Background/Purpose:

Temporal artery biopsy is the gold standard for diagnosing giant cell arteritis (GCA). The pathology of GCA characteristically involves transmural infiltrates, giant cell formation and intimal hyperplasia. However the significance of histopathology characteristics, in terms of clinical features and complications of GCA, remains unknown. The aim of this study was to investigate the association between histological biopsy features and clinical features, such as blindness, in patients with biopsy positive GCA.

Methods:

Positive temporal artery biopsies registered on the South Australian Giant Cell Arteritis Registry were identified between 1991 and 2013 (n=186). Clinical and serological data was recorded using both patient questionnaire and case note review. Patients without clinical data were excluded from the analysis (n=42). Statistical analysis was performed using chi-squared and Wilcoxon’s tests.

Results:

144 biopsy positive GCA cases were analysed. The mean age at biopsy was 77 years. 71% were female, and in total 30% experienced blindness. Although not individually significant, transmural inflammation (p = 0.11), luminal thrombus (p = 0.17) and giant cells (p = 0.20) were more frequent in GCA patients with blindness, whereas fragmentation of the internal elastic lamina (p = 0.04), and intimal thickening (p = 0.02) were more frequent in GCA patients without blindness (Table 1). The presence of giant cells was associated with transmural inflammation (p = 0.06), jaw claudication (p = 0.02), and higher inflammatory markers. In contrast, characteristics of patients with intimal thickening included a lower frequency of giant cells (0.01) and jaw claudication (p = 0.01), and lower inflammatory markers.

Table 1: Association Between Histopathology and Blindness

Conclusion:

Giant cells are strongly associated with jaw claudication and systemic markers of inflammation. We did not find any histological features that were individually significantly associated with an increased risk of blindness in GCA patients. However patients with intimal thickening by histology are less likely to have giant cells, have less acute systemic inflammation, and have a lower risk of blindness. This group may reflect a different disease subgroup or late stages of inflammation, highlighting the challenges in the pathological diagnosis and biopsy reporting of active GCA.