Autoimmune myositis had been classified into dermatomyositis and polymyositis based mainly upon the presence or absence of skin rash. However, recent advances in muscle pathology and serology have revealed the presence of at least three independent subtypes in juvenile autoimmune myositis : dermatomyositis, immune-mediated necrotizing myopathy, and antisynthetase syndrome, each of which has distinct pathogenesis while the existence of pathologically-defined polymyositis has become questionable. Most of the pediatric patients who are clinically diagnosed with polymyositis actually have either immune-mediated necrotizing myopathy, antisynthetase syndrome, or dermatomyositis sine dermatitis.

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Epigenetics is the study of changes in gene expression or cellular expression systems that are inherited after cell division without DNA sequence changes. In this article, we review the epigenetic regulation of gene expression in the two major pediatric rheumatic diseases, juvenile idiopathic arthritis and systemic lupus erythematosus, and their potential as biomarkers and therapeutic targets.

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Type I interferonopathy is a group of Mendelian inflammatory disorders where chronic and autonomous enhancement of type I interferon （IFN） production is central to the pathogenesis. In these disorders, upregulation of type I IFN signaling can occur due to abnormal accumulation of endogenous nucleic acids, inappropriate stimulation or defective negative regulation of type I IFN signaling pathway, and defective proteasome activities. Upregulated type I IFN signaling has also been identified in autoimmune diseases including SLE and dermatomyositis, suggesting strong association between IFN and development of these diseases. Conversely, some type I interferonopathies develop similar symptoms as SLE and other autoimmune diseases, suggesting these non-genetic diseases have the same or similar underlying mechanism of enhanced type I IFN signaling. In this review, we focus on molecular mechanisms leading to activation of type I IFN signaling in the pathogenesis of interferonopathies and autoimmune diseases.

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Coronavirus disease 2019 （COVID-19） is the disease caused by severe acute respiratory syndrome coronavirus 2 （SARS-CoV-2）, which appeared in Wuhan, China, in December 2019 and has continued to spread rapidly around the world. Although the majority of COVID-19 in children are mild, there are many important unanswered questions. And the influence of COVID-19 against pediatric rheumatic diseases is also limited. On the other hand, after COVID-19, a new disease with multisystem inflammatory syndrome in children （MIS-C/PIMS） was reported. In this article, this review highlights the current findings on COVID-19, pediatric rheumatic diseases and medical care.

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The 2020 edition of the Guidance for the Initial Clinical Practice of Pediatric Noninfectious Uveitis was published for the first time in Japan. This was due to the lack of awareness of this rare diseases and the lack of established treatment strategies in spite of intractable conditions. Therefore, pediatric rheumatologists and ophthalmologists worked together to standardize optimal treatment and management, and to ensure strong collaboration between pediatricians and ophthalmologists. Pediatric noninfectious uveitis has few subjective symptoms at onset, and it has already progressed to some extent at the time of diagnosis, and there are many cases with complications. It may also appear as one symptom of systemic disease or require systemic treatment, that is why collaboration is important. This article reviews the current situation of pediatric non-infectious uveitis based on overseas and domestic epidemiological studies and other literature reports, and explains the reason why 'guidance is necessary'. In addition, we will explain the matters described in the manual and explain the essences and cautions on how to use them. It is hoped that the use of this guidance will lead to the widespread recognition of non-infectious uveitis patients in children, the expansion of new diagnostic tools, and therapeutic drugs, and the early diagnosis and improvement of prognosis.

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【Objective】To clarify the present situations of adult patients with pediatric rheumatic diseases as to the hospital visits, higher education, employment, marriage, and pregnancy. 【Methods】 Questionnaires were sent to patients over 20 years old as of 2019 who had admitted or seen multiple times to our department. The data were compared with the official database of general population in the same age group （nationwide survey） and with the previous survey in 2006 （previous survey 2006）. 【Results】 114 patients responded to the survey（ response rate 45.8％）. [Hospital visit] The department the patients visited was internal medicine（ 47.9％）, rheumatology（ 33.0％）, and pediatrics（ 21.3％）. The incidence of patients visited to Pediatrics significantly decreased compared with the previous survey 2006. [Higher education] 42.3％ of the respondents went on to university, which increased from the previous survey 2006. [Job] The highest rate of industry type was medical welfare（ 39.7％）, which was significantly higher than that of normal population with the same age group. [Marriage] Marriage rate was 35.4％, the same as nationwide survey and previous survey 2006. [Pregnancy] 66.7％ of pregnant women changed their treatment around their gestation, and 33.3％ experienced a miscarriage, and 19.0％ received treatment for infertility. 【 Conclusion】 The rate of transition to adult medicine increased and their life events were less hindered by disease than that of previous survey 2006.

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ReA is a sterile arthritis typically affecting lower limbs, following extra-articular infections such as gastrointestinal and urogenital infection. It has been suggested that HLA-B27-mediated immune response and interactions between host cells and disease-triggering pathogens are crucial for pathophysiology of ReA. However, reports of Japanese children with ReA are rare because of the low positivity for HLA-B27 in Japanese. Here we report a 13-year-old Japanese girl who was admitted to our hospital because of the arthritis of her right wrist and elbow. She had fever, abdominal pain and diarrhea 11 days prior to admission. Her fever persisted despite antibiotics therapy as well as non-steroidal anti-inflammatory drugs, and arthritis became migratory from her upper limbs to lower limbs. She was diagnosed with ReA because Yersinia enterocolitica was detected by stool culture. After prednisolone was started, her arthritis gradually were improved. Subsequently, the positivity of HLA-B27 and increase in titer of serum antibody for Yersinia enterocolitica were detected. Gastrointestinal infection is relatively more frequent than urogenital infection as preceding infection of pediatric ReA. Our patient was diagnosed with ReA because of coincidental detection of Yersinia enterocolitica in stool culture. However, detection of disease-triggering pathogens by culture tests could be difficult in many cases. Therefore, pathogen identification by antibody measurements, and HLA-B27 serotyping should be performed to diagnose ReA.

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【Background】Although the incidence of pulmonary thromboembolism caused by renal vein thromboembolism is extremely low in pediatric SLE, it may be a fatal complication regardless of treatment. Lp（a） is well-recognized lipoprotein related to developing venous thromboembolism. We evaluated the clinical significance of elevated Lp（a） based on our case which developed thromboembolism. 【Case presentation】The case was a 14-year-old SLE girl who had been being follow-up at our department and was hospitalized for a complaint of right flank pain. She developed SLE at the age of six and had a history of lupus nephritis class II（ ISN/RPS） and recurrent lupus enteritis. It was already confirmed that the levels of Lp（a） were more than 30mg/dL prior to the onset of thromboembolism. Laboratory findings included elevated D-dimer and thrombocytopenia, as well as hypoalbuminemia and proteinuria due to nephrotic syndrome, but she had no laboratory findings suggestive of antiphospholipid antibody syndrome. Chest/abdominal contrast CT examination revealed a contrast defect due to thromboembolism in the left pulmonary artery and right renal vein. The thrombolysis for emboli was performed for five months and the thromboembolism did not recur following the completion of therapy. 【 Conclusions】Although it is hard to associate a causality based on our case report, elevated Lp（a） as a genetic predisposition to hemostasis may be associated with renal vein thromboembolism. It was suggested that it is important to check the Lp（a） level as a predictive factor for renal vein thromboembolism and to be careful follow-up the SLE patients with increased Lp（a）.

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