- Lack of association of a functional single nucleotide polymorphism of PTPN22, encoding lymphoid protein phosphatase, with susceptibility to biopsy-proven giant cell arteritis. Gonzalez-Gay, M.A., Oliver, J., Orozco, G., Garcia-Porrua, C., Lopez-Nevot, M.A., Martin, J. J. Rheumatol. (2005)