At present, the most reported etiology of IAS involves the production of IAAs induced by external factors due to the HLA-DRB1 genotype and some autoimmune diseases (such as Graves’ disease, systemic lupus erythematosus, and systemic sclerosis).[8] Viruses and drugs are the 2 most important causes. This evidence concerns the gene HLA-DRB1 and systemic sclerosis.