It is known that such changes, caused by peptidyl arginine deiminase 4 (PAD4), converts arginine residues to citrullinated residues which may confer autoimmune epitopes on histones, resulting in autoantibodies which may exacerbate autoimmune diseases, such as small-vessel vasculitis and SLE (58, 59). This evidence concerns the gene PADI4 and autoimmune disease.