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Review
. 2022 Oct 13:13:1019972.
doi: 10.3389/fimmu.2022.1019972. eCollection 2022.

Anti-SRP immune-mediated necrotizing myopathy: A critical review of current concepts

Xue Ma  1 , Bi-Tao Bu  2
Affiliations
Review

Anti-SRP immune-mediated necrotizing myopathy: A critical review of current concepts

Xue Ma et al. Front Immunol. .

Abstract

Purpose of review: This review aims to describe clinical and histological features, treatment, and prognosis in patients with anti-signal recognition particle (SRP) autoantibodies positive immune-mediated necrotizing myopathy (SRP-IMNM) based on previous findings.

Previous findings: Anti-SRP autoantibodies are specific in IMNM. Humoral autoimmune and inflammatory responses are the main autoimmune characteristics of SRP-IMNM. SRP-IMNM is clinically characterized by acute or subacute, moderately severe, symmetrical proximal weakness. Younger patients with SRP-IMNM tend to have more severe clinical symptoms. Patients with SRP-IMNM may be vulnerable to cardiac involvement, which ought to be regularly monitored and cardiac magnetic resonance imaging is the recommended detection method. The pathological features of SRP-IMNM are patchy or diffuse myonecrosis and myoregeneration accompanied by a paucity of inflammatory infiltrates. Endoplasmic reticulum stress-induced autophagy pathway and necroptosis are activated in skeletal muscle of SRP-IMNM. Treatment of refractory SRP-IMNM encounters resistance and warrants further investigation.

Summary: Anti-SRP autoantibodies define a unique population of IMNM patients. The immune and non-immune pathophysiological mechanisms are involved in SRP-IMNM.

Keywords: ER stress; anti-SRP autoantibodies; cardiac involvement; immune-mediated necrotizing myopathy; refractory.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Examples of a thigh and lower leg MRI in SRP-IMNM. (A), a T2-weighted image shows obvious edema in the adductor magnus, gracilis, and sartorius of the thigh (red arrow) and fascial edema (blue arrowhead). (B), a T1-weighted image reveals evident muscle atrophy and fatty replacement in the posterior muscles of the thigh (blue arrow). These pictures are cited from our previous study (7).
Figure 2
Figure 2
Pathological characteristics of muscle biopsy in SRP-IMNM. (A), dystrophin combined with eosin staining reveals necrosis myofibers (asterisk). (B), immunohistochemical staining of Neural Cell Adhesion Molecule1 (NCAM1)/CD56 shows scattered myofiber regeneration. Inflammatory cell analysis demonstrates scattered or focal CD68+ macrophage infiltration and myophagocytosis (C), scattered CD4+ (D) and CD8+ T lymphocyte (E), and a few CD20+B lymphocytes (F). Magnification (A-F): 200x. These pictures are cited from our previous study (7, 63).
See this image and copyright information in PMC

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