P4HA2 and temporal arteritis: Previous attempts to uncover the genetic basis of giant cell arteritis through large-scale genetic approaches led to the identification of two loci associated with the disease, P4HA2 and PLG, and substantiated the crucial involvement of the HLA region in disease susceptibility.3, 4 The identified signals indicated a genetic contribution of the angiogenesis process in disease pathogenesis, further supporting the proposed role of this mechanism in giant cell arteritis.