Although the ACPA response in RA has been shown to be citrulline specific, a number of studies have shown false ACPA reactivity with concomitant reactivity to arginine-containing control antigens in inflammatory diseases like pulmonary tuberculosis [22,23], hepatitis C infection with cryoglobulinemia [24], and autoimmune hepatitis [25]. This evidence concerns the gene PRTN3 and rheumatoid arthritis.