A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis

Nishigaichi, Akira; Amano, Yu; Sada, Ryuichi Minoda; Miyake, Hirofumi; Maruyama, Wataru; Tagawa, Shunsuke; Akebo, Hiroyuki; Hatta, Kazuhiro; Nishino, Ichizo

doi:https://doi.org/10.1007/s11606-024-09012-1

A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis

Nishigaichi, Akira; Amano, Yu; Sada, Ryuichi Minoda et al.

Journal of General Internal Medicine, 2024, 40(2), 479-484

Number of Access:517（2025-08-14 05:02 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/98223

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Title	A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis
Creator	CreatorName Nishigaichi, Akira
	CreatorName Amano, Yu
	NRID 1000040961230 1000040961230 ORCID 0000-0002-1455-6822 0000-0002-1455-6822 researchmap permalink sadametal sadametal Scopus Author ID 59319135000 59319135000 CreatorName Sada, Ryuichi Minoda
	CreatorName Miyake, Hirofumi
	CreatorName Maruyama, Wataru
	CreatorName Tagawa, Shunsuke
	CreatorName Akebo, Hiroyuki
	CreatorName Hatta, Kazuhiro
	NRID 1000000332388 1000000332388 CreatorName Nishino, Ichizo
Subject	Myositis
	Mi-2 antibodies
	amyloidosis
Description	This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s11606-024-09012-1.
Abstract	Amyloidosis is characterized by the deposition of abnormal amyloid protein in variable organs, leading to organ failures.1 Amyloid myopathy is one of the rare complications of systemic amyloidosis. It manifests as proximal muscle weakness and creatine kinase elevation, resembling idiopathic inflammatory myopathies (IIMs).2,3,4,5,6 In contrast, IIMs are autoimmune diseases characterized by inflammation in muscles, and dermatomyositis is one of the subgroups of IIMs. To date, at least seven serum markers of dermatomyositis, known as myositis-specific antibodies (MSAs), have been identified.7,8 They are known to exhibit high specificity for dermatomyositis, and anti-Mi-2 antibody is one of them.9,10 Since the treatment of dermatomyositis is immunosuppressive drugs, including glucocorticoids, whereas the treatment of AL amyloidosis requires chemotherapy, it is important to make the correct diagnosis of amyloid myopathy without misdiagnosing dermatomyositis.We encountered a case diagnosed with amyloid myopathy through muscle biopsy, despite testing positive for the anti-Mi-2 antibody. This case highlights the potential for false-positive results in myositis-specific antibody tests and emphasizes the importance of advancing clinical reasoning beyond sole reliance on antibody testing.Informed consent was obtained from the patient for publication of the report and associated images.
Publisher	Springer
Source Title	Journal of General Internal Medicine
Volume (Issue)	40(2)
Page	479-484
Date of Issued	2024-09-09
Language	English
Handle URL	https://hdl.handle.net/11094/98223
PISSN	08848734
eISSN	15251497
Relation.isVersionOf	DOI (Publisher Version) https://doi.org/10.1007/s11606-024-09012-1
Access Rights	embargoed access
CopyRight	The full-text file will be made open to the public on 9 September 2025 in accordance with the publisher's policy.
oaire:version	Accepted Manuscript
Category	学術雑誌論文 Journal Article

Resource Type	journal article
Local Type	Journal Article
DCTERMS.bibliographicCitation	Journal of General Internal Medicine. 2024, 40(2), p. 479-484
DC.title	A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis
DC.creator	Nishigaichi, Akira
	Amano, Yu
	Sada, Ryuichi Minoda
	Miyake, Hirofumi
	Maruyama, Wataru
	Tagawa, Shunsuke
	Akebo, Hiroyuki
	Hatta, Kazuhiro
	Nishino, Ichizo
DC.publisher	Springer
DC.language' scheme='DCTERMS.RFC1766	English
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2024-09-09
DC.identifier	https://doi.org/10.1007/s11606-024-09012-1
DC.subject	Myositis
	Mi-2 antibodies
	amyloidosis
DC.description	This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s11606-024-09012-1.
DCTERMS.abstract	Amyloidosis is characterized by the deposition of abnormal amyloid protein in variable organs, leading to organ failures.1 Amyloid myopathy is one of the rare complications of systemic amyloidosis. It manifests as proximal muscle weakness and creatine kinase elevation, resembling idiopathic inflammatory myopathies (IIMs).2,3,4,5,6 In contrast, IIMs are autoimmune diseases characterized by inflammation in muscles, and dermatomyositis is one of the subgroups of IIMs. To date, at least seven serum markers of dermatomyositis, known as myositis-specific antibodies (MSAs), have been identified.7,8 They are known to exhibit high specificity for dermatomyositis, and anti-Mi-2 antibody is one of them.9,10 Since the treatment of dermatomyositis is immunosuppressive drugs, including glucocorticoids, whereas the treatment of AL amyloidosis requires chemotherapy, it is important to make the correct diagnosis of amyloid myopathy without misdiagnosing dermatomyositis.We encountered a case diagnosed with amyloid myopathy through muscle biopsy, despite testing positive for the anti-Mi-2 antibody. This case highlights the potential for false-positive results in myositis-specific antibody tests and emphasizes the importance of advancing clinical reasoning beyond sole reliance on antibody testing.Informed consent was obtained from the patient for publication of the report and associated images.
DC.rights	The full-text file will be made open to the public on 9 September 2025 in accordance with the publisher's policy.
DC.format	98223
citation_title	A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis
citation_author	Nishigaichi, Akira
	Amano, Yu
	Sada, Ryuichi Minoda
	Miyake, Hirofumi
	Maruyama, Wataru
	Tagawa, Shunsuke
	Akebo, Hiroyuki
	Hatta, Kazuhiro
	Nishino, Ichizo
citation_publisher	Springer
citation_language	English
citation_date	2024-09-09
citation_journal_title	Journal of General Internal Medicine
citation_volume	40
citation_issue	2
citation_firstpage	479
citation_lastpage	484
citation_doi	https://doi.org/10.1007/s11606-024-09012-1
citation_public_url	https://hdl.handle.net/11094/98223

A Case of Amyloid Myopathy Mimicking Anti-Mi-2 Antibody-Positive Myositis

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