Because there is strong evidence implicating these two genes in RA, and because the effect of PTPN22 variants may be restricted to rheumatoid factor-positive patients, the purpose of our study is twofold: first, to estimate the genetic model (including penetrances) associated with these two genes in White nuclear families from the North American Rheumatoid Arthritis Consortium (NARAC) data; and second, to model PTPN22 susceptibility conditional on the rheumatoid factor status in RA patients. Here, PTPN22 is linked to rheumatoid arthritis.