Among these, IRAK1 (interleukin 1 receptor associated kinase) was the first X chromosome locus reported as associated with RA susceptibility and is thus of importance given the female predominance of the disease. IRAK1 is a serine-threonine protein kinase and an essential component of the toll/interleukin 1 receptor (TIR) signaling pathway involved in the pathogen-mediated inflammation [16]. This evidence concerns the gene IRAK1 and rheumatoid arthritis.