A 68-year-old woman presented with a one-month history of polyarthritis and fever, followed by myalgia and muscle weakness involving the proximal limbs, neck, trunk, and distal upper extremities. Myositis was suspected based on an elevated serum CK level. Chest CT revealed interstitial pneumonia. Commercial laboratory tests, including ELISA and immunoblot, were positive for anti-Ro-52 antibodies but negative for anti-aminoacyl transfer RNA synthetase (ARS) antibodies. However, muscle pathology revealed perifascicular necrosis and perimysial pathology, strongly suggesting anti-synthetase syndrome (ASS). Further investigation using RNA immunoprecipitation (RIP) assay identified positive anti-EJ antibodies, leading to the diagnosis of ASS. In addition, anti-Ku and anti-U1 RNP antibodies were co-positive. These findings highlight that, even when ELISA and immunoblot were negative for specific antibodies, RIP assay is necessary when ASS is suspected based on myopathologic findings.
"},{"@language":"ja","@value":"68歳女性．多関節炎，発熱，筋痛，四肢近位・頸部体幹・上肢遠位の筋力低下を認めた．高CK血症より筋炎が疑われ，間質性肺炎を伴った．検査会社に依頼可能なELISA法・immunoblot法では抗アミノアシルtRNA合成酵素（aminoacyl transfer RNA synthetase: ARS）抗体は陰性だったが，筋病理でのperifascicular necrosisとperimysial pathologyより抗合成酵素症候群を強く疑い，RNA免疫沈降法で再測定し，抗EJ抗体が陽性であり診断に至った．抗Ku抗体，抗U1-RNP抗体，抗Ro-52抗体も共陽性だった．検査会社に依頼可能な検査で陰性であっても，筋病理所見などから本疾患を疑った際にはRNA免疫沈降法での抗体測定が必要である．
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Hospital"},{"@language":"ja","@value":"東京都立神経病院脳神経内科"}]},{"@id":"https://cir.nii.ac.jp/crid/1410022167032242560","@type":"Researcher","foaf:name":[{"@language":"en","@value":"Adachi Tadashi"},{"@language":"ja","@value":"足立 正"}],"jpcoar:affiliationName":[{"@language":"en","@value":"Division of Neuropathology, Department of Brain and Neurosciences, Faculty of Medicine, Tottori University"},{"@language":"ja","@value":"鳥取大学医学部脳神経医科学講座神経病理学分野"}]},{"@id":"https://cir.nii.ac.jp/crid/1410022167032242561","@type":"Researcher","foaf:name":[{"@language":"ja","@value":"鈴木 重明"},{"@language":"en","@value":"Suzuki Shigeakai"}],"jpcoar:affiliationName":[{"@language":"en","@value":"Department of Neurology, Keio University School of Medicine"},{"@language":"ja","@value":"慶應義塾大学医学部神経内科"}]},{"@id":"https://cir.nii.ac.jp/crid/1410022167032242565","@type":"Researcher","foaf:name":[{"@language":"ja","@value":"西野 一三"},{"@language":"en","@value":"Nishino Ichizo"}],"jpcoar:affiliationName":[{"@language":"en","@value":"Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry"},{"@language":"ja","@value":"国立精神・神経医療研究センター神経研究所疾病研究第一部"}]},{"@id":"https://cir.nii.ac.jp/crid/1410022167032242564","@type":"Researcher","foaf:name":[{"@language":"ja","@value":"花島 律子"},{"@language":"en","@value":"Hanajima Ritsuko"}],"jpcoar:affiliationName":[{"@language":"en","@value":"Division of Neurology, Department of Brain and Neurosciences, Faculty of Medicine, Tottori University"},{"@language":"ja","@value":"鳥取大学医学部脳神経医科学講座脳神経内科学分野"}]}],"publication":{"publicationIdentifier":[{"@type":"PISSN","@value":"0009918X"},{"@type":"EISSN","@value":"18820654"}],"prism:publicationName":[{"@language":"en","@value":"Rinsho Shinkeigaku"},{"@language":"ja","@value":"臨床神経学"},{"@language":"en","@value":"Rinsho Shinkeigaku"},{"@language":"ja","@value":"臨床神経学"}],"dc:publisher":[{"@language":"en","@value":"Societas Neurologica Japonica"},{"@language":"ja","@value":"日本神経学会"}],"prism:publicationDate":"2025","prism:volume":"65","prism:number":"3","prism:startingPage":"211","prism:endingPage":"217"},"reviewed":"false","url":[{"@id":"https://www.jstage.jst.go.jp/article/clinicalneurol/65/3/65_cn-002009/_pdf"},{"@id":"https://search.jamas.or.jp/link/ui/2025277915"}],"availableAt":"2025","foaf:topic":[{"@id":"https://cir.nii.ac.jp/all?q=%E6%8A%97ARS%E6%8A%97%E4%BD%93","dc:title":"抗ARS抗体"},{"@id":"https://cir.nii.ac.jp/all?q=%E6%8A%97EJ%E6%8A%97%E4%BD%93","dc:title":"抗EJ抗体"},{"@id":"https://cir.nii.ac.jp/all?q=%E6%8A%97Ku%E6%8A%97%E4%BD%93","dc:title":"抗Ku抗体"},{"@id":"https://cir.nii.ac.jp/all?q=RNA%E5%85%8D%E7%96%AB%E6%B2%88%E9%99%8D%E6%B3%95","dc:title":"RNA免疫沈降法"},{"@id":"https://cir.nii.ac.jp/all?q=%E7%82%8E%E7%97%87%E6%80%A7%E7%AD%8B%E7%96%BE%E6%82%A3","dc:title":"炎症性筋疾患"},{"@id":"https://cir.nii.ac.jp/all?q=anti-ARS%20antibody","dc:title":"anti-ARS 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