Idiopathic Inflammatory Myopathies Classification

Tushar Trivedi^*
*Correspondence: Tushar Trivedi, Department of Neurology, Palmetto Health Hospital, United States, Email:

Keywords

• Immune checkpoint inhibitor • Inclusion body myositis• Antisynthetase syndrome

Introduction

Idiopathic inflammatory myopathies (IIM), also known as autoimmune myositis, are a rare group of muscle disorders associated with autoimmunity that have a heterogeneous but highly specific spectrum of muscle and extramuscular involvement. Historically, IIM has been divided into three major subgroups, including polymyositis, dermatomyositis, and inclusion body myositis (IBM) primarily because of their clinical or pathological features, or both in combination. The discovery of myositis-specific antibodies (MSA) and the increasing evidence of their association with relatively specific clinic pathological features along with the transcriptomic findings have gradually changed the trend of IIM classification over the past four decades towards clinical-eropathological criteria, which IIM divide subgroups into four main categories: dermatomyositis, IBM, immune-mediated necrotizing myopathy (IMNM), and recently proposed as a separate entity anti-synthetase syndrome (ASS), while the existence of polymyositis as a separate entity h This review summarizes and comments on the latest findings on the classification of main subgroups of the IIM.

Dermatomyositis

In the 1975 Bohan and Peter Classification, patients with myositis were clinically divided into dermatomyositis and polymyositis by the presence of a typical rash, including a description associated with heliotrope rash, periorbital edema, Gottron's papules, Gottron’s sign, V. the same sign and the scarf sign only for dermatomyositis. Interestingly, their pathological criteria did not separate dermatomyositis from polymyositis as they allowed peripascicular atrophy (AFP) to be present in both entities. Some of the later classifications were also clinically oriented with variations of expert criteria. The clinic pathological classification of dermatomyositis was introduced in 1991 by Dalakas and later by the 119th International Classification Workshop for Idiopathic Inflammatory Myopathies of the European Neuromuscular Center (ENMC). 2003 (ENMCIIM 2003). Symmetrical limb belt type Muscle weakness and rash typical of dermatomyositis and require AFP as a specific criterion for the diagnosis of "definitive" dermatomyositis.

Anti-Synthetase Syndrome

ASS is a serologically based entity defined by the presence of one of the following autoantibodies against aminoacyltransfer RNA synthetase (antisynthetase): antiJo1 (histidyl), antiPL7 (threonyl), antiPL12 (alanyl) , antiEJ (Glycyl), antiOJ (Isoleucyl), antiKS (Asparaginyl), antiHa (Tyrosyl) and antiZo (Phenylalanyl) clinically accompanied by various combinations of myositis, interstitial lung disease (ILD), arthritis/arthralgia, mechanic hands, Raynaud and fever. it is rarely associated with cancer and rarely occurs in children. The clinical findings and clinical courses of ASA are varied in the reports. AntiJo1 has been reported to show a trend towards heavier and more exclusive muscle involvement, while AntiPL7 and AntiPL12 show a trend towards heavier and more exclusive lung involvement. However, a recent large retrospective study of 828 patients from the American and European Antisynthetase Network Collaborative Syndrome Cohorte (AENEAS) showed great similarity in the clinical results and course of these antibodies, although muscle involvement was less common in anti PL12.

Immune-Mediated Necrotizing Myopathy

The current classification of the IMNM, which was published in 2016 from 224th three subgroups according to positive antibodies: anti-signal recognition particles (SRP) IMNM, anti-3-hydroxy-3-methylgluarylcoenzyme- A-reductase (HMGCR) and seronegative IMNM; MNMI can affect people of different ages. In children, the disease can progress slowly, mimicking muscular dystrophy; the earliest age of onset of MNMI is 10 months old in a patient with positive antiHMGCR. Among the three subgroups, anti-SRP-IMNM is associated with more severe muscle involvement and may be associated with an increased risk of cardiac involvement and PID.

Inclusion Body Myositis

The first IBM classification by Griggs et al. In 1995 it was mainly based on pathologies; it allowed IBM to diagnose without the need for clinical or laboratory data when the muscle biopsy already met all of the pathological criteria. The clinic pathological classification of IBM was then used duri ng the 188 diagnostic flexibilities compared to the classification by Griggs et al

Conclusion

IIM is suggestively labeled into 4 principal subgroups: dermatomyositis, ASS, IMNM, and IBM. Most of the classifications are clinicoseropathological orientated that scientific and serological criteria play principal parts. Transcriptomics and haplotype research will probable tailor sub classification. Nevertheless, patho morphological assessment is necessary for class of IBM, categorization of seronegative IIM, and in-intensity characterization of IIM with recognised antibodies. In addition, pathological findings might also additionally offer clues to enhance our knowledge on underlying patho mechanisms and their diagnostic and healing implications. The 2018 ENMCDM, for the primary time, covered a surrogate marker for signature pathway activation (MxA) and DMSA with inside the class criteria. With serological information, 2018 ENMC-DM emphasizes exclusive packing containers of class for non DMSA-antibody-effective IIM with dermatomyositis-like pores and skin lesions. For the subsequent dermatomyositis Muscular disease six hundred www.co-neurology.com Volume 33 Number 5 October 2020 class revision, scattered and diffuse MxA-effective sample have to be covered in dermatomyositis muscle characteristic criteria. In addition, DMSD have to be taken into consideration as spectrum of dermatomyositis because the situation might also additionally have healing implication

Acknowledgement

The author thank the patients whose data were used in this study.

Conflict of Interest

The author declare that there is no conflict of interest.