Cranial and extracranial giant cell arteritis share similar HLA-DRB1 association

To determine whether giant cell arteritis (GCA) patients with the typical pattern of cranial ischemic manifestations and those with the extracranial large-vessel-vasculitis (LVV)-GCA phenotype exhibit different HLA-DRB1 association. 178 biopsy-proven GCA patients who had cranial ischemic features but no LVV manifestations, 100 patients with LVV-GCA without cranial ischemic manifestations and 486 ethnically matched healthy controls were recruited. All patients and controls were Spanish of European ancestry. We compared HLA-DRB1 phenotype frequencies between the three groups. Both GCA subgroups had well-differentiated clinical features. Patients with LVV-GCA were younger (68.0 ± 10.0 years versus 74.0 ± 10.4 years; p < 0.01) and presented more commonly with polymyalgia rheumatica symptoms (81% versus 39.3%; p < 0.01) than those with the classic cranial GCA phenotype. HLA-DRB1*04 phenotype frequency was significantly increased in patients with classic cranial GCA compared to controls (42.1% versus 23.5%, respectively; p < 0.01; odds ratio-OR [95% confidence interval-CI] = 2.38 [1.62–3.47]). This association was mainly due to the HLA-DRB1*04:01 allele (20.8% versus 5.3%, respectively; p < 0.01; OR [95% CI] = 4.64 [2.63–8.26]). HLA-DRB1*04 association was also observed in LVV-GCA patients when compared to controls (46.0% versus 23.5%, respectively; p < 0.01; OR [95% CI] = 2.78 [1.73–4.44]). Similar to cranial GCA, the association was also mainly due to the HLA-DRB1*04:01 allele (19.0% versus 5.3%, respectively; p < 0.01; OR [95% CI] = 4.15 [2.06–8.19]). Cranial and LVV-GCA patients did not exhibit HLA-DRB1 allele differences. Cranial and extracranial LVV-GCA share similar HLA-DRB1 association.