Giant cell arteritis (GCA) is a systemic vasculitis that primarily affects large and medium-sized arteries, especially the cranial arteries, resulting in classic symptoms such as acute onset headache, visual disturbances, jaw claudication, and stroke [1]. Despite a prevalence of 7.3 per 100,000 in Northern Europe, GCA is the most common vasculitis among individuals over 50 years old [2]. It predominantly affects elderly Caucasians in Northern Europe, whereas Takayasu arteritis, another type of large vessel vasculitis, mainly affects young Asian women. GCA is extremely rare in Black and Asian populations. In Japan, the prevalence of GCA is estimated at 1.47 per 100,000 among individuals over 50 years old, and its prevalence in South Korea has not been accurately estimated to date [3].

Given the geographic and ethnic variations in GCA prevalence, it is unclear whether clinical features, treatment responses, and prognoses observed in Western populations can be generalized to Korean patients with GCA. Therefore, the study by Lee et al. [4] in this issue is a significant contribution, as it describes the clinical characteristics of a relatively large retrospective multi-center cohort of 27 Korean patients with GCA.

The clinical characteristics of Korean GCA patients are similar to those reported in studies from Western countries from countries like France and the USA (Table 1) [5-7]. As a mean age at diagnosis was 75 years, the incidence of GCA is expected to rise in Korea’s aging population [8]. Concomitant polymyalgia rheumatica (PMR) was present in 50% of the Korean patients, compared to 34.5% and 44.3% in Western studies. PMR is notably rare in Korea, with a prevalence of 0.0082% (8.21 per 100,000), compared to 0.6% in a previous study [2,7], suggesting that both GCA and PMR, which share similar pathophysiology, are very rare in South Korea, possibly due to genetic factors.

Table 1 . Characteristics of Korean and Western GCA patients [5-7].

	Korea (n=27)	Western (n=693)	Western (n=286)
Age at diagnosis (yr)	75.0 [71.0~79.0]	75 [48~94]	75.0±7.6
Sex, female	17 (63.0)	486 (70.1)	213 (74.5)
Duration of symptoms (wk)	5.5 [1.0~8.0]		8.4 [3.6~17.6]
Fever at onset	12 (44.4)	229 (33.0)	57 (20.4)
Positive TAB	15/16 (93.8)	632 (91.2)
Visual ischemia complication	9 (33.3)	215 (31.0)	36 (12.7)
Concurrent PMR	14 (51.9)	239 (34.5)	36 (12.6)
ESR (mm/hr)	98.0 [74.5~111.0]		66.0 [42.5~93.5]
CRP (mg/dL)	9.09 [5.91~15.86]	8.3 [0.1~53.5]	5.47 [2.30~10.05]
Large vessel involvement	12 (44.4)	173/310 (55.8)
Relapse	4 (14.8)	354 (51.1)	213 (74.5)
Median follow-up duration (mo)	33.8	49.9	61.2
Factors associated with relapse	Absence of fever at onset Vision loss at onset		Established HTN/DM at diagnosis Female
Permanent vision loss	4 (14.8)		16 (5.7)
Initial GC dose	60.0 [50.0~60.0] mg/d*	0.73 [0.25~1.6] mg/kg/d	50.8±13.1 mg/d*
Use of GC-sparing agents	22 (81.5)	124 (17.9)

Values are presented as median [interquartile ranges], mean±standard deviation, or number (%). GCA: giant cell arteritis, TAB: temporal artery biopsy, PMR: polymyalgia rheumatica, ESR: erythrocyte sedimentation rate, CRP: C-reactive protein, HTN: hypertension, DM: diabetes mellitus, GC: glucocorticoids. *Prednisolone-equivalent dose. Reused from the article of de Boysson et al. (Clin Exp Rheumatol 2019;37 Suppl 117:57-60) [5], Labarca et al. (Rheumatology (Oxford) 2016;55:347-56) [6], Kim et al. (J Rheum Dis 2014;21:297-302) [7]..

The most serious complication of GCA is vision loss to anterior ischemic optic neuropathy. Visual ischemic complications were quite common, occurring in 33.3% of Korean GCA patients at baseline, comparable to the previously reports [9]. However, the rate of permanent vision loss in Korean GCA patients was high at 14.8%, compared to 5.7% in Western population. This underscores the importance of early diagnosis and treatment to prevent blindness.

The treatment response in Korean GCA patients was favorable, with a relapse rate of only 14.8%, compared to 51.1% and 74.5% in Western studies. This lower relapse rate may be attributed to the higher use of glucocorticoid-sparing agents in Korean patients.

While the study by Lee et al. [4] provides valuable insights into Korean patients with GCA, further large-scale epidemiologic studies are needed to accurately estimate the incidence and prevalence, and clinical characteristics of both GCA and PMR in South Korea. Additionally, it is necessary to assess the therapeutic efficacy, including the novel treatment options such as interleukin-6 inhibitors, and long-term outcome in Korean patients with GCA.

In conclusion, although GCA is rare in South Korea, it can lead to severe complications, including permanent vision loss. Therefore, elderly patients presenting with headaches and elevated inflammatory markers should be promptly evaluated for GCA.