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Objective. Ankylosing spondylitis (AS) is a chronic inflammatory disease with obvious male preponderance. Males show more severe radiographic manifestations compared with females. This study aimed to evaluate the effects of sex and estrogen on the radiographic progression of AS. Methods. A total of 101 patients with AS were included in this study. All of the radiographs were scored using the modified Stoke AS Spine Score (mSASSS). Serum levels of 17β-estradiol (E2), dickkopf-1 (Dkk1), and leptin were detected by enzyme-linked immunosorbent assay. The generalized estimating equations model was used to evaluate factors associated with spinal radiographic progression. Results. The mean age at disease onset was 27.3±10.7 years, and 16 patients (15.8%) were female. In the multivariable analysis, body mass index (β-coefficient=0.12; p=0.047) and levels of Dkk1 (β-coefficient=-0.11; p＜0.001), and female (β-coefficient=-1.40; p=0.001) were associated with radiographic progression. Among male patients with AS, baseline C-reactive protein (β=0.11; p=0.005) and mSASSS (β=0.21; p=0.030) were also associated with radiographic progression. E2 and leptin levels were not significantly related to the radiographic progression. Conclusion. Although female patients were associated with less radiographic progression in AS, there was no significant relationship between serum estrogen level and radiographic progression. Results of current study suggests that genetic factors or other environmental factors associated with female may influence radiographic progression in patients with AS. (J Rheum Dis 2021;28:76-84)

Objective. This cross-sectional study aimed to investigate the association between rheumatoid factor (RF) positivity and bone mineral density (BMD) in male Korean subjects without any history of joint disease. Methods. Of 84,344 males who had undergone a comprehensive health checkup program in 2012, 1,390 male health examinees were recruited, whose BMD and RF results were available. A RF titer ≥20 IU/mL was considered positive. BMD was measured at lumbar spine (L1∼L4) or hip (femoral neck and total hip) by dual-energy X-ray absorptiometry. Results. The association between RF positivity and BMD was assessed by multiple linear regression analysis. The mean age was 52.7±10.9 years (range 19∼88 years), and RF was detected in 64 subjects (4.6%). Demographics and laboratory data were not different between RF-positive and -negative subjects except hepatitis B surface antigen (HBsAg), which was more frequently seen in RF-positive subjects (15.6% vs. 4.3%, p=0.001). RF-positive subjects had significantly lower BMD compared to RF-negative subjects in lumbar spine but not in total hip regardless of the existence of HBsAg (1.17±0.16 g/㎠ vs. 1.10±0.18 g/㎠, p=0.002 in total subjects; 1.17±0.16 g/㎠ vs. 1.10±0.18 g/㎠, p=0.004 in HBsAg-negative subjects). After adjusting for multiple confounders, RF positivity was negatively associated with lumbar spine BMD (B=-0.088 and standard error=0.035, p=0.011). Conclusion. Our results show that the presence of RF could have an unfavorable impact on bone density in apparently normal males. Additional studies to elucidate the osteoimmunological mechanism of rheumatoid factor are warranted. (J Rheum Dis 2019;26:31-40)

Objective. To estimate the prevalence of non-adherence to rheumatoid arthritis (RA) medication and identify the associated factors for non-adherence in RA patients. Methods. Among the KORean Observational study Network for Arthritis 3,523 patients who completed a questionnaire about the adherence to RA medication were analyzed. The patients were divided into two groups: 1) adherent group, patients who skipped medication ≤5 days within the past 2 months; and 2) non-adherent group, patients who skipped ≥6 days of medication. The baseline characteristics were compared, and multivariable regression analysis was performed to identify the associated factors for non-adherence. Results. The non-adherent group had 339 patients (9.6%). The common causes of non-adherence were forgetfulness (45.8%), absence of RA symptoms (24.7%), and discomfort with RA medication (13.1%). Younger age (odds ratio [OR] 1.02, p＜0.01) and higher income (OR 1.70, p＜0.01) were associated with an increased risk of non-adherence. Whereas higher functional disability (OR 0.68, p＜0.01) and oral corticosteroid use (OR 0.73, p=0.02) were associated with a decreased risk of non-adherence. The associated factors differed according to cause of non-adherence. Having adverse events (OR 2.65, p=0.02) was associated with the risk of non-adherence due to discomfort with RA medication while a higher level of education (OR 2.37, p=0.03) was associated with the risk of non-adherence due to an absence of RA symptoms. Conclusion. The 9.6% of Korean RA patients were non-adherent to RA medication. The associated factors differed according to the cause of non-adherence. Therefore, an individualized approach will be needed to improve the adherence to RA medication. (J Rheum Dis 2018;25:47-57)

Objective. Polymyalgia rheumatica is a chronic inflammatory disease that affects people older than 50 years of age. The diagnosis is made based on clinical features, and the current standard of treatment is low-dose glucocorticoids. PMR is more commonly reported in Caucasians and females. However, epidemiological studies of PMR in Asian countries are scarce. We aimed to estimate the epidemiology of PMR in Korea. Methods. This study was conducted by analyzing the Health Insurance Review and Assessment databases. We verified all claims between 2007 and 2012. Cases were included when PMR ICD-10 code (M 35.3) was recorded more than twice, and glucocorticoids were prescribed for ≥30 days. Results. We identified 1,463 newly diagnosed cases of PMR during the 5 years. Among them, 992 (67.8%) were female, and the mean age at diagnosis was 66.9 years old. The annual incidence rate was 2.06 per 100,000 individuals aged over 50 years. The prevalence rate was 8.21 per 100,000 individuals in 2012. Incidence and prevalence appeared to increase with age. Prednisolone was the most commonly prescribed glucocorticoid. In half of the patients, the daily starting dose was 6∼15 mg as prednisolone equivalents. Conclusion. This is the first study to investigate the epidemiology of PMR in Korea. The incidence and prevalence appeared to be considerably lower than those in Western populations. Both genetic and environmental factors might influence disease occurrence. In addition, the actual incidence may have been underestimated due to lack of awareness of PMR in clinical practice.

Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Department of Internal Medicine, Yonsei Unversity College of Medicine 2 , Seoul, Department of Rheumatology, Ajou University Hospital, Suwon, Division of Rheumatology, Daejeon Rheumatoid & Degenerative Arthritis Center, Chungnam National University 4 , Daejeon, Division of Rheumatology, Department of Internal Medicine, Korea University Anam Hospital, Division of Rheumatology, Department of Internal Medicine, Ewha Womans University Mokdong Hospital, Division of Rheumatology, Department of Medicine, Sungkyunkwan University, School of Medicine, Samsung Medical Center, Seoul, Korea