Relapses and flares are the same thing? and can happen without increase in CRP ESR when tapering prednisone.
Disease Relapses among Patients with Giant Cell Arteritis: A Prospective, Longitudinal Cohort Study. exerpt
"The most common symptoms at relapse were headache (42%) and polymyalgia rheumatica (51%), but ischemic (some transient) manifestations (visual symptoms, tongue or jaw claudication, and/or limb claudication) occurred in 29% of relapses (12% cohort). Forty-three relapses (73%) occurred while patients were taking glucocorticoid therapy at a median (range) prednisone dose of 7.5 (0-35) mg. In 21% of relapses, both erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were normal."