LAUSR

OBJECTIVE We conducted a nationwide epidemiological study to estimate the number of patients with Takayasu arteritis (TAK) and giant cell arteritis (GCA) in Japan and to describe the clinical characteristics of these patients. METHODS The first survey was designed to estimate the number of patients with TAK and GCA who were treated at medical institutions in Japan in 2017. The second survey was designed to collect data on the clinical characteristics of the patients who were reported in the first survey. RESULTS Of the 3,495 institutions selected for the first survey, 1,960 (56.1%) responded. The number of patients with clinically diagnosed TAK and GCA was estimated to be 5,320 (95% confidence interval [CI], 4,810-5,820) and 3,200 (95% CI, 2,830-3,570), respectively. Aortic regurgitation was reported in 35% of patients with TAK, and eye-related comorbidities were observed in 30.4% of patients with GCA. The common carotid and internal carotid arteries were the most frequently involved in patients with TAK (62.7%). Subclavian artery lesions and thoracic or abdominal aorta lesions were reported in 31% and 42.6% of patients with GCA, respectively. CONCLUSIONS The number of patients with TAK and GCA was estimated simultaneously, and significant differences in clinical characteristics were observed between the two diseases.