BackgroundThe prevalence and incidence of sarcoidosis varies worldwide. We estimated the prevalence and incidence of sarcoidosis in Korea using nationwide claims data from the Korean Health Insurance Review and Assessment Service.MethodsCases of sarcoidosis were identified for any visit between 2007 to 2016 that listed the Korean Classification of Disease, 7th edition code of sarcoidosis and rare incurable disease exempted calculation code. A narrow case definition was used as follows: 1) ≥ two sarcoidosis-coded visits within 1 year of the first claim, 2) no claims for other diseases that could form granuloma.ResultsA total of 4791 patients (narrow, n = 2388) visited medical institutions for sarcoidosis during the study period; 2999 patients (narrow, n = 1696) were newly identified between 2009 and 2015. The sarcoidosis prevalence was 9.37 per 105 people (narrow, 4.69) and was highest between ages 60–69 years. The incidence rate was 0.85 per 105 population at risk (narrow, 0.48), with the highest incidence rate between ages 50–59 years. For incident cases (mean age: 48.5 year), the age distribution in whole population and females showed monophasic patterns peaking at aged 50–59 years, while males had biphasic incidence peak at aged 30–39 years and 60–69 years. The annual incidence rates showed increasing trends from 0.85 per 105 population at risk in 2009 to 0.97 per 105 population at risk in 2015.ConclusionsIn comparison with previous reports, the prevalence and incidence of sarcoidosis in Korea have increased and middle-aged women showed the highest risk.Electronic supplementary materialThe online version of this article (10.1186/s12931-018-0871-3) contains supplementary material, which is available to authorized users.

Sarcoidosis is a systemic granulomatous disorder of unknown cause involving multiple organs. Its clinical presentation and prognosis vary among races. We identified the clinical characteristics and outcomes of Korean patients with sarcoidosis. Clinical data of 367 Korean patients with biopsy-proven sarcoidosis diagnosed in 2001–2017 were retrospectively analyzed. Treatment responses included improvement, stability, or progression based on changes in pulmonary sarcoidosis on chest images. The mean age was 47.4 years, and 67.3% of patients were women. The median follow-up period was 80 months. The highest prevalence was observed in individuals aged 50–59 years (30–39 years in men, 50–59 years in women), and the number of diagnoses showed an increasing trend. Lung involvement was the most common (93.5%), followed by the skin, eyes, and extrathoracic lymph nodes. Among patients with lung involvement and a follow-up period of ≥ 3 months, 66.8%, 31.0%, and 2.2% showed improvement, stability, and progression, respectively. Eleven patients (2.9%) died, and the 5-year survival rate was 99%. The number of diagnosed cases showed an increasing trend, and the mean age at diagnosis was increased compared with that in previous reports. Organ involvement was similar to that of Westerners, although the prognosis appeared better.