Factors associated with sarcopenia in Japanese patients with rheumatoid arthritis: results from the IORRA cohort study

To investigate the prevalence of and factors associated with sarcopenia in Japanese patients with rheumatoid arthritis (RA). We analyzed a cross-section of patients with RA participating in the Institute of Rheumatology Rheumatoid Arthritis cohort survey in 2021. Participants completed self-administered questionnaires, including a 5-item sarcopenia screening index (SARC-F). Patients with a SARC-F score of 4 or higher were categorized as having sarcopenia. Among 2416 Japanese patients with RA (2113 women and 303 men; mean age 63.9 years), 341 (14.1%) patients were categorized as having sarcopenia. In a multivariable analysis of patients of all ages, age, body mass index (BMI), disease duration, history of fracture, patient pain on a visual analog scale (VAS), patient or physician global assessments based on VAS, and use of nonsteroidal anti-inflammatory drugs (NSAIDs), biologic disease-modifying antirheumatic drugs (bDMARDs), and corticosteroids were significantly (P < 0.05) associated with sarcopenia. Disease duration, patient global assessments based on VAS, and use of NSAIDs and bDMARDs were significantly associated with sarcopenia among the patients aged < 65 years, whereas age, female sex, BMI, disease duration, history of fracture, patient pain VAS and global assessments based on VAS, and use of bDMARDs and corticosteroids were significantly associated with sarcopenia in patients aged ≥ 65 years. In Japanese patients with RA, age, BMI, disease duration, history of fracture, patient pain VAS and global assessments based on VAS, and use of NSAIDs, bDMARDs, and corticosteroids were associated with sarcopenia. Among older patients with RA, female sex was additionally associated with sarcopenia. Key Points • To our knowledge, this is the first report showing factors associated with sarcopenia in Japanese patients with rheumatoid arthritis using a large cohort database. • Age, BMI, disease duration, history of fracture, patient pain on a visual analog scale, and use of nonsteroidal anti-inflammatory drugs, biologic disease-modifying antirheumatic drugs, and corticosteroids were associated with sarcopenia in Japanese patients with rheumatoid arthritis. Limited to elderly patients, female sex was also associated with sarcopenia.

The efficacy of general anesthesia during pulmonary vein isolation compared with conscious sedation

Background

Catheter ablation (RFA) is significantly more effective in terms of arrhythmia recurrence rate than antiarrhythmic medication. For the duration of the procedure, the patient needs to remain motionless on the operation table. General anesthesia (GA) is widely used during atrial fibrillation (AF) ablation in all over the world, however RFA of AF is performed under conscious sedation (CS) in the most centers in Japan.

It remains controversial whether cardiac anesthesiologists are best suited to manage anesthesia in the electrophysiology lab.

Objective

The aim of this study was to report the efficacy and safety of GA during AF ablation.

Methods

297 patients (67.3±11.7 years, 208 men, 128 paroxysmal, mean follow up 443 days±306) with AF undergoing RFA in our department from January 2018 to December 2021 were retrospectively analyzed. 113 assigned to the GA group, 184 patients to the CS group.

The primary efficacy end point was radiofrequency time, ablation index, force time integral. The secondary end points defined AF recurrence and the complications.

Result

There was no difference in the baseline characteristics between the two groups. There was no difference between groups in AF recurrence (22.1% vs. 14.1%, P=0.103) and complications.However, Patients in GA had shorter radiofrequency times (66.9±3.7 minute vs 79.0±2.9 minutes P=0.01)Ablation index (376±18.6 vs 371±22.6 P&lt;0.05), Force time integral (136±22.3 vs 111.4±45.3).

Conclusion

General anesthesia is superior to conscious sedation with shorter radiofrequency times and higher than Force time integral, ablation index. Moreover, it is not inferior in regard to arrhythmia recurrence or complication rates of catheter ablation of atrial fibrillation.

Funding Acknowledgement

Type of funding sources: None.

Clinical Observations of Osteoporosis in Japanese Patients with Rheumatoid Arthritis

Osteoporosis is the one of the major adverse outcomes in patients with rheumatoid arthritis (RA). Recently, we and others have been reported many clinical observations related to osteoporosis in Japanese RA patients. In this article, I reviewed these findings. Japanese patients with RA have a two-fold risk of fractures compared with those without RA. Among the fractures in Japanese RA patients, three quarters of the fractures were non-vertebral fractures. The incidence of non-vertebral fractures did not change, despite an improvement in RA disease activity. Older age, female gender, history of fractures, history of total knee replacements, disease activity scores in 28 joints (DAS28), health assessment questionnaire disability index (HAQ-DI), low bone mineral density, glucocorticoid dose, and vitamin D deficiency were significantly associated with fractures. Older age, high body mass index (BMI), HAQ-DI, and polypharmacy were significantly associated with falls. BMI (both overweight and underweight), DAS28, and HAQ-DI were significantly associated with frailty. Half and three quarters of Japanese men and women with RA had vitamin D deficiency, respectively. The incidence of osteonecrosis of the jaw may be higher in Japanese RA patients than those without RA. Undertreatment of osteoporosis appears to exist in Japanese patients with RA.

Factors associated with frailty in Japanese patients with rheumatoid arthritis: results from the Institute of Rheumatology Rheumatoid Arthritis cohort study

This study aimed to evaluate the prevalence of, and the factors associated with, frailty in Japanese patients with rheumatoid arthritis (RA). Patients with RA enrolled in the Institute of Rheumatology Rheumatoid Arthritis (IORRA) cohort completed self-administered questionnaires, which included the 5-item frailty screening index. Patients were classified as frail, prefrail, or robust based on the 5 components of the frailty screening index. Logistic regression analyses were used to evaluate associations between clinical variables and frailty. Among 3,290 Japanese patients with RA (86.7% female, mean age 62.4 years) who participated this frailty study, 549 (16.7%) patients were categorized as frailty, 2,063 (62.7%) as prefrailty, and 678 (20.6%) as robust. In multivariable models, body mass index (BMI) ≥ 25 kg/m² (odds ratio [OR] 1.87, 95% confidence interval [CI] 1.41 to 2.47), BMI < 18.5 kg/m² (OR 1.31, 95% CI 1.00 to 1.71), disease activity scores in 28 joints (DAS28) (OR 1.32, 95% CI 1.18 to 1.47), Japanese version of Health Assessment Questionnaire disability index (J-HAQ) (OR 1.26, 95% CI 1.04 to 1.52), the European Quality of Life-5 Dimensions (EQ-5D) (OR 0.80, 95% CI 0.74 to 0.85), non-steroidal anti-inflammatory drug (NSAID) use (OR 1.59, 95% CI 1.23 to 1.98), and methotrexate (MTX) use (OR 0.75, 95% CI 0.60 to 0.94) were significantly (P < 0.05) associated with frailty. BMI (both overweight and underweight), DAS28, J-HAQ, EQ-5D, NSAID use, and MTX nonuse appear to be associated with frailty in Japanese patients with RA. Key Points • This is the largest study showing the prevalence and the associated factors of frailty in patients with RA. • Maintaining normal BMI appears to be important for preventing frailty in patients with RA. • We confirmed the significant associations of frailty with high disease activity, high degree of disability, and poor health related QOL in Japanese patients with RA. • NSAID use and MTX nonuse were associated with the frailty in Japanese patients with RA, which could be explained by patients' background.

Safety and efficacy of a hyperaemic agent, intracoronary nicorandil 4mg, for invasive physiological assessments during fractional flow reserve measurement

Background

Fractional flow reserve (FFR) is one of most reliable index for the determining the functional severity coronary artery stenosis. Adenosine is the most commonly used agent for maximal hyperaemia. However, adenosine can cause chest discomfort, bronchial hyper-reactivity, and atrioventricular block. The aim of this study is to evaluate the safety and efficacy of intracoronary nicorandil as an alternative hyperaemic agent for FFR.

Methods and results

We enrolled consecutive 82 patients (87 lesions) who underwent FFR measurement in our center from Nov. 2018. We compared three groups; intravenous infusion of adenosine (150 μg/kg/min); and adenosine added intracoronary nicorandil 2mg; and intracoronary nicorandil 4mg. Mean FFR value was 0.83±0.09, 0.82±0.09, 0.82±0.08, There was a strong correlation among three groups (R2&gt;0.9). Mean cyclic change in FFR was 0.026±0.023, 0.019±0.010, 0.016±0.014, respectively, cyclic change was smallest in intracoronary nicorandil 4mg group (vs ATP; p&lt;0.001, vs ATP + nicorandil 2mg; p&lt;0.001). By Wilcoxon test, mean FFR value of nicorandil 4mg was significant lower than ATP (p=0.0021), and equal to ATP + nicorandil 2mg (p=0.98).

Conclusions

Intracoronary nicorandil 4mg is a simple, safe, and effective way to induce steady-state hyperaemia for FFR.

Figure 1

Funding Acknowledgement

Type of funding source: None

Factors associated with osteoporosis medication use in Japanese patients with rheumatoid arthritis: Results from the Institute of Rheumatology Rheumatoid Arthritis cohort study

Objectives

This study aimed to evaluate factors associated with osteoporosis medication use in Japanese patients with rheumatoid arthritis (RA).

Methods

Patients with RA who enrolled in our cohort completed self-administered questionnaires which included questions regarding their osteoporosis medications. Logistic regression was used to determine the association of variables with the use of these medications.

Results

Among 5660 Japanese patients with RA who responded to the questionnaires (mean age, 61.8 years; 86.0% female), 1983 patients (35.0%) and 1211 patients (21.4%) reported taking osteoporosis medications and antiresorptive agents, respectively. In multivariate models, age, female sex, lower body mass index (BMI), self-reported fracture history, Japanese Health Assessment Questionnaire-Disability Index (JHAQ-DI), daily dosage of prednisone (PSL), weekly dosage of methotrexate (MTX), and concomitant use of hypertension and hyperlipidemia medications were significantly associated with the use of osteoporosis medications (P < 0.05). Among women with RA, the use of hypertension medications was significantly correlated with the use of both osteoporosis medications and antiresorptive agents (P < 0.05).

Conclusions

Age, female sex, a lower BMI, duration of RA, self-reported fracture history, JHAQ-DI, daily dosage of PSL, weekly dosage of MTX, and the use of medications for hypertension and hyperlipidemia appear to be associated with the use of osteoporosis medications in Japanese patients with RA.

Age and female gender associated with periodontal disease in Japanese patients with rheumatoid arthritis: Results from self-reported questionnaires from the IORRA cohort study

Objectives: This study aimed to evaluate the prevalence of, and the factors associated with, periodontal disease in Japanese patients with rheumatoid arthritis (RA).Methods: Patients with RA enrolled in the Institute of Rheumatology Rheumatoid Arthritis (IORRA) cohort completed three self-administered questionnaires including questions about recent gingival bleeding during toothbrushing, a recent diagnosis of periodontitis by a dentist, and any history of periodontitis. Logistic regression analyses were used to evaluate associations with clinical variables for each questionnaire.Results: Among 5600 Japanese patients with RA, 31.0%, 18.3%, and 20.4% of patients self-reported recent gingival bleeding during toothbrushing, a recent diagnosis of periodontitis by a dentist, and a history of periodontitis, respectively. In multivariate models, younger age, fracture history, Japanese Health Assessment Questionnaire-Disability Index (JHAQ-DI), and prednisolone dosage were significantly (p < .05) associated with recent gingival bleeding during toothbrushing. Older age, female gender, and ever-smoker status were significantly correlated with a recent diagnosis of periodontitis.Conclusion: Many Japanese patients with RA experience gingival bleeding during toothbrushing and are diagnosed with periodontitis. Age, female gender, ever-smoker status, fracture history, JHAQ-DI, and prednisolone dosage appeared to be associated with periodontal disease in Japanese patients with RA.

Distribution of gene segments of the pandemic A(H1N1) 2009 virus lineage in pig populations

Swine influenza viruses (SIVs) are important not only for pig farming, but also for public health. In fact, pandemic A(H1N1) 2009 viruses [A(H1N1)pdm09] were derived from SIVs. Therefore, timely characterization of locally circulating SIVs is necessary for understanding the global status of SIVs. To genetically characterize SIVs circulating in Japanese pig populations, we isolated 24 SIVs of three subtypes (17 H1N1, four H1N2 and three H3N2 strains) from 14 pig farms in Japan from 2013 to 2016. Genetic analyses revealed that the haemagglutinin (HA) and neuraminidase (NA) genes of the 17 H1N1 and the HA gene of one H1N2, A/swine/Aichi/02/2016 (H1N2), SIVs belonged to the A(H1N1)pdm09 lineage. More importantly, all of the remaining six gene segments (i.e., PB1, PB1, PA, NP, M and NS) of the 24 SIVs, regardless of the HA and NA subtype, were also classified as belonging to the A(H1N1)pdm09 lineage. These results indicate that gene segments of A(H1N1)pdm09 lineage are widely distributed in SIVs circulating in Japanese pig populations In addition, the NA gene of A/swine/Aichi/02/2016 (H1N2) shared less than 88.5% nucleotide identity with that of the closest relative A/swine/Miyagi/5/2003 (H1N2), which was isolated in Japan in 2003. These results indicate the sustained circulation of classical H1N2-derived SIVs with remarkable diversity in the NA genes in Japanese pig populations. These findings highlight the necessity of both intensive biosecurity systems and active SIV surveillance in pig populations worldwide for both animal and public health.

Dental treatments, tooth extractions, and osteonecrosis of the jaw in Japanese patients with rheumatoid arthritis: results from the IORRA cohort study

This study aimed to evaluate dental treatments, tooth extractions, and osteonecrosis of the jaw (ONJ) in Japanese patients with rheumatoid arthritis (RA). Patients with RA enrolled in our cohort completed self-administered questionnaires, which included questions regarding their dental treatments, tooth extractions by dentists during the past 6 months, and past history of ONJ. The history of ONJ was validated with the patients' medical records. Logistic regression was used to determine the association of variables with dental treatments and tooth extractions during the past 6 months. Among 5695 Japanese patients with RA who responded to the questionnaires (mean age, 61.0 years; 85.6 % female), 2323 patients (40.8 %) and 378 patients (6.6 %) reported having had dental treatments and tooth extractions performed by a dentist within the past 6 months, respectively. In multivariate models, advanced age was significantly (P < 0.0001) associated with both dental treatments and tooth extractions during the prior 6-month period, and ever smoking was significantly (P = 0.023) correlated with tooth extractions during that time. Among patients who reported a history of ONJ, we confirmed five cases of ONJ with patient medical records. The prevalence of ONJ was 0.094 % among all RA patients and 0.26 % among female RA patients ≥65 years of age (n = 1888). Our data suggest that more than a few Japanese patients with RA have dental complications that require care by dentists, and that Japanese rheumatologists and dentists should cooperate to improve dental health in patients with RA.

[Calcium and bone metabolism across women's life stages. Osteoporosis in female patients with rheumatoid arthritis.]

Female patients with rheumatoid arthritis(RA)are at high risk for osteoporosis and fractures. In Japanese female patients with RA, age, disability, daily prednisolone dose, history of total knee replacement, and low bone mineral density are known to be risk factors for fractures, and more than 70% are reported to be vitamin D deficiency.

Activation of c-Jun N-terminal kinase by Akabane virus is required for apoptosis

Akabane virus (AKAV) belongs to the Simbu serogroup of the genus Orthobunyavirus in the family Bunyaviridae. It has been shown that AKAV induces apoptosis in mammalian cells. It is necessary to understand the signaling pathways involved in AKAV-induced apoptosis to further elucidate the molecular virology of AKAV. c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) are mediators of apoptosis; therefore, we investigated the roles of JNK and p38 MAPK cascades in AKAV-infected cells. We found that JNK and p38 MAPK as well as their downstream substrates, c-Jun and heat shock protein 27 (HSP27), were phosphorylated in response to AKAV infection. A JNK inhibitor (SP600125) inhibited AKAV-mediated apoptosis whereas a p38 MAPK inhibitor (SB203580) did not. We conclude that AKAV infection activates the JNK and p38 MAPK signaling pathways, and the JNK cascade plays a crucial role in AKAV-induced apoptosis in vitro.

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JNK and p38 MAPK were phosphorylated in response to Akabane virus infection.

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Downstream substrates, c-Jun and heat shock protein 27, were also phosphorylated by viral infection.

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JNK inhibitor (SP600125) inhibited AKAV-mediated apoptosis whereas a p38 MAPK inhibitor (SB203580) did not.

Generation of a sensitive TNFR2-specific murine assays system

Tumor necrosis factor (TNF)/TNF receptors (TNFR1/TNFR2) are considered to be potential drug targets to treat refractory diseases, including autoimmune diseases and malignant tumors. However, their specific functions, especially in the case of TNFR2, are poorly understood. In this study, we constructed a mouse TNFR2 (mTNFR2)-mediated biological assay system that shows no effects of mouse TNFR1 (mTNFR1) in order to screen mTNFR2-selective stimulating agents. Mouse TNFR1(-/-)R2(-/-) preadipocytes were transfected with the gene encoding the mTNFR2/mouse Fas (mFas) chimeric receptor in which the extracellular and transmembrane domains of mTNFR2 were fused to the intracellular domain of mFas. Our results demonstrated that this cell line exhibits highly sensitive mTNFR2-mediated cytotoxic effects. We propose that this mTNFR2-mediated biological assay system would be a useful tool to screen for mTNFR2-selective stimulating agents.

Patient preference for monthly bisphosphonate versus weekly bisphosphonate in a cluster-randomized, open-label, crossover trial: Minodroate Alendronate/Risedronate Trial in Osteoporosis (MARTO)

Minodronate is a potent nitrogen-containing bisphosphonate that can be administered according to a monthly (every 4 weeks) dosing regimen. A 6-month, cluster-randomized, open-label, multicenter, crossover trial was conducted to test the preference of Japanese patients with osteoporosis for monthly bisphosphonate versus weekly bisphosphonate. One hundred and forty-seven patients (postmenopausal women and men) with primary osteoporosis were recruited at eight outpatient clinics. The clinics were randomized into two groups according to the dosing protocol-monthly minodronate followed by weekly alendronate or risedronate for a total of 24 weeks, or weekly alendronate or risedronate followed by monthly minodronate for 24 weeks. Patient preference for either the monthly or weekly bisphosphonate regimen was evaluated using a preference questionnaire. One hundred and fifteen patients (78.2 %) who completed the trial were processed for the analyses. Significantly more patients preferred the monthly bisphosphonate regimen (65.2 %) than the weekly bisphosphonate regimen (15.7 %) (P = 0.007). 'Dosing schedule fits lifestyle better' was the most common reason given for the patient preference for both the monthly (32.0 %) and weekly bisphosphonate (33.3 %) regimens. Significantly more patients found the monthly bisphosphonate regimen to be more convenient (73.0 %) than the weekly bisphosphonate regimen (13.9 %) (P < 0.0001). The safety profiles of the two regimens were similar. The present trial demonstrated a strong patient preference for and the convenience of the monthly bisphosphonate regimen over the weekly bisphosphonate regimen in Japanese patients with osteoporosis.

Ten-year incidences of self-reported non-vertebral fractures in Japanese patients with rheumatoid arthritis: discrepancy between disease activity control and the incidence of non-vertebral fracture

Despite improvements in rheumatoid arthritis disease activity of in the past 10 years, the incidence of self-reported non-vertebral fractures did not decrease in our cohort of 9,987 patients. This study may indicate that osteoporosis treatment and non-vertebral fracture prevention remain important regardless of the rheumatoid arthritis disease activity.

INTRODUCTION

Although rheumatoid arthritis (RA) is a risk factor for osteoporosis and fractures, few studies have described the association between disease activity and the fracture incidence in patients with RA. This study aimed to investigate changes in the non-vertebral fracture incidence between 2001 and 2010 in our Institute of Rheumatology Rheumatoid Arthritis (IORRA) cohort.

METHODS

The IORRA is a prospective observational cohort study of Japanese RA patients. A total of 9,987 patients with RA were enrolled in this cohort from 2000 to 2010. The clinical parameter and non-vertebral fracture occurrence data were collected biannually through self-reported questionnaires. Incidences of self-reported non-vertebral fractures were also analyzed via standardization according to gender, age, and disease activity during each 2-year period.

RESULTS

From 2001 to 2010, the percentage of patients with 28-joint disease activity score remission increased from 7.8 to 39.7%, prednisolone intake decreased from 51.4 to 41.3%, and bisphosphonate intake increased from 5.0 to 23.4%. The non-vertebral fracture incidence rates were 24.6/1,000 person-years in 2001 and 35.5/1,000 person-years in 2010, with no apparent change even after standardization. The overall non-vertebral fracture incidence was significantly higher in the autumn/winter than in the spring/summer (p = 0.02).

CONCLUSION

Despite improvements in disease activity and functional disability, the non-vertebral fracture incidence exhibited no apparent change between 2001 and 2010 in our patients with RA. Osteoporosis treatment and non-vertebral fracture prevention remain important regardless of the disease control in patients with RA.

Survey of the utility of once-monthly bisphosphonate treatment for improvement of medication adherence in osteoporosis patients in Japan

Prescription of a bisphosphonate (BP) with monthly dosing has recently been approved in Japan. The value of this approach for improvement of medication adherence was investigated in patients undergoing drug therapy for osteoporosis. A questionnaire was distributed to patients receiving treatment for osteoporosis at 8 medical facilities (5 orthopedic, 2 gynecology, and one internal medicine). Responses were collected from 1,300 patients. After exclusion of those who missed an item on the questionnaire or took drugs other than oral drugs, responses from 1,151 patients were analyzed. The most frequently used drug for treatment of osteoporosis was a once-weekly BP. Of the 1,151 patients, 38.4 % reported forgetting to take their current drug. The most frequent concern was 'I cannot feel an effect', but 73.2 % answered 'I have no concerns'. Regarding the most appropriate dosing regimen for long-term treatment, 60.3 % selected once-weekly and 24 % selected once every 4 weeks. Based on a recommendation by a physician of a drug to be taken monthly, 32.5 % wanted to switch, 31.8 % were undecided, and 35.7 % wanted to continue with their current drug. The desire for a change was higher among patients currently taking a once-weekly BP (52.3 %) than among patients taking a daily BP (29.5 %) or a SERM (19.4 %). This survey revealed patients' preferences in osteoporosis drug therapy. It is important to select a drug for osteoporosis based on the efficacy and the drug regimen preferred by the individual patient.

[Epidemiology of bone and joint disease - the present and future - . Risk factors for fractures and treatment of osteoporosis in Japanese patients with rheumatoid arthritis]

Patients with rheumatoid arthritis (RA) are at increased risk for developing osteoporosis and fractures compared to controls. This risk is further increased since a majority of patients with RA also receive concomitant corticosteroids, which have been shown to induce osteoporosis and increase the risk of fractures. Glucocorticoids use and physical disability as well as low bone mineral density and older age are recognized as significant risk factors for fractures in patients with RA. This article reviews the epidemiology and treatment for osteoporosis in Japanese patients with RA.

Association between a C8orf13-BLK polymorphism and polymyositis/dermatomyositis in the Japanese population: an additive effect with STAT4 on disease susceptibility

Background

Accumulating evidence has shown that several non-HLA genes are involved in the susceptibility to polymyositis/dermatomyositis. This study aimed to investigate the involvement of C8orf13–BLK, one of the strongest candidate genes for autoimmune diseases, in susceptibility to polymyositis/dermatomyositis in the Japanese population. A possible gene–gene interaction between C8orf13–BLK and STAT4, which we recently showed to be associated with Japanese polymyositis/dermatomyositis, was also analyzed.

Methods

A single-nucleotide polymorphism in C8orf13–BLK (dbSNP ID: rs13277113) was investigated in the Japanese population using a TaqMan assay in 283 polymyositis patients, 194 dermatomyositis patients, and 656 control subjects.

Results

The C8orf13–BLK rs13277113A allele was associated with overall polymyositis/dermatomyositis (P<0.001, odds ratio [OR] 1.44, 95% confidence interval [CI] 1.19–1.73), as well as polymyositis (P = 0.011, OR 1.32, 95% CI 1.06–1.64) and dermatomyositis (P<0.001, OR 1.64, 95% CI 1.26–2.12). No association was observed between the C8orf13–BLK rs13277113A allele and either interstitial lung disease or anti-Jo-1 antibody positivity. The C8orf13–BLK rs13277113 A and STAT4 rs7574865 T alleles had an additive effect on polymyositis/dermatomyositis susceptibility. The strongest association was observed in dermatomyositis, with an OR of 3.07 (95% CI; 1.57–6.02) for the carriers of four risk alleles at the two SNP sites, namely, rs1327713 and rs7574865.

Conclusions

This study established C8orf13–BLK as a new genetic susceptibility factor for polymyositis/dermatomyositis. Both C8orf13–BLK and STAT4 exert additive effects on disease susceptibility. These observations suggested that C8orf13–BLK, in combination with STAT4, plays a pivotal role in creating genetic susceptibility to polymyositis/dermatomyositis in Japanese individuals.