J Pathol Transl Med.  2024 Jul;58(4):174-181. 10.4132/jptm.2024.05.02.

Immunohistochemical expression in idiopathic inflammatory myopathies at a single center in Vietnam

• Ngo DQ
• Le ST
• Phan KHP
• Doan TTP
• Nguyen LNK
• Dang MH
• Ly TT
• Phan TDA

• KMID: 2557757
• DOI: http://doi.org/10.4132/jptm.2024.05.02

Abstract

Background
The identification of idiopathic inflammatory myopathies (IIMs) requires a comprehensive analysis involving clinical manifestations and histological findings. This study aims to provide insights into the histopathological and immunohistochemical aspects of IIMs.
Methods
This retrospective case series involved 56 patients diagnosed with IIMs at the Department of Pathology, University of Medicine and Pharmacy at Ho Chi Minh City, from 2019 to 2023. The histology and immunohistochemical expression of HLA-ABC, HLA-DR, C5b-9, Mx1/2/3, and p62 were detected.
Results
We examined six categories of inflammatory myopathy, including immunemediated necrotizing myopathy (58.9%), dermatomyositis (DM; 23.2%), overlap myositis (8.9%), antisynthetase syndrome (5.4%), inclusion body myositis (IBM; 1.8%), and polymyositis (1.8%). The average age of the patients was 49.7 ± 16.1 years, with a female-to-male ratio of 3:1. Inflammatory cell infiltration in the endomysium was present in 62.5% of cases, perifascicular atrophy was found in 17.8%, and fiber necrosis was observed in 42 cases (75.0%). Rimmed vacuoles were present in 100% of cases in the IBM group. Immunohistochemistry showed the following positivity rates: HLA-ABC (89.2%), HLA-DR (19.6%), C5b-9 (57.1%), and Mx1/2/3 (10.7%). Mx1/2/3 expression was high in DM cases. p62 vacuole deposits were noted in the IBM case. The combination of membrane attack complex and major histocompatibility complex I helped detect IIMs in 96% of cases.
Conclusions
The diagnosis of IIMs and their subtypes should be based on clinical features and histopathological characteristics. Immunohistochemistry plays a crucial role in the diagnosis and differentiation of these subgroups.

Keyword

Idiopathic inflammatory myopathies; immunohistochemistry; HLA-ABC; HLA-DR; C5b-9; Mx1/2/3; p62

Figure

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  Fig. 1. (A) Infiltration of mononuclear inflammatory cells in the endomysial region. (B) Myofiber necrosis and myophagocytosis indicated by asterisks. (C) Infiltration of mononuclear inflammatory cells in the interfascicular region and perivascular area. (D) Perifascicular atrophy. (E) Rimmed vacuole. (F) Rimmed vacuole indicated by asterisks (modified Gomori trichrome).

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  Fig. 2. (A) Membranous and cytoplasmic MHC-1 expression. (B) Membranous and cytoplasmic membrane attack complex (MAC) expression. (C) Deposits of MAC on endomysial capillaries. (D) Mx1/2/3 expression on perifasicular atrophy. (E) Cytoplasmic p62 expression. (F) Deposits of p62 in rimmed vacuoles indicated by asterisks.

Reference

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