Autoantibodies to survival of motor neuron complex in patients with polymyositis: immunoprecipitation of D, E, F, and G proteins without other components of small nuclear ribonucleoproteins

Evolution of diagnostic criteria and new insights into clinical testing in mixed connective tissue disease; anti-survival motor neuron complex antibody as a novel marker of severity of the disease

Mixed connective tissue disease (MCTD) is an autoimmune disorder characterized by a combination of clinical features from systemic lupus erythematosus, systemic sclerosis, and inflammatory muscle disease, along with the presence of positive anti-U1-ribonucleoprotein (U1-RNP) antibodies. The exact etiology of the disease remains unclear, but it is believed to involve vascular damage within the context of heightened autoimmune responses. Consequently, Raynaud's phenomenon and pulmonary arterial hypertension are observed in patients with MCTD. While specific biomarkers for MCTD have not yet been identified, the recent study of the utility of anti-survival motor neuron complex (SMN) antibodies in MCTD suggests a promising avenue for further research and the accumulation of additional evidence.

Anti-survival motor neuron complex antibodies as a novel biomarker for pulmonary arterial hypertension and interstitial lung disease in mixed connective tissue disease

OBJECTIVE

The presence of anti-U1 RNP antibodies (Abs) is critical for diagnosing MCTD. The aim of this study is to evaluate the clinical relevance of anti-survival motor neuron (SMN) complex Abs, which often coexist with anti-U1 RNP Abs.

METHODS

A total of 158 newly diagnosed consecutive cases of SLE, SSc or MCTD with anti-U1 RNP Abs were enrolled in this multicentre observational study between April 2014 and August 2022. Serum anti-SMN complex Abs were screened by immunoprecipitation of 35S-methionine-labelled cell extracts, and associations between anti-SMN complex Abs positivity and clinical characteristics were analysed.

RESULTS

Anti-SMN complex Abs were detected in 36% of MCTD patients, which was significantly higher than that in SLE (8%) or SSc (12%). Among MCTD patients classified based on the combination of the clinical features of SLE, SSc and idiopathic inflammatory myopathies, anti-SMN complex Abs showed the highest prevalence in a subset with clinical features of all three components. Anti-SMN complex Abs-positive MCTD had a higher prevalence of pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD), which are related to poor prognosis, than negative patients. Moreover, all three cases of death within 1 year of the treatment were positive for anti-SMN complex Abs.

CONCLUSIONS

Anti-SMN complex Abs is the first biomarker of a typical subset of MCTD which bears organ damages such as PAH and ILD.

Analytic and Clinical Validity of Myositis-Specific Antibodies by Line-Blot Immunoassay Is Essential

OBJECTIVES

This study assessed the concordance between line blot (LB) and immunoprecipitation (IP) assays for detecting myositis-specific antibodies (MSAs) in idiopathic inflammatory myopathies (IIMs) and their association with IIM subtypes.

METHODS

One hundred patients with IIM were enrolled, and MSA was detected using LB and IP. The IIM subtypes, including immune-mediated necrotizing myopathy-like, anti-tRNA synthetase syndrome-like, and clinically amyopathic dermatomyositis-like, were clinically diagnosed. The validity and reliability of the LB compared with the IP were evaluated. Optimal cutoff levels for LB were determined using various statistical methods including Cohen κ, Gwet's AC, diagnostic odds ratios, and receiver operating characteristic analysis.

RESULTS

Line blot exhibited lower specificity and accuracy than IP in predicting IIM subtypes. Some MSAs performed better at higher LB cutoff values. Anti-signal recognition particle antibodies showed poor performance in predicting the immune-mediated necrotizing myopathy-like subtype using LB. Raising the cutoffs improved the reliability of anti-threonyl-tRNA synthetase and anti-signal recognition particle antibodies. Anti-histidyl-tRNA synthetase antibodies performed well at lower positivity, whereas diagnostic odds ratios increased for anti-transcription intermediary factor 1γ and anti-nuclear matrix protein 2 with higher cutoffs.

CONCLUSIONS

Inconsistencies between LB and IP have been observed in patients with IIM. Individual optimal cutoffs for MSA by LB correlating with IP were determined. Rheumatologists should consider the differences between LB and IP results when classifying IIM subtypes.

Systemic sclerosis associated myopathy: how to treat

Purpose of review

Systemic sclerosis (SSc) and myositis are two different entities that may coexist as an overlap syndrome. Immunological biomarkers such as anti-PM/Scl or anti-Ku reinforce the syndrome. This review is focused on the treatment of different and characteristic manifestations of this syndrome.

Recent findings

Among the different phenotypes of muscle involvement in patients with SSc, the fibrotic pattern and the sporadic inclusion body myositis must be identified early to avoid a futile immunosuppressive treatment. Other forms such as dermatomyositis, non-specific myositis and immune-mediated necrotizing myopathy need to receive conventional immunosuppressive therapy considering that high dose of glucocorticoids may induce a scleroderma renal crisis in patients with SSc. Physicians must be aware of the existence of a "double trouble" association of hereditary myopathy with an autoimmune phenomenon. Several autoantibodies, mainly anti-PM/Scl and anti-Ku may help to define specific phenotypes with characteristic clinical manifestations that need a more specific therapy. Vasculopathy is one of the underlying mechanisms that link SSc and myositis. Recent advances in this topic are reviewed.

Summary

Current treatment of SSc associated myopathy must be tailored to specific organs involved. Identifying the specific clinical, pathological, and immunological phenotypes may help to take the correct therapeutic decisions.

Anti-SMN autoantibodies in mixed connective tissue disease are associated with a severe systemic sclerosis phenotype

OBJECTIVES

The survival of motor neuron (SMN) complex has an essential role in the assembly of small nuclear ribonucleoproteins (RNP). Recent reports have described autoantibodies (aAbs) to the SMN complex as novel biomarkers in anti-U1RNP+ myositis patients. The aim of this study was to compare phenotypic features of anti-U1RNP+ mixed connective tissue disease (MCTD) patients with and without anti-SMN aAbs.

METHODS

A retrospective MCTD cohort was studied. Addressable laser bead immunoassay was used to detect specific anti-SMN aAbs with <300 mean fluorescence intensity (MFI) as normal reference range, 300-999 MFI as low-titre and ≥1000 MFI as high-titre positivity. Comparison of clinical features between anti-SMN+ and anti-SMN- subgroups used two-tailed Fisher's exact test, and logistic regression analyses.

RESULTS

Sixty-six patients were included. Median age at MCTD diagnosis was 40.6 years, and duration of follow-up was 12 years. Based on the highest available titre, 39 (59%) were anti-SMN+: 10 (26%) had low titre and 29 (74%) had high titre. Anti-SMN+ patients had a higher frequency of fingertip pitting scars (anti-SMN+ 23% vs anti-SMN- 4%, p=0.04), lower gastrointestinal (GI) involvement (26% vs 4%, p=0.04), and myocarditis (16% vs 0%, p=0.04). The combined outcome of pitting scars and/or lower GI involvement and/or myositis and/or myocarditis was highest among high-titre anti-SMN+ patients: adjusted OR 7.79 (2.33 to 30.45, p=0.002).

CONCLUSIONS

Anti-SMN aAbs were present in 59% of our MCTD cohort. Their presence, especially at high-titres, was associated with a severe systemic sclerosis (scleroderma) phenotype including myositis, myocarditis and lower GI involvement.

The axis of complement C1 and nucleolus in antinuclear autoimmunity

Antinuclear autoantibodies (ANA) are heterogeneous self-reactive antibodies that target the chromatin network, the speckled, the nucleoli, and other nuclear regions. The immunological aberration for ANA production remains partially understood, but ANA are known to be pathogenic, especially, in systemic lupus erythematosus (SLE). Most SLE patients exhibit a highly polygenic disease involving multiple organs, but in rare complement C1q, C1r, or C1s deficiencies, the disease can become largely monogenic. Increasing evidence point to intrinsic autoimmunogenicity of the nuclei. Necrotic cells release fragmented chromatins as nucleosomes and the alarmin HMGB1 is associated with the nucleosomes to activate TLRs and confer anti-chromatin autoimmunogenecity. In speckled regions, the major ANA targets Sm/RNP and SSA/Ro contain snRNAs that confer autoimmunogenecity to Sm/RNP and SSA/Ro antigens. Recently, three GAR/RGG-containing alarmins have been identified in the nucleolus that helps explain its high autoimmunogenicity. Interestingly, C1q binds to the nucleoli exposed by necrotic cells to cause protease C1r and C1s activation. C1s cleaves HMGB1 to inactive its alarmin activity. C1 proteases also degrade many nucleolar autoantigens including nucleolin, a major GAR/RGG-containing autoantigen and alarmin. It appears that the different nuclear regions are intrinsically autoimmunogenic by containing autoantigens and alarmins. However, the extracellular complement C1 complex function to dampen nuclear autoimmunogenecity by degrading these nuclear proteins.

Scleromyositis: A distinct novel entity within the systemic sclerosis and autoimmune myositis spectrum. Implications for care and pathogenesis

Systemic sclerosis and autoimmune myositis are both associated with decreased quality of life and increased mortality. Their prognosis and management largely depend on the disease subgroups. Indeed, systemic sclerosis is a heterogeneous disease, the two predominant forms of the disease being limited and diffuse scleroderma. Autoimmune myositis is also a heterogeneous group of myopathies that classically encompass necrotizing myopathy, antisynthetase syndrome, dermatomyositis and inclusion body myositis. Recent data revealed that an additional disease subset, denominated "scleromyositis", should be recognized within both the systemic sclerosis and the autoimmune myositis spectrum. We performed an in-depth review of the literature with the aim of better delineating scleromyositis. Our review highlights that this concept is supported by recent clinical, serological and histopathological findings that have important implications for patient management and understanding of the disease pathophysiology. As compared with other subsets of systemic sclerosis and autoimmune myositis, scleromyositis patients can present with a characteristic pattern of muscle involvement (i.e. distribution of muscle weakness) along with multisystemic involvement, and some of these extra-muscular complications are associated with poor prognosis. Several autoantibodies have been specifically associated with scleromyositis, but they are not currently integrated in diagnostic and classification criteria for systemic sclerosis and autoimmune myositis. Finally, striking vasculopathic lesions at muscle biopsy have been shown to be hallmarks of scleromyositis, providing a strong anatomopathological substratum for the concept of scleromyositis. These findings bring new insights into the pathogenesis of scleromyositis and help to diagnose this condition, in patients with subtle SSc features and/or no autoantibodies (i.e. "seronegative" scleromyositis). No guidelines are available for the management of these patients, but recent data are showing the way towards a new therapeutic approach dedicated to these patients.

VI Brazilian consensus guidelines for detection of anti-cell autoantibodies on HEp-2 cells

BACKGROUND

The VI Brazilian Consensus on Autoantibodies against HEp-2 cells for determination of autoantibodies against cellular constituents on HEp-2 cells was held on September, 2019, in Fortaleza (CE, Brazil). The guidelines in this edition were formulated by the group of Brazilian experts discussing the classification of complex patterns, the classification of the nuclear discrete dots (few and multiple), the identification of the discrete fine speckled pattern (AC-4a) and improvements on the ANA report.

MAINBODY

Sixteen Brazilian researchers and experts from universities and clinical laboratories representing the various geographical regions of Brazil participated in the meeting. Four main topics were discussed: (1) How to classify patterns with fluorescence in more than one cell compartment considering three relevant categoris: composite patterns, mixed patterns and multiple patterns; (2) The splitting of the discrete nuclear dots pattern into the multiple discrete nuclear dots (AC-6) and few discrete nuclear dots (AC-7) patterns, respectively; (3) Inclusion of a novel nuclear pattern characterized by discrete fine speckled pattern highly associated with antibodies to SS-A/Ro60, classified as AC-4a. In addition, adjustments on the Brazilian Consensus nomenclature were implemented aiming to harmonize the designation of some patterns with the International Consensus on ANA Patterns (ICAP). Furthermore, the designations of the PCNA-like pattern (AC-13), CENP-F-like pattern (AC-14) and Topo I-like pattern (AC-29) were adjusted in accordance to ICAP. Finally, there was a recommendation for adjustment in the test report in order to address the status of nuclear envelope staining. For all topics, the aim was to establish specific guidelines for laboratories and clinicians. All recommendations were based on consensus among participants. All recommendations from the V Consensus were maintained and there was relevant progress in the BCA/HEp-2 guidelines and further harmonization with ICAP.

CONCLUSION

The VI BCA/HEp-2 edition was successful in establishing important recommendations regarding the classification of complex patterns, in supporting the identification of a novel pattern within the AC-4 group and in the harmonization process with the ICAP terminology.

An Autoantigen Atlas From Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. We used DS-affinity proteomics to define the autoantigen-ome of lung fibroblasts and bioinformatics analyses to study the relationship between autoantigenic proteins and COVID-induced alterations. Using DS-affinity, we identified an autoantigen-ome of 408 proteins from human HFL1 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigen-ome have thus far been found to be altered at protein or RNA levels in SARS-CoV-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a connection between COVID infection and autoimmunity. The vast number of COVID-altered proteins with high intrinsic propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles suggests a need for long-term monitoring of autoimmunity in COVID. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic, such as “long COVID” syndrome.

Myositis with prominent B-cell aggregates causing shrinking lung syndrome in systemic lupus erythematosus: a case report

Background

Shrinking lung syndrome (SLS) is a rare manifestation of systemic lupus erythematosus (SLE) characterized by decreased lung volumes and diaphragmatic weakness in a dyspneic patient. Chest wall dysfunction secondary to pleuritis is the most commonly proposed cause. In this case report, we highlight a new potential mechanism of SLS in SLE, namely diaphragmatic weakness associated with myositis with CD20 positive B-cell aggregates.

Case presentation

A 51-year-old Caucasian woman was diagnosed with SLE and secondary Sjögren’s syndrome based on a history of pleuritis, constrictive pericarditis, polyarthritis, photosensitivity, alopecia, oral ulcers, xerophthalmia and xerostomia. Serologies were significant for positive antinuclear antibodies, anti-SSA, lupus anticoagulant and anti-cardiolopin. Blood work revealed a low C3 and C4, lymphopenia and thrombocytopenia. She was treated with with low-dose prednisone and remained in remission with oral hydroxychloroquine. Seven years later, she developed mild proximal muscle weakness and exertional dyspnea. Pulmonary function testing revealed a restrictive pattern with small lung volumes. Pulmonary imaging showed elevation of the right hemidiaphragm without evidence of interstitial lung disease. Diaphragmatic ultrasound was suggestive of profound diaphragmatic weakness and dysfunction. Based on these findings, a diagnosis of SLS was made. Her proximal muscle weakness was investigated, and creatine kinase (CK) levels were normal. Electromyography revealed fibrillation potentials in the biceps, iliopsoas, cervical and thoracic paraspinal muscles, and complex repetitive discharges in cervical paraspinal muscles. Biceps muscle biopsy revealed dense endomysial lymphocytic aggregates rich in CD20 positive B cells, perimysial fragmentation with plasma cell-rich perivascular infiltrates, diffuse sarcolemmal upregulation of class I MHC, perifascicular upregulation of class II MHC, and focal sarcolemmal deposition of C5b-9. Treatment with prednisone 15 mg/day and oral mycophenolate mofetil 2 g/day was initiated. Shortness of breath and proximal muscle weakness improved significantly.

Conclusion

Diaphragmatic weakness was the inaugural manifestation of myositis in this patient with SLE. The spectrum of myologic manifestations of myositis with prominent CD20 positive B-cell aggregates in SLE now includes normal CK levels and diaphragmatic involvement, in association with SLS.

Polymyositis: does it really exist as a distinct clinical subset?

PURPOSE OF REVIEW

To summarize information on polymyositis; diagnosis, definitions, published data and opinions.

RECENT FINDINGS

Polymyositis originally referred to inflammatory muscle diseases presenting with muscle weakness and inflammatory cell infiltrates on muscle tissue visible by microscopy. Over time and with improved technology to immunophenotype infiltrating inflammatory cells and characterize muscle fibres, the meaning of polymyositis changed and became more specific. There is ongoing controversy over the term polymyositis, with proponents for a strict definition based on histopathological and immunohistochemical features on muscle biopsies whereas others advocate for a broader clinical and histopathological phenotype. Over the past decades, the discovery of several myositis-specific autoantibodies together with distinct histopathological features have enabled the identification of new subsets previously labelled as polymyositis notably the antisynthetase syndrome and the immune-mediated necrotizing myopathies thus reducing the number of patients classified as polymyositis.

SUMMARY

There are still a small number of patients among the idiopathic inflammatory myopathies that can be classified as polymyositis as discussed in this review but the entity is now considered relatively rare.

Phylogenetic Comparison and Splicing Analysis of the U1 snRNP-specific Protein U1C in Eukaryotes

As a pivotal regulator of 5’ splice site recognition, U1 small nuclear ribonucleoprotein (U1 snRNP)-specific protein C (U1C) regulates pre-mRNA splicing by interacting with other components of the U1 snRNP complex. Previous studies have shown that U1 snRNP and its components are linked to a variety of diseases, including cancer. However, the phylogenetic relationships and expression profiles of U1C have not been studied systematically. To this end, we identified a total of 110 animal U1C genes and compared them to homologues from yeast and plants. Bioinformatics analysis shows that the structure and function of U1C proteins is relatively conserved and is found in multiple copies in a few members of the U1C gene family. Furthermore, the expression patterns reveal that U1Cs have potential roles in cancer progression and human development. In summary, our study presents a comprehensive overview of the animal U1C gene family, which can provide fundamental data and potential cues for further research in deciphering the molecular function of this splicing regulator.

A Master Autoantigen-ome Links Alternative Splicing, Female Predilection, and COVID-19 to Autoimmune Diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare but reported adverse effects of the currently available COVID vaccines.

Recognising the spectrum of scleromyositis: HEp-2 ANA patterns allow identification of a novel clinical subset with anti-SMN autoantibodies

Objective

To describe systemic sclerosis (SSc) with myopathy in patients without classic SSc-specific and SSc-overlap autoantibodies (aAbs), referred to as seronegative scleromyositis.

Methods

Twenty patients with seronegative scleromyositis diagnosed by expert opinion were analysed retrospectively for SSc features at myositis diagnosis and follow-up, and stratified based on HEp-2 nuclear patterns by indirect immunofluorescence (IIF) according to International Consensus of Autoantibody Patterns. Specificities were analysed by protein A−assisted immunoprecipitation. Myopathy was considered an organ involvement of SSc.

Results

SSc sine scleroderma was a frequent presentation (45%) at myositis diagnosis. Myositis was the most common first non-Raynaud manifestation of SSc (55%). Lower oesophagal dysmotility was present in 10 of 11 (91%) investigated patients. At follow-up, 80% of the patients met the American College of Rheumatology/EULAR SSc classification criteria. Two-thirds of patients had a positive HEp-2 IIF nuclear pattern (all with titers ≥1/320), defining three novel scleromyositis subsets. First, antinuclear antibody (ANA)-negative scleromyositis was associated with interstitial lung disease (ILD) and renal crisis. Second, a speckled pattern uncovered multiple rare SSc-specific aAbs. Third, the nuclear dots pattern was associated with aAbs to survival of motor neuron (SMN) complex and a novel scleromyositis subset characteriszed by calcinosis but infrequent ILD and renal crisis.

Conclusions

SSc skin involvement is often absent in early seronegative scleromyositis. ANA positivity, Raynaud phenomenon, SSc-type capillaroscopy and/or lower oesophagal dysmotility may be clues for scleromyositis. Using HEp-2 IIF patterns, three novel clinicoserological subsets of scleromyositis emerged, notably (1) ANA-negative, (2) ANA-positive with a speckled pattern and (3) ANA-positive with nuclear dots and anti-SMN aAbs.

Phylogenetic comparison and splice site conservation of eukaryotic U1 snRNP-specific U1-70K gene family

Eukaryotic cells can expand their coding ability by using their splicing machinery, spliceosome, to process precursor mRNA (pre-mRNA) into mature messenger RNA. The mega-macromolecular spliceosome contains multiple subcomplexes, referred to as small nuclear ribonucleoproteins (snRNPs). Among these, U1 snRNP and its central component, U1-70K, are crucial for splice site recognition during early spliceosome assembly. The human U1-70K has been linked to several types of human autoimmune and neurodegenerative diseases. However, its phylogenetic relationship has been seldom reported. To this end, we carried out a systemic analysis of 95 animal U1-70K genes and compare these proteins to their yeast and plant counterparts. Analysis of their gene and protein structures, expression patterns and splicing conservation suggest that animal U1-70Ks are conserved in their molecular function, and may play essential role in cancers and juvenile development. In particular, animal U1-70Ks display unique characteristics of single copy number and a splicing isoform with truncated C-terminal, suggesting the specific role of these U1-70Ks in animal kingdom. In summary, our results provide phylogenetic overview of U1-70K gene family in vertebrates. In silico analyses conducted in this work will act as a reference for future functional studies of this crucial U1 splicing factor in animal kingdom.

Autoantibody Discovery, Assay Development and Adoption: Death Valley, the Sea of Survival and Beyond

Dating to the discovery of the Lupus Erythematosus (LE) cell in 1948, there has been a dramatic growth in the discovery of unique autoantibodies and their cognate targets, all of which has led to the availability and use of autoantibody testing for a broad spectrum of autoimmune diseases. Most studies of the sensitivity, specificity, commutability, and harmonization of autoantibody testing have focused on widely available, commercially developed and agency-certified autoantibody kits. However, this is only a small part of the spectrum of autoantibody tests that are provided through laboratories world-wide. This manuscript will review the wider spectrum of testing by exploring the innovation pathway that begins with autoantibody discovery followed by assessment of clinical relevance, accuracy, validation, and then consideration of regulatory requirements as an approved diagnostic test. Some tests are offered as "Research Use Only (RUO)", some as "Laboratory Developed Tests (LDT)", some enter Health Technology Assessment (HTA) pathways, while others are relegated to a "death valley" of autoantibody discovery and become "orphan" autoantibodies. Those that achieve regulatory approval are further threatened by the business world's "Darwinian Sea of Survival". As one example of the trappings of autoantibody progression or failure, it is reported that more than 200 different autoantibodies have been described in systemic lupus erythematosus (SLE), a small handful (~10%) of these have achieved regulatory approval and are widely available as commercial diagnostic kits, while a few others may be available as RUO or LDT assays. However, the vast majority (90%) are orphaned and languish in an autoantibody 'death valley'. This review proposes that it is important to keep an inventory of these "orphan autoantibodies" in 'death valley' because, with the increasing availability of multi-analyte arrays and artificial intelligence (MAAI), some can be rescued to achieve a useful role in clinical diagnostic especially in light of patient stratification and precision medicine.

Histopathological features of systemic sclerosis-associated myopathy: A scoping review

BACKGROUND

Scleromyositis (SM) is an emerging subset of myositis associated with features of systemic sclerosis (SSc) but it is currently not recognized as a distinct histopathological subset by the European NeuroMuscular Center (ENMC). Our aim was to review studies reporting muscle biopsies from SSc patients with myositis and to identify unique histopathological features of SM.

METHODS

A scoping review was conducted and included all studies reporting histopathological findings in SSc patients with myositis searching the following databases: PubMed, MEDLINE, EMBASE, CINAHL and EBM-Reviews. Clinical, serological, and histopathological data were extracted using a standardized protocol.

RESULTS

Out of 371 citations, 77 studies that included 559 muscle biopsies were extracted. Fifty-seven percent (n = 227/400) had inflammatory infiltrates, predominantly T cells, which were endomysial (49%), perimysial (42%) and perivascular (41%). Few studies (18%, n = 8/44) evaluated the presence of B-cells. Myofiber atrophy was present in 48% (n = 104/218) of biopsies, and was predominantly perifascicular in 19% (n = 6/31), with necrosis reported in 56% (n = 162/290) of cases. Sarcolemmal MHC-I upregulation was found in 72% (n = 64/89) of biopsies. Non-specified C5b-9 deposition was described in 39% of muscle biopsies (n = 28/72). Neurogenic features were present in 23% (n = 44/191); endomysial fibrosis was reported in 35% (n = 120/340); and rimmed vacuoles were observed in 32% (n = 11/34) of biopsies. Capillaropathy, such as capillary dropout and/or ultrastructural endothelial abnormalities, was reported in 33% (n = 43/129) of cases. Reported ENMC categories were mainly polymyositis (21%), non-specific myositis (19%), immune-mediated necrotizing myopathy (16%), and dermatomyositis (8%). Histopathological features were analyzed according to serological subtypes in 28 studies, including anti-PM-Scl (n = 48), -Ku (n = 23) and -U1RNP (n = 90). Most of these biopsies demonstrated inflammatory infiltrates (range 49-85%) as well as MHC-I expression (range 63-81%). Necrosis was associated with anti-Ku (85%) and anti-U1RNP (73%), while anti-Ku was also associated with neurogenic features and rimmed vacuoles in 57% and 25% of cases, respectively.

CONCLUSION

Our review suggests that SM is characterized by heterogeneous pathological features using definitions included in current histopathological criteria. Whether a distinct histopathological signature exists in SM remains to be determined. SSc-specific and SSc-associated autoantibodies may help define more homogeneous histopathological subsets.

An autoantigen profile of human A549 lung cells reveals viral and host etiologic molecular attributes of autoimmunity in COVID-19

We aim to establish a comprehensive COVID-19 autoantigen atlas in order to understand autoimmune diseases caused by SARS-CoV-2 infection. Based on the unique affinity between dermatan sulfate and autoantigens, we identified 348 proteins from human lung A549 cells, of which 198 are known targets of autoantibodies. Comparison with current COVID data identified 291 proteins that are altered at protein or transcript level in SARS-CoV-2 infection, with 191 being known autoantigens. These known and putative autoantigens are significantly associated with viral replication and trafficking processes, including gene expression, ribonucleoprotein biogenesis, mRNA metabolism, translation, vesicle and vesicle-mediated transport, and apoptosis. They are also associated with cytoskeleton, platelet degranulation, IL-12 signaling, and smooth muscle contraction. Host proteins that interact with and that are perturbed by viral proteins are a major source of autoantigens. Orf3 induces the largest number of protein alterations, Orf9 affects the mitochondrial ribosome, and they and E, M, N, and Nsp proteins affect protein localization to membrane, immune responses, and apoptosis. Phosphorylation and ubiquitination alterations by viral infection define major molecular changes in autoantigen origination. This study provides a large list of autoantigens as well as new targets for future investigation, e.g., UBA1, UCHL1, USP7, CDK11A, PRKDC, PLD3, PSAT1, RAB1A, SLC2A1, platelet activating factor acetylhydrolase, and mitochondrial ribosomal proteins. This study illustrates how viral infection can modify host cellular proteins extensively, yield diverse autoantigens, and trigger a myriad of autoimmune sequelae. Our work provides a rich resource for studies into “long COVID” and related autoimmune sequelae.

An Autoantigen-ome from HS-Sultan B-Lymphoblasts Offers a Molecular Map for Investigating Autoimmune Sequelae of COVID-19

To understand how COVID-19 may induce autoimmune diseases, we have been compiling an atlas of COVID-autoantigens (autoAgs). Using dermatan sulfate (DS) affinity enrichment of autoantigenic proteins extracted from HS-Sultan lymphoblasts, we identified 362 DS-affinity proteins, of which at least 201 (56%) are confirmed autoAgs. Comparison with available multi-omic COVID data shows that 315 (87%) of the 362 proteins are affected in SARS-CoV-2 infection via altered expression, interaction with viral components, or modification by phosphorylation or ubiquitination, at least 186 (59%) of which are known autoAgs. These proteins are associated with gene expression, mRNA processing, mRNA splicing, translation, protein folding, vesicles, and chromosome organization. Numerous nuclear autoAgs were identified, including both classical ANAs and ENAs of systemic autoimmune diseases and unique autoAgs involved in the DNA replication fork, mitotic cell cycle, or telomerase maintenance. We also identified many uncommon autoAgs involved in nucleic acid and peptide biosynthesis and nucleocytoplasmic transport, such as aminoacyl-tRNA synthetases. In addition, this study found autoAgs that potentially interact with multiple SARS-CoV-2 Nsp and Orf components, including CCT/TriC chaperonin, insulin degrading enzyme, platelet-activating factor acetylhydrolase, and the ezrin-moesin-radixin family. Furthermore, B-cell-specific IgM-associated ER complex (including MBZ1, BiP, heat shock proteins, and protein disulfide-isomerases) is enriched by DS-affinity and up-regulated in B-cells of COVID-19 patients, and a similar IgH-associated ER complex was also identified in autoreactive pre-B1 cells in our previous study, which suggests a role of autoreactive B1 cells in COVID-19 that merits further investigation. In summary, this study demonstrates that virally infected cells are characterized by alterations of proteins with propensity to become autoAgs, thereby providing a possible explanation for infection-induced autoimmunity. The COVID autoantigen-ome provides a valuable molecular resource and map for investigation of COVID-related autoimmune sequelae and considerations for vaccine design.

An Autoantigen Atlas from Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. Using DS affinity, we identified an autoantigenome of 408 proteins from human fetal lung fibroblast HFL11 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigenome have thus far been found to be altered at protein or RNA levels in SARS-Cov-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a strong connection between viral infection and autoimmunity. The vast number of COVID-altered proteins with propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles raises concerns about potential adverse effects of mRNA vaccines. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic.

V Brazilian consensus guidelines for detection of anti-cell autoantibodies on hep-2 cells

BACKGROUND

The V Brazilian Consensus for determination of autoantibodies against cellular constituents on HEp-2 cells, held in Brasilia (DF, Brazil) on August 27, 2016, discussed the harmonization between the Brazilian Consensus on ANA (BCA) guidelines and the International Consensus on ANA Patterns (ICAP) recommendations ( www.anapatterns.org ). Initial guidelines were formulated by the group of Brazilian experts with the purpose of guiding and enabling Brazilian clinical laboratories to adopt recommendations and to provide a common standard for national and international consensuses.

MAINBODY

Twenty Brazilian researchers and experts from universities and clinical laboratories representing the various geographical regions of the country participated in the meeting. Three main topics were discussed, namely the harmonization between the BCA guidelines and latest recommendations of the ICAP initiative, the adjustment of the terminology and report on HEp-2 patterns, and a reassessment of quality assurance parameters. For the three topics, our aim was to establish specific guidelines. All recommendations were based on consensus among participants. There was concrete progress in the adjustment of the BCA guidelines to match the ICAP guidelines. To a certain extent, this derives from the fact that ICAP recommendations were largely based on the algorithm and recommendations of the IV Brazilian ANA Consensus, as consistently recognized in the ICAP publications and presentations. However, although there is great overlap between the two Consensuses, there are some point divergences. These specific items were individually and extensively discussed, and it was acknowledged that in several points ICAP improved recommendations previously issued by the Brazilian ANA Consensus and these changes were readily implemented. Regarding some specific topics, the BCA panel of experts felt that the previously issued recommendations remained relevant and possibly will require further discussion with ICAP. The term anti-cell antibodies was adopted as the recommended designation, recognizing that the assay addresses antibodies against antigens in the nucleus and in other cell compartments. However, the acronym ANA HEp-2 was maintained due to historical and regulatory reasons. It was also signalized that the latest trend in ICAP is to adopt the term Indirect Immunofluorescent Assay on HEp-2 cell substrate (HEp-2 IIFA). In addition, the quality assurance strategies previously presented were ratified and emphasized.

CONCLUSION

The V BCA edition was successful in establishing an overall harmonization with the ICAP recommendations for interpretation of the HEp-2 IIFA test, pinpointing the perspectives in filling the remaining gaps between both initiatives.

Scurfy Mice Develop Features of Connective Tissue Disease Overlap Syndrome and Mixed Connective Tissue Disease in the Absence of Regulatory T Cells

Due to a missense mutation in the Foxp3 gene, scurfy mice are deficient in functional regulatory T cells (Treg). The consequent loss of peripheral tolerance manifests itself by fatal autoimmune mediated multi-organ disease. Previous studies have outlined the systemic inflammatory disease and demonstrated production of anti-nuclear antibodies (ANA) in scurfy mice. However, specific autoantibody targets remained to be defined. ANA are immunological markers for several connective tissue diseases (CTD) and target a large number of intracellular molecules. Therefore, we examined scurfy sera for the presence of different ANA specificities and further assessed the organ involvement in these animals. Indirect immunofluorescence was used as a screen for ANA in the sera of scurfy mice and dilutions of 1/100 were considered positive. Addressable laser bead immunoassays (ALBIA) were used to detect specific autoantibody targets. Subsequent histological tissue evaluation was verified by hematoxylin and eosin (H&E) staining. In our study, we observed that nearly all scurfy mice produced ANA. The most prevalent pattern in scurfy sera was nuclear coarse speckled, also known as the AC-5 pattern according to the International Consensus on ANA Patterns. U1-ribonucleoprotein (U1RNP) was found to be the most common target antigen recognized by autoantibodies in scurfy mice. Additionally, scurfy mice exhibited a mild myositis with histological characteristics similar to polymyositis/dermatomyositis. Myopathy-specific autoantibody profile revealed significantly increased levels of anti-SMN (survival of motor neuron) as well as anti-Gemin3 antibodies in scurfy sera. Overall, we demonstrate that the impaired peripheral tolerance in the absence of regulatory T cells in scurfy mice is associated with features of mixed connective tissue disease (MCTD). This includes, along with our previous findings, very high titers of anti-U1RNP antibodies and an inflammatory myopathy.

Anti-NT5c1A Autoantibodies as Biomarkers in Inclusion Body Myositis

Objective: Sporadic Inclusion Body Myositis (sIBM) is an inflammatory myopathy (IIM) without a specific diagnostic biomarker until autoantibodies to the cytosolic 5′-nucleotidase 1A (NT5c1A/Mup44) were reported. The objectives of our study were to determine the sensitivity and specificity of anti-NT5c1A for sIBM, demonstrate demographic, clinical and serological predictors for anti-NT5c1A positivity and determine if anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) staining on HEp-2 cells is a reliable screening method for anti-NT5c1A.

Methods: Sera from sIBM patients and controls were stored at −80°C until required for analysis. IgG antibodies to NT5c1A were detected by an addressable laser bead immunoassay (ALBIA) using a full-length human recombinant protein. Autoantibodies to other autoimmune myopathy antigens (Jo-1, OJ, TIF1y, PL-12, SAE, EJ, MDA5, PL7, SRP, NXP2, MI-2) were detected by line immunoassay (LIA), chemiluminescence immunoassay (CIA) or enzyme linked immunosorbent assay (ELISA) and ANA detected by IIF on HEp-2 substrate. Demographic, clinical and serological data were obtained by chart review.

Results: Forty-three patients with sIBM, 537 disease control patients with other autoimmune, degenerative and neuromuscular diseases, and 78 healthy controls were included. 48.8% (21/43) of sIBM patients were positive for anti-NT5c1A. The overall sensitivity, specificity, positive predictive value, and negative predictive value of anti-NT5c1A for sIBM were 0.49, 0.92, 0.29, and 0.96, respectively. Compared to sIBM, the frequency of anti-NT5c1A was lower in both the disease control group (8.8%, OR 0.10 [95%CI: 0.05–0.20], p < 0.0001) and in the apparently healthy control group (5.1%, OR 0.06 [95%CI: 0.02–0.18], p < 0.0001). In the univariable analysis, sIBM patients with more severe muscle weakness were more likely to be anti-NT5c1A positive (OR 4.10 [95% CI: 1.17, 14.33], p = 0.027), although this was not statistically significant (adjusted OR 4.30 [95% CI: 0.89, 20.76], p = 0.069) in the multivariable analysis. The ANA of sIBM sera did not demonstrate a consistent IIF pattern associated with anti-NT5c1A.

Conclusions: Anti-NT5c1A has moderate sensitivity and high specificity for sIBM using ALBIA. The presence of anti-NT5c1A antibodies may be associated with muscle weakness. Anti-NT5c1A antibodies were not associated with a specific IIF staining pattern, hence screening using HEp-2 substrate is unlikely to be a useful predictor for presence of these autoantibodies.

Clinical relevance of HEp-2 indirect immunofluorescent patterns: the International Consensus on ANA patterns (ICAP) perspective

The indirect immunofluorescence assay (IIFA) on HEp-2 cells is widely used for detection of antinuclear antibodies (ANA). The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases. However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s). The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells. The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns. In the current paper, the ICAP consensus is presented on the clinical relevance of the 29 distinct HEp-2 IIFA patterns. This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing. The discussion includes how this information may benefit the clinicians in daily practice and how the knowledge can be used to further improve diagnostic and classification criteria.

Interstitial lung disease and inflammatory myopathy in antisynthetase syndrome with PL-12 antibody

We report the case of an 80-year-old Caucasian man with PL-12 antibody positive antisynthetase syndrome. He presented with progressive dyspnoea and weight loss, later developing dysphagia, mild proximal muscle weakness and mild sicca symptoms. Investigations revealed interstitial lung disease, inflammatory myopathy and an immunology profile consistent with PL-12 antisynthetase syndrome. Prednisolone and cyclophosphamide resulted in a significant improvement of all his symptoms.

Bench to bedside review of myositis autoantibodies

Idiopathic inflammatory myopathies represent a heterogeneous group of autoimmune diseases with systemic involvement. Even though numerous specific autoantibodies have been recognized, they have not been included, with the only exception of anti-Jo-1, into the 2017 Classification Criteria, thus perpetuating a clinical-serologic gap. The lack of homogeneous grouping based on the antibody profile deeply impacts the diagnostic approach, therapeutic choices and prognostic stratification of these patients. This review is intended to highlight the comprehensive scenario regarding myositis-related autoantibodies, from the molecular characterization and biological significance to target antigens, from the detection tools, with a special focus on immunofluorescence patterns on HEp-2 cells, to their relative prevalence and ethnic diversity, from the clinical presentation to prognosis. If, on the one hand, a notable body of literature is present, on the other data are fragmented, retrospectively based and collected from small case series, so that they do not sufficiently support the decision-making process (i.e. therapeutic approach) into the clinics.

Bicaudal D2 is a novel autoantibody target in systemic sclerosis that shares a key epitope with CENP-A but has a distinct clinical phenotype

We studied the clinical correlations and epitopes of autoantibodies directed to a novel autoantigen, Bicaudal D (BICD2), in systemic sclerosis (SSc) and reviewed its relationship to centromere protein A (CENP-A). 451 SSc sera were tested for anti-BICD2 using a paramagnetic bead immunoassay and then univariate and multivariate logistic regression was used to study the association between anti-BICD2 and demographic and clinical parameters as well as other SSc-related autoantibodies. Epitope mapping was performed on solid phase matrices. 25.7% (116/451) SSc sera were anti-BICD2 positive, of which 19.0% had single specificity anti-BICD2 and 81.0% had other autoantibodies, notably anti-CENP (83/94; 88.3%). Compared to anti-BICD2 negative subjects (335/451), single specificity anti-BICD2 subjects were more likely to have an inflammatory myopathy (IM; 31.8% vs. 9.6%, p=.004) and interstitial lung disease (ILD; 52.4% vs. 29.0%, p=.024). Epitope mapping revealed a serine- and proline-rich nonapeptide SPSPGSSLP comprising amino acids 606-614 of BICD2, shared with CENP-A but not CENP-B. We observed that autoantibodies to BICD2 represent a new biomarker as they were detected in patients without other SSc-specific autoantibodies and were the second most common autoantibody identified in this SSc cohort. Our data indicate that the major cross-reactive epitope is associated with anti-CENP-A but, unlike anti-CENP, single specificity anti-BICD2 antibodies associate with ILD and IM.

A Comprehensive Overview on Myositis-Specific Antibodies: New and Old Biomarkers in Idiopathic Inflammatory Myopathy

Autoantibodies specific for idiopathic inflammatory myopathy (myositis-specific autoantibodies (MSAs)) are clinically useful biomarkers to help the diagnosis of polymyositis/dermatomyositis (PM/DM). Many of these are also associated with a unique clinical subset of PM/DM, making them useful in predicting and monitoring certain clinical manifestations. Classic MSAs known for over 30 years include antibodies to Jo-1 (histidyl transfer RNA (tRNA) synthetase) and other aminoacyl tRNA synthetases (ARS), anti-Mi-2, and anti-signal recognition particle (SRP). Anti-Jo-1 is the first autoantibodies to ARS detected in 15-25 % of patients. In addition to anti-Jo-1, antibodies to seven other aminoacyl tRNA synthetases (ARS) have been reported with prevalence, usually 1-5 % or lower. Patients with any anti-ARS antibodies are associated with anti-synthetase syndrome characterized by myositis, interstitial lung disease (ILD), arthritis, Raynaud's phenomenon, and others. Several recent studies suggested heterogeneity in clinical features among different anti-ARS antibody-positive patients and anti-ARS may also be found in idiopathic ILD without myositis. Anti-Mi-2 is a classic marker for DM and associated with good response to steroid treatment and good prognosis. Anti-SRP is specific for PM and associated with treatment-resistant myopathy histologically characterized as necrotizing myopathy. In addition to classic MSAs, several new autoantibodies with strong clinical significance have been described in DM. Antibodies to transcription intermediary factor 1γ/α (TIF1γ/α, p155/140) are frequently found in DM associated with malignancy while anti-melanoma differentiation-associated gene 5 (MDA5; CADM140) are associated with clinically amyopathic DM (CADM) complicated by rapidly progressive ILD. Also, anti-MJ/nuclear matrix protein 2 (NXP-2) and anti-small ubiquitin-like modifier-1 (SUMO-1) activating enzyme (SAE) are recognized as new DM-specific autoantibodies. Addition of these new antibodies to clinical practice in the future will help in making earlier and more accurate diagnoses and better management for patients.

Report of the First International Consensus on Standardized Nomenclature of Antinuclear Antibody HEp-2 Cell Patterns 2014-2015

During the 12th International Workshop on Autoantibodies and Autoimmunity held in Sao Paulo, Brazil, on August 28, 2014, a full day session was devoted to establishing a consensus on the nomenclature of staining patterns observed in the antinuclear antibody (ANA) indirect immunofluorescence test on HEp-2 cells. The current report summarizes the collective agreements with input from the host Brazilian and international communities that represented research, clinical, and diagnostic service laboratories. Patterns are categorized in three major groups (nuclear, cytoplasmic, and mitotic patterns) and each pattern has been defined and described in detail. The consensus nomenclature and representative patterns are made available online at the international consensus on antinuclear antibody pattern (ICAP) website (www.ANApatterns.org). To facilitate continuous improvement and input, specific comments on ICAP are encouraged and these will be discussed in subsequent ICAP meetings. The ultimate goal with the establishment of the ICAP is to promote harmonization and understanding of autoantibody test nomenclature, as well as interpretation guidelines for ANA testing, thereby optimizing usage in patient care.

Report of the First International Consensus on Standardized Nomenclature of Antinuclear Antibody HEp-2 Cell Patterns 2014-2015

During the 12th International Workshop on Autoantibodies and Autoimmunity held in Sao Paulo, Brazil, on August 28, 2014, a full day session was devoted to establishing a consensus on the nomenclature of staining patterns observed in the antinuclear antibody (ANA) indirect immunofluorescence test on HEp-2 cells. The current report summarizes the collective agreements with input from the host Brazilian and international communities that represented research, clinical, and diagnostic service laboratories. Patterns are categorized in three major groups (nuclear, cytoplasmic, and mitotic patterns) and each pattern has been defined and described in detail. The consensus nomenclature and representative patterns are made available online at the international consensus on antinuclear antibody pattern (ICAP) website (www.ANApatterns.org). To facilitate continuous improvement and input, specific comments on ICAP are encouraged and these will be discussed in subsequent ICAP meetings. The ultimate goal with the establishment of the ICAP is to promote harmonization and understanding of autoantibody test nomenclature, as well as interpretation guidelines for ANA testing, thereby optimizing usage in patient care.

Update: biomarkers for idiopathic inflammatory myopathies

PURPOSE OF REVIEW

Establishing diagnoses and distinguishing active disease from chronic injury remain significant clinical challenges in idiopathic inflammatory myopathies (IIM). Recent 'discovery' approaches utilizing novel genomic and proteomic techniques have revealed candidate molecular biomarkers to augment clinical and classical histological data.

RECENT FINDINGS

Whole blood and serum Type 1 interferons (IFN-1) and IFN-1 inducible genes are gaining traction as disease biomarkers in IIM. IFNβ is emerging as a disease activity marker specifically for dermatomyositis. Recently, molecules associated with innate immune-cell function, including TLR-3, high mobility group box (HMGB)-1, B7 Homolog 1, S100A4, and resistin have been detected in tissues of dermatomyositis patients. Serum Interleukin-17 (IL-17) and IL-23 correlate with active disease in early IIM. Antibodies recognizing the Survival Motor Neuron complex have been newly identified in a subset of patients with polymyositis. Protein aggregates are potential disease activity sensors for inclusion body myositis. Skin and lung harbor potential biomarkers for IIM.

SUMMARY

Recent advances in understanding the pathogenesis of IIM have led to discovery of molecules that are candidate biomarkers of disease activity. Type 1 interferon and myeloid-cell signatures are leading candidate markers for use in IIM activity monitoring.

Common pathways of autoimmune inflammatory myopathies and genetic neuromuscular disorders

It has been shown that many hereditary motor neuron diseases are caused by mutation of RNA processing enzymes. Survival of motor neuron 1 (SMN1) is well-known as a causative gene for spinal muscular atrophy (SMA) and mutations of glycyl- and tyrosyl-tRNA synthetases are identified as a cause of distal SMA and Charcot-Marie-Tooth disease. Why and how the dysfunction of these ubiquitously expressed genes involved in RNA processing can cause a specific neurological disorder is not well understood. Interestingly, SMN complex has been identified recently as a new target of autoantibodies in polymyositis (PM). Autoantibodies in systemic rheumatic diseases are clinically useful biomarkers associated with a particular diagnosis, subset of a disease, or certain clinical characteristics. Many autoantibodies produced in patients with polymyositis/dermatomyositis (PM/DM) target RNA-protein complexes such as aminoacyl tRNA synthetases. It is interesting to note these same RNA-protein complexes recognized by autoantibodies in PM/DM are also responsible for genetic neuromuscular disease. Certain RNA-protein complexes are also targets of autoantibodies in paraneoplastic neurological disorders. Thus, there are several interesting associations between RNA-processing enzymes and neuromuscular disorders. Although pathogenetic roles of autoantibodies to intracellular antigens are generally considered unlikely, understanding the mechanisms of antigen selection in a particular disease and specific neurological symptoms caused by disruption of ubiquitous RNA-processing enzyme may help identify a common path in genetic neuromuscular disorders and autoimmunity in inflammatory myopathies.

Missing links in high quality diagnostics of inflammatory systemic rheumatic diseases: It is all about the patient!

The aim of this review is to focus attention on high quality diagnostics of systemic inflammatory rheumatic diseases. Though many steps in the diagnostic process from the first visit in a doctor’s office till a final diagnosis have been established a lot of things still must be done to improve quality assurance and secure fast and safe transmission of data from one step to the next. Some procedures inherent in early high quality diagnostics need to be worked out. A number of elements can be improved, some stumble stones can be removed, and a tighter collaboration between actors at different levels in the line of action in clinical and laboratory medicine can be organized. Several proposals have been made by international working groups such as the IUIS International Autoantibody Standardization Committee, and the EASI steering group in collaboration with their national EASI teams. Practical exercises carried out for more than three decades by the European Consensus Finding Study Group have proven to very useful. The review points at several principles worked out by these international expert groups can be useful in actual daily practice also in rheumatology. The hope is that the presentation will give rise to a continued discussion on how to link different parts of the diagnostic process together and strengthen collaboration between all teams involved in the diagnostic chain. The ultimate measure of success will be better clinical outcomes for patients and increased satisfaction in their families.