Advances in Idiopathic Inflammatory Myopathies Classification: Paving the Way for Personalized Management

Since the Bohan and Peter criteria were established in 1975,1, 2 the field of idiopathic inflammatory myopathies (IIM) has undergone significant developments in diagnostic and classification methodologies.3, 4 IIM are known for the diversity of their clinical presentations and treatment responses, and they continue to pose challenges for clinicians and researchers in terms of accurate diagnosis and the quest for tailored therapeutic strategies.5

Accurately diagnosing IIM is complex due to overlapping clinical features, variations in disease progression, and extramuscular manifestations. This situation has resulted in comprehensive approaches being applied to patient evaluations, involving clinical criteria, histopathological findings, and serological markers. However, despite these efforts, the path from clinical suspicion to a definitive diagnosis remains challenging.

One of the notable recent changes in the IIM classification is the division of cases into four primary diseases: dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASS), and sporadic inclusion-body myositis.4 This updated classification is more comprehensive and precise than its predecessors. It offers valuable insights into the distinct characteristics of each IIM case, including the age at onset, serum creatine kinase (CK) levels, and muscle imaging findings, which significantly contribute to the diagnosis and treatment of IIM. A full understanding of the underlying pathogenic mechanisms is increasingly recognized as a prerequisite for advancing patient care, and this new classification unquestionably aids clinicians in this pursuit.

In this context, a study reported in the current issue of the Journal of Clinical Neurology supports the value of refining this classification. The research conducted by Park et al.6 on the clinicopathological reclassification of IIM using advanced serological tests enhances our comprehension of the disease and opens avenues for new therapeutic insights. The study was grounded on clinical, histopathological, and serological data, and applied the new IIM classification criteria to reclassify 71 IIM cases into 4 main categories: IMNM, DM, polymyositis (PM), and nonspecific myositis. Furthermore, it categorizes cases into overlap myositis and ASS based on serological results. The study also investigated the correlation between myositis-specific antibodies and the updated clinicopathological classification. By elucidating the connection between myositis-specific antibodies and the clinicopathological classification, the study has refined diagnostic criteria for conditions such as PM to make them easier to distinguish from other muscular disorders. By anchoring the classification in the pathogenesis of IIM, the study paves the way for more-precise management and a deeper comprehension of this disease.

Another recent study focusing on anti-3-hydroxy-3-methylglutaryl-coA reductase (HMGCR) myopathy make us sure the value of refining the classification of IIM.7 Those authors analyzed anti-HMGCR antibodies in a diverse sample to reveal unique clinical characteristics of Korean patients with anti-HMGCR myopathy, noting a 17% prevalence among patients with inflammatory myopathy. These findings align with global patterns of subacute progressive proximal muscle weakness and elevated serum CK levels, predominantly affecting females. That study has provided unique insights into the Korean population, highlighting the frequent coexistence of other myositis-specific antibodies, higher titers of anti-HMGCR antibodies in statin-naïve patients, and a decrease in antibody levels following immunotherapy in both statin-exposed and naïve groups. These findings necessitate a reassessment of diagnostic and treatment frameworks, which will require further large-scale, demographic-specific research.

These two recent studies underscore the need for precision and clarity in understanding and managing IIM. Their contributions call for a more-precise categorization of IIM based on molecular and immunopathological criteria. Based on the recently highlighted articles above, it becomes evident that we should continue to direct our efforts toward creating robust and scientifically justified classification criteria for IIM, with the aim of paving the way for personalized treatment modalities aligned with the unique characteristics of IIM, thereby ultimately enhancing the quality of patient care.