Small-vessel vasculitis surrounding a spared temporal artery - Clinical and pathologic findings in a series of twenty-eight patients

Objective. Occasionally, a temporal artery biopsy reveals small-vessel vasc ulitis (SW) surrounding a spared temporal artery, the significance of which is unclear. We analyzed the final diagnosis in a series of patients with t his 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 SW surrounding a spared temporal artery was the first histologic fi nding 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 no rmal findings on muscle biopsy and electrophysiologic study. Three patients had systemic necrotizing vasculitis (SNV), based on the demonstration of t ypical lesions on subsequent muscle, nerve, or kidney biopsy. After extensi ve evaluation, 4 patients remained unclassifiable. Nine patients were incom pletely studied. Fibrinoid necrosis was significantly more frequent in pati ents with SNV (P = 0.0022), whereas involvement of vasa vasorum was more fr equent in patients classified as having GCA (P = 0.022). No differences in the pattern of small vessel involvement were found in patients with SW surr ounding a spared temporal artery who were classified as having GCA compared with patients with biopsy-proven GCA. Granulocytes were observed at simila r frequency in all conditions. Conclusion. SW may be the only abnormal feature in a temporal artery biopsy and the only histologic evidence of vasculitis. The diagnosis of GCA can b e reasonably established in most of these patients when there is no apparen t evidence of additional organ involvement. However, when fibrinoid necrosi s is observed or the temporal artery vasa vasorum are not involved, SNV mus t be extensively excluded.