- PTPN22 genetic variation: evidence for multiple variants associated with rheumatoid arthritis. Carlton, V.E., Hu, X., Chokkalingam, A.P., Schrodi, S.J., Brandon, R., Alexander, H.C., Chang, M., Catanese, J.J., Leong, D.U., Ardlie, K.G., Kastner, D.L., Seldin, M.F., Criswell, L.A., Gregersen, P.K., Beasley, E., Thomson, G., Amos, C.I., Begovich, A.B. Am. J. Hum. Genet. (2005)