, various genetic variants, such as copy number variations (CNVs), have been associated with diverse human disorders. Here, we review studies on the associations between CNVs and autoimmune diseases to gain some insight. First, some CNV loci are commonly implicated in various autoimmune diseases, such as Fcγ receptors in patients with systemic lupus erythemoatosus or idiopathic thrombocytopenic purpura and β-defensin genes in patients with psoriasis or Crohn's disease. This means that when a CNV locus is associated with a particular autoimmune disease, we should examine its potential associations with other diseases. Second, interpopulation or interethnic differences in the effects of CNVs on phenotypes exist, including disease susceptibility, and evidence suggests that CNVs are important to understand susceptibility to and pathogenesis of autoimmune diseases. However, many findings need to be replicated in independent populations and different ethnic groups. The validity and reliability of detecting CNVs will improve quickly as genotyping technology advances, which will support the required replication.