Excellent Response to Leflunomide in a Case of Large-Vessel Giant Cell Arteritis Demonstrated Simultaneously by Clinical, Laboratory, Ultrasound, and Positron Emission Tomography/Computed Tomography Parameters

L arge-vessel giant cell arteritis (LV-GCA) is now recognized as a subgroup that is poorly responsive to glucocorticoids (GCs). More than half of GCA cases relapse during GC tapering, requiring high-dose GC and may fall into this LV-GCA subgroup. It is well recognized that high-dose prolonged GC causes multiple serious adverse events. There is a need for effective and safe steroid-sparing agents. Methotrexate has been studied in 3 trials, and a meta-analysis shows only a modest effect. Tocilizumab, an interleukin 6 receptor inhibitor, has been demonstrated as useful in the GiACTA trial and is now licensed for use in GCA. However, it has significant limitations due to its cost. Leflunomide (LEF), a pyrimidine synthesis inhibitor, is used as a steroid-sparing agent in various rheumatic diseases. Evidence in GCA is limited to case series and an open trial. This clinical case report is to highlight a case of LV-GCA that achieved sustained remission with LEF; as demonstrated by simultaneous improvement in the clinical, laboratory, and imaging parameters. A 66-year-old woman presented with fatigue, night sweats, weight loss, scalp tenderness, jaw pain, episode of melena, abdominal cramps, and raised C-reactive protein (89 mg/L [reference, <5 mg/L]). Computed tomography (CT) colonoscopy, undertaken to exclude serious pathology, showed circumferential, longitudinal thickening in the aortic wall. On examination, she looked unwell and underweight with poor muscle mass with tenderness in the left axilla. Temporal artery ultrasound (US) was normal, but the axillary artery US suggested LVV with hypoechoic intimal medial thickness (IMT) of 2.1 mm bilaterally with the “slope sign” (Figure). Positron emission tomography (PET)/CT showed extensive evidence of LVV involving the entire length of aorta, carotids, axillary, common iliac, and femoral vessels (Figure). She was started on oral prednisolone 40 mg daily and LEF 20 mg daily. Leflunomide causes blockade of dendritic cells and interleukin 6, pathways that have incriminated in the pathogenesis of GCA. At 6 weeks' follow-up, her constitutional symptoms and jaw pain were completely resolved; however, she experienced