Calcinosis in dermatomyositis: Origins and possible therapeutic avenues

Myositis and Its Mimics: Guideline Updates, MRI Characteristics, and New Horizons

Myositis is defined as inflammation within skeletal muscle and is a subcategory of myopathy, which is more broadly defined as any disorder affecting skeletal muscle. Myositis may be encountered as a component of autoimmune and connective tissue disease, where it is described as idiopathic inflammatory myopathy. Myositis can also be caused by infections, as well as toxins and drugs, including newer classes of medications. MRI plays an important role in the diagnosis and evaluation of patients with suspected myositis, but many entities may have imaging features similar to myositis and can be considered myositis mimics. These include muscular dystrophies, denervation, deep venous thrombosis, diabetic myonecrosis, muscle injury, heterotopic ossification, and even neoplasms. In patients with suspected myositis, definitive diagnosis may require integrated analysis of imaging findings with clinical, laboratory, and pathology data. The objectives of this article are to review the fundamental features of myositis, including recent updates in terminology and consensus guidelines for idiopathic inflammatory myopathies, the most important MRI differential diagnostic considerations for myositis (i.e., myositis mimics), and new horizons, including the potential importance of artificial intelligence and multimodal integrated diagnostics in the evaluation of patients with muscle disorders.

Calcinosis in Juvenile Dermatomyositis-Epidemiology, Pathogenesis, Clinical Features, and Treatment: A Systematic Review

PURPOSE OF REVIEW

We performed a systematic review of the literature on the epidemiology, pathogenesis, clinical and laboratory characterization, and treatment of calcinosis in patients with juvenile dermatomyositis (JDM). A qualitative systematic review was conducted from January 1975 to April 2023 according to the PRISMA protocol using three electronic databases: PubMed, Web of Science, and Scopus. Studies were analyzed based on the following eligibility criteria: at least one combination of the terms described in the search strategy appeared in the title, written in English, Portuguese, or Spanish, and addressed the epidemiology, pathogenesis, diagnosis, and treatment of calcinosis in juvenile dermatomyositis. Systematic or scoping reviews, letters, clinical images, book chapters, abstracts, inflammatory myopathy in other connective tissue diseases, idiopathic inflammatory myopathies in adults, and purely qualitative studies were excluded.

RECENT FINDINGS

Seventy-five studies were included. According to the literature, calcinosis is common in women, around five years old, with three years of disease in association with osteoarticular, cutaneous, pulmonary manifestations, and fever. The pathogenesis is still unknown, but the participation of interleukin 1 and 6, tumor necrosis factor alpha, and innate immunity dysregulation seem to be involved. Common autoantibodies are anti-NXP-2, anti-MDA-5, and anti-Mi-2, and their treatment remains controversial. Prospective, randomized, controlled studies are needed to evaluate treatment protocols and map the natural history of this serious complication. Calcinosis seems to be more common in White female children with muscle weakness, fever, arthritis, severe pulmonary, and skin involvement with anti-NXP-2, anti-MDA-5, and anti-Mi-2 autoantibodies. The multitargets and aggressive treatment is recommended.

Autoimmune inflammatory myopathy biomarkers

The autoimmune inflammatory myopathy disease spectrum, commonly known as myositis, is a group of systemic diseases that mainly affect the muscles, skin and lungs. Biomarker assessment helps in understanding disease mechanisms, allowing for the implementation of precise strategies in the classification, diagnosis, and management of these diseases. This review examines the pathogenic mechanisms and highlights current data on blood and tissue biomarkers of autoimmune inflammatory myopathies.

Clinical profile of anti-NXP-2 antibody-positive inflammatory myositis and outcome in an Indian population

INTRODUCTION

Myositis-specific antibodies (MSA) play an important role in the clinical presentation and prognosis of patients with idiopathic inflammatory myositis (IIM). Anti-NXP-2 is one of the newly described MSA.

OBJECTIVE

We aimed to describe various clinical presentations associated with anti-NXP2 antibodies and assess response to treatment.

METHODS

In this retrospective study, the electronic medical records of all patients who tested positive for anti-NXP2 during June 2019 to April 2022 were screened. Details of demography, clinical presentation, and treatment data were recorded. The anti-NXP2 was tested using the Euro line test kit. Any patient who had an intensity of ≥1+ was considered testing positive. The diagnosis of IIM was reviewed after applying the 2017 European League of Rheumatology (EULAR)/American College of Rheumatology (ACR) criteria of myositis.

RESULTS

Among the 660 suspected patients, 470 (71.2%) patients were positive for IIM, and 28 (5.95%) patients were positive for anti-NXP2. From anti-NXP2-antibody positive, 21/470 (4.46%) patients fulfilled criteria for IIM. Among 12 adult (57.14%) patients with IIM, 7 (58.33%) presented as polymyositis (PM) and 5 (41.6%) as dermatomyositis (DM) with median age at presentation of 45 (IQR: 25-58) years. Calcinosis and subcutaneous oedema were observed in 4 (19%) and 2 (9.52%), respectively; myalgia in 6 (28.6%); and distal muscle weakness in 5 (23.8%) patients. Malignancy at the time of diagnosis was observed in two adults with IIM (16.7%), one with DM (intraductal breast cancer), and another with PM (anaplastic large cell lymphoma). Remaining, 9 had juvenile dermatomyositis (JDM) with a median age of 4 (IQR: 3-8) years. Seven (77.8%) patients with JDM had skin rash specific for DM (heliotrope rash and Gottron's papule). None of the patients had cardiac and lung involvement, while GI symptoms, especially dysphagia, were present in 5 (23.8%) patients. During a median follow-up of 19 months (IQR: 12-26 months), 19/19 patients reported improvement and were in remission with treatment.

CONCLUSION

The current study shows that adult DM patients with anti-NXP-2 autoantibodies have a unique clinical phenotype. Its presentation differs between adult and JDM, even in different parts of the world. Muscle weakness is mild and responds to treatment. Dysphagia needs more time and aggressive IS for improvement as compared to other muscle involvement. Key Points • Anti-NXP-2 antibody presentation varied from adult to child, as in different parts of the world. • In Indian adult patients, non-specific skin manifestations were more common, whereas in JDM, specific skin features were common. • There was less likely involvement of the lung and heart. But more risk of GI involvement requiring aggressive management. • Adult with anti-NXP-2 antibody should be screened for malignancy at the time of presentation.

Role of mitochondria in the myopathy of juvenile dermatomyositis and implications for skeletal muscle calcinosis

OBJECTIVES

To elucidate mechanisms contributing to skeletal muscle calcinosis in patients with juvenile dermatomyositis.

METHODS

A well-characterized cohorts of JDM (n = 68), disease controls (polymyositis, n = 7; juvenile SLE, n = 10, and RNP + overlap syndrome, n = 12), and age-matched health controls (n = 17) were analyzed for circulating levels of mitochondrial (mt) markers including mtDNA, mt-nd6, and anti-mitochondrial antibodies (AMAs) using standard qPCR, ELISA, and novel-in-house assays, respectively. Mitochondrial calcification of affected tissue biopsies was confirmed using electron microscopy and energy dispersive X-ray analysis. A human skeletal muscle cell line, RH30, was used to generate an in vitro calcification model. Intracellular calcification is measured by flow cytometry and microscopy. Mitochondria were assessed for mtROS production and membrane potential by flow cytometry and real-time oxygen consumption rate by Seahorse bioanalyzer. Inflammation (interferon-stimulated genes) was measured by qPCR.

RESULTS

In the current study, patients with JDM exhibited elevated levels of mitochondrial markers associated with muscle damage and calcinosis. Of particular interest are AMAs predictive of calcinosis. Human skeletal muscle cells undergo time- and dose-dependent accumulation of calcium phosphate salts with preferential localization to mitochondria. Calcification renders skeletal muscle cells mitochondria stressed, dysfunctional, destabilized, and interferogenic. Further, we report that inflammation induced by interferon-alpha amplifies mitochondrial calcification of human skeletal muscle cells via the generation of mitochondrial reactive oxygen species (mtROS).

CONCLUSIONS

Overall, our study demonstrates the mitochondrial involvement in the skeletal muscle pathology and calcinosis of JDM and mtROS as a central player in the calcification of human skeletal muscle cells. Therapeutic targeting of mtROS and/or upstream inducers, such as inflammation, may alleviate mitochondrial dysfunction, leading to calcinosis. AMAs can potentially identify patients with JDM at risk for developing calcinosis.

The role of bDMARDs in idiopathic inflammatory myopathies: A systematic literature review

Idiopathic inflammatory myopathies (IIM) are a group of different conditions typically affecting striate muscle, lung, joints, skin and gastrointestinal tract. Treatment typically relies on glucocorticoids and synthetic immunosuppressants, but the occurrence of refractory, difficult to treat, manifestations, may require more aggressive treatment, borrowed from other autoimmune diseases, including biologic disease modifying drugs (bDMARDs). In this regard, we conducted a systemic literature review in order to depict the current evidence about the use of bDMARDs in IIM. A total of 78 papers, published during the last 21 years, were retrieved. The majority of patients was treated with TNF-α inhibitors, whose effectiveness was assessed particularly in recalcitrant striate muscle, skin and joints involvement. Rituximab, whose evidence is supported by a large number of real-life studies and trials, seems to be an excellent option in case of ILD and anti-synthetase syndrome, while Tocilizumab, despite not meeting primary and secondary endpoints in a recently published clinical trial, proved its effectiveness in rapidly progressing ILD. Similarly, Abatacept, studied in a phase IIb clinical trial with conflicting evidence, was reported to be effective in some case reports of refractory dermatomyositis. Less data exist for anti-IL1 and anti-IL23 agents, which were employed particularly for inclusion body myositis and severe skin disease, respectively. This study provides an organ-focused assessment of bDMARDs in IIM, which display encouraging results in the treatment of refractory subsets of disease.

Calcinosis in juvenile dermatomyositis: Updates on pathogenesis and treatment

Calcinosis, or the deposition of insoluble calcium salts in the skin, subcutaneous tissue, fascia, tendons, and muscles, is a feared complication of juvenile dermatomyositis. Calcinosis is estimated to affect up to 40% of patients with juvenile dermatomyositis and contributes to significant disease morbidity. Calcinosis can be challenging to treat, and the most effective treatment remains unknown because of a lack of comparative studies. We aim to review the literature published in the last 5 years to summarize updates on the pathogenesis and treatment of calcinosis in juvenile dermatomyositis and describe future areas for research.