Objective: Occasionally, a temporal artery biopsy reveals small-vessel vasculitis (SVV) surrounding a spared temporal artery, the significance of which is unclear. We analyzed the final diagnosis in a series of patients with this condition and tried to identify histopathologic features with potential usefulness in predicting the ultimate diagnosis.
Methods: We performed a clinical and histopathologic review of 28 patients in whom SVV surrounding a spared temporal artery was the first histologic finding that led to the diagnosis of vasculitis. For comparison purposes, we analyzed the pattern of small vessel involvement in 30 patients with biopsy-proven giant cell arteritis (GCA).
Results: GCA was considered the most likely diagnosis in 12 patients, based on the absence of clinical evidence of additional organ involvement and normal findings on muscle biopsy and electrophysiologic study. Three patients had systemic necrotizing vasculitis (SNV), based on the demonstration of typical lesions on subsequent muscle, nerve, or kidney biopsy. After extensive evaluation, 4 patients remained unclassifiable. Nine patients were incompletely studied. Fibrinoid necrosis was significantly more frequent in patients with SNV (P = 0.0022), whereas involvement of vasa vasorum was more frequent in patients classified as having GCA (P = 0.022). No differences in the pattern of small vessel involvement were found in patients with SVV surrounding a spared temporal artery who were classified as having GCA compared with patients with biopsy-proven GCA. Granulocytes were observed at similar frequency in all conditions.
Conclusion: SVV may be the only abnormal feature in a temporal artery biopsy and the only histologic evidence of vasculitis. The diagnosis of GCA can be reasonably established in most of these patients when there is no apparent evidence of additional organ involvement. However, when fibrinoid necrosis is observed or the temporal artery vasa vasorum are not involved, SNV must be extensively excluded.