Utilization patterns and performance of commercial myositis autoantibody panels in routine clinical practice

Amyopathic Dermatomyositis Presenting with Digital Ulcerations: Case Report and Literature Review

ABSTRACT

Clinically amyopathic dermatomyositis (CADM) is a rare subtype of dermatomyositis that presents with cutaneous features and no muscle involvement. This case report describes a 26-year-old woman with recurrent and multiple digital ulcerations coinciding with the start of winter each year. There was no evidence of myopathy, and antibody testing yielded negative results. A diagnosis of CADM was ultimately made based on clinicopathologic correlation. The patient's ulcers demonstrated excellent response to a combination therapy of hydroxychloroquine and potent topical and systemic steroids. Herein, the authors discuss the pathologic and immunologic characteristics of CADM.

Five genes as diagnostic biomarkers of dermatomyositis and their correlation with immune cell infiltration

Background

Dermatomyositis (DM) is a rare autoimmune disease characterized by severe muscle dysfunction, and the immune response of the muscles plays an important role in the development of DM. Currently, the diagnosis of DM relies on symptoms, physical examination, and biopsy techniques. Therefore, we used machine learning algorithm to screen key genes, and constructed and verified a diagnostic model composed of 5 key genes. In terms of immunity, The relationship between 5 genes and immune cell infiltration in muscle samples was analyzed. These diagnostic and immune-cell-related genes may contribute to the diagnosis and treatment of DM.

Methods

GSE5370 and GSE128470 datasets were utilised from the Gene Expression Omnibus database as DM test sets. And we also used R software to merge two datasets and to analyze the results of differentially expressed genes (DEGs) and functional correlation analysis. Then, we could detect diagnostic genes adopting least absolute shrinkage and selection operator (LASSO) logistic regression and support vector machine recursive feature elimination (SVM-RFE) analyses. The validity of putative biomarkers was assessed using the GSE1551 dataset, and we confirmed the area under the receiver operating characteristic curve (AUC) values. Finally, CIBERSORT was used to evaluate immune cell infiltration in DM muscles and the correlations between disease-related biomarkers and immune cells.

Results

In this study, a total of 414 DEGs were screened. ISG15, TNFRSF1A, GUSBP11, SERPINB1 and PTMA were identified as potential DM diagnostic biomarkers(AUC > 0.85),and the expressions of 5 genes in DM group were higher than that in healthy group (p < 0.05). Immune cell infiltration analyses indicated that identified DM diagnostic biomarkers may be associated with M1 macrophages, activated NK cells, Tfh cells, resting NK cells and Treg cells.

Conclusion

The study identified that ISG15, TNFRSF1A, GUSBP11, SERPINB1 and PTMA as potential diagnostic biomarkers of DM and these genes were closely correlated with immune cell infiltration.This will contribute to future studies in diagnosis and treatment of DM.

The associations between myositis autoantibodies and clinical presentations in dermatomyositis

BACKGROUND

The myositis autoantibodies have been widely used clinically in recent years for the identification of an autoantibody-associated clinical phenotype in dermatomyositis (DM) patients. However, correlations between myositis autoantibodies and clinical presentations in different populations are lacking, especially in Taiwan.

OBJECTIVES

To investigate the correlations among cutaneous manifestations, myositis autoantibodies, and systemic diseases, including interstitial lung disease (ILD) and internal malignancy.

METHODS

A retrospective study of patients with histopathologically confirmed cutaneous manifestations of DM was conducted during 2005 to 2020 in Taiwan. A commercial line blot immunoassay technique was used to detect myositis autoantibodies.

RESULTS

A total of 88 DM patients were enrolled, with a mean age of onset of 49.4 years old. The most common systemic features were myositis (56.8%, 50/88), internal malignancy (22.7%, 20/88), dysphagia (19.3%, 17/88), and ILD (17%, 15/88). Among the enrolled patients, 32 patients received serum myositis autoantibodies examination. The most common autoantibodies were ANA (50.7%, 37/73), followed by anti-TIF1-γ (34.4%, 11/32) and anti-MDA5 (31.3%, 10/32) antibodies. Patients with Gottron sign (OR 5.6), arthritis (OR 23.35), or the presence of anti-MDA5 antibody (OR 11.14) were more susceptible to progressing to ILD, whereas patients with pruritus (OR 1.04), dysphagia (OR 6.73), and the presence of ANA (OR 6.29) had significantly higher risks of developing internal malignancies.

CONCLUSIONS

Physicians should pay special attention to certain clinical features, which can help with the early detection of systemic diseases. Cancer screening and myositis autoantibodies examination should be conducted in all DM patients if applicable.

Identification and Prognosis of Patients With Interstitial Pneumonia With Autoimmune Features

BACKGROUND/OBJECTIVE

Patients classified as interstitial pneumonia with autoimmune features (IPAF) have interstitial lung disease (ILD) and features of autoimmunity but do not fulfill criteria for connective tissue diseases (CTDs). Our goal was to identify patients classifiable as IPAF, CTD-ILD, and idiopathic pulmonary fibrosis (IPF) from a preexisting pulmonary cohort and evaluate the prognosis of patients with IPAF.

METHODS

We reviewed the medical records of 456 patients from a single-center pulmonary ILD cohort whose diagnoses were previously established by a multidisciplinary panel that did not include rheumatologists. We reclassified patients as IPAF, CTD-ILD, or IPF. We compared transplant-free survival using Kaplan-Meier methods and identified prognostic factors using Cox models.

RESULTS

We identified 60 patients with IPAF, 113 with CTD-ILD, and 126 with IPF. Transplant-free survival of IPAF was not statistically significantly different from that of CTD-ILD or IPF. Among IPAF patients, male sex (hazard ratio, 4.58 [1.77-11.87]) was independently associated with worse transplant-free survival. During follow-up, only 10% of IPAF patients were diagnosed with CTD-ILD, most commonly antisynthetase syndrome.

CONCLUSION

Despite similar clinical characteristics, most patients with IPAF did not progress to CTD-ILD; those who did often developed antisynthetase syndrome, highlighting the critical importance of comprehensive myositis autoantibody testing in this population. As in other types of ILD, male sex may portend a worse prognosis in IPAF. The routine engagement of rheumatologists in the multidisciplinary evaluation of ILD will help ensure the accurate classification of these patients and help clarify prognostic factors.

The reliability of immunoassays to detect autoantibodies in patients with myositis is dependent on autoantibody specificity

Objectives

In order to address the reliability of commercial assays to identify myositis-specific and -associated autoantibodies, we aimed to compare the results of two commercial immunoassays with the results obtained by protein immunoprecipitation.

Methods

Autoantibody status was determined using radio-labelled protein immunoprecipitation for patients referred to our laboratory for myositis autoantibody characterization. For each autoantibody of interest, the sera from 25 different patients were analysed by line blot (Euroline Myositis Antigen Profile 4, EuroImmun, Lübeck, Germany) and dot blot (D-Tek BlueDiver, Diagnostic Technology, Belrose, NSW, Australia). Sera from 134 adult healthy controls were analysed.

Results

Overall commercial assays performed reasonably well, with high agreement (Cohen’s κ >0.8). Notable exceptions were the detection of rarer anti-synthetases with κ < 0.2 and detection of anti-TIF1γ, where κ was 0.70 for the line blot and 0.31 for dot blot. Further analysis suggested that the proportion of patients with anti-TIF1γ may recognize a conformational epitope, limiting the ability of blotting-based assays that utilize denatured antigen to detect this clinically important autoantibody. A false-positive result occurred in 13.7% of samples analysed by line blot and 12.1% analysed by dot blot.

Conclusion

The assays analysed do not perform well for all myositis-specific and -associated autoantibodies and overall false positives are relatively common. It is crucial that clinicians are aware of the limitations of the methods used by their local laboratory. Results must be interpreted within the clinical context and immunoprecipitation should still be considered in selected cases, such as apparently autoantibody-negative patients where anti-synthetase syndrome is suspected.