Giant cell arteritis.

Giant cell arteritis (GCA) is a medium and large-vessel vasculitis, which is an important cause of secondary headache in older adults. While GCA has a classic presentation occurring after the age of 50, atypical presentations (eg, fever of unknown origin, cough, low or normal erythrocyte sedimentation rate) may lead to a delay in diagnosis. The topography of vascular involvement has implications for disease-related complications, which can result in neurologic disease at multiple levels of the nervous system. The most feared complication, vision loss, fortunately becomes uncommon after initiation of corticosteroids. Corticosteroid treatment should not be withheld while waiting the results of a temporal artery biopsy (TAB), which remains the gold standard for GCA diagnosis. Newer diagnostic modalities, including ultrasound, magnetic resonance imaging, and positron emission tomography can play an important role in directing treatment in cases with negative TAB. After successful control of the disorder, patients should be gradually tapered off corticosteroids, with careful monitoring using both clinical and laboratory parameters to assess for relapse. Corticosteroid-related treatment complications are not uncommon in GCA. There is mixed evidence for use of adjunct corticosteroid-sparing agents (eg, methotrexate), although these should be initiated in the setting of corticosteroid-related morbidity and/or cases with frequent relapse.