Clinical and Radiological Features of Korean Patients With Anti-HMGCR Myopathy

Management of immune-mediated necrotizing myopathy

The immune-mediated necrotizing myopathies (IMNM) are autoimmune myositides clinically characterized by proximal predominant weakness and elevated creatine kinase (CK). They may be associated with autoantibodies (anti-HMGCR, anti-SRP), triggered by statin use (e.g., anti-HMGCR myopathy), associated with cancer, or may be idiopathic. Immunotherapy is required to improve strength and decrease the CK level, but no therapies are currently approved by the U.S. Food and Drug Administration for the treatment of IMNM. The optimal treatment strategy for IMNM is currently unknown and wide practice variation exists in the management of this condition. However, observational studies and expert opinion suggest that certain therapies may be more effective for the different serological subtypes of IMNM. HMGCR IMNM often responds favorably to intravenous immunoglobulin (IVIG) even as monotherapy. Signal recognition peptide and seronegative IMNM typically require combination immunotherapy, most often consisting of an oral immunosuppressant, corticosteroids, and IVIG or rituximab. Patients often remain on immunotherapy for years and relapse is common during tapering of immunotherapy. Further studies are needed to guide the optimal management of these patients.

Immune-Mediated Necrotizing Myopathies: Current Landscape

PURPOSE OF REVIEW

Immune-mediated necrotizing myopathy (IMNM), characterized by acute or subacute onset, severe weakness, and elevated creatine kinase levels, poses diagnostic and therapeutic challenges. This article provides a succinct overview of IMNM, including clinical features, diagnostic strategies, and treatment approaches.

RECENT FINDINGS

Recent insights highlight the different clinical presentations and therapeutic options of IMNM stratified by autoantibody positivity and type. Additionally, recent findings call into question the reported link between statin use and IMNM. This review synthesizes current knowledge on IMNM, emphasizing its distinct clinical features and challenging management. The evolving understanding of IMNM underscores the need for a comprehensive diagnostic approach that utilizes a growing range of modalities. Early and aggressive immunomodulatory therapy remains pivotal. Ongoing research aims to refine diagnostic tools and therapeutic interventions for this challenging muscle disorder, underscoring the importance of advancing our understanding to enhance patient outcomes.

Anti-HMGCR immune-mediated necrotising myopathy: Addressing the remaining issues

The discovery of autoantibodies directed against the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) enzyme has defined a sub-set of immune-mediated necrotising myopathy (IMNM) which is strongly associated with exposure to statin medications. Although understanding of anti-HMGCR IMNM has grown considerably with the reporting of multiple cohorts in North America, Europe, Asia and Oceania, there remain many unanswered questions. The true incidence of anti-HMGCR IMNM is not known and heterogeneity of phenotype and treatment response within this autoantibody sub-group is being increasingly recognised. Statin-naïve adults and juvenile patients with anti-HMGCR potentially share characteristics distinct from statin-exposed patients, alluding to unique pathogenesis. Conflicting data exists on whether malignancies are associated with anti-HMGCR and further clarification is required to determine the degree of cancer screening required. Treatment approaches to anti-HMGCR IMNM are heterogeneous but generally highlight the efficacy of intravenous immunoglobulin. Even with multimodal immunosuppression, patients with anti-HMGCR remain prone to relapse, with younger patients generally manifesting more refractory disease. In this Review, we aim to summarise the current literature on anti-HMGCR and discuss the remaining issues.