Review of systemic sclerosis and antineutrophil cytoplasmic antibody vasculitis overlap: Using autoantibodies for a personalised medicine approach

Early skeletal muscle manifestations in polyarteritis nodosa and ANCA-associated vasculitis

Skeletal muscle involvement is common in patients with small- and medium-sized vasculitis, particularly polyarteritis nodosa (PAN) and antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Despite being not included in the standard classification criteria for PAN and AAV, skeletal muscle involvement is an important clinical indicator, particularly when vasculitic myopathy is the only pathological evidence in the absence of other organ involvement. Herein, we comprehensively reviewed and compared the clinical features of 71 and 135 patients with PAN and AAV, respectively, with skeletal muscle involvement at the time of disease onset. Most patients with PAN and AAV exhibited skeletal muscle involvement, often characterized by myalgia and occasional muscular weakness, predominantly in the lower extremities. Myalgia and weakness were observed more frequently in the distal lower extremities in patients with PAN than in those with AAV. In contrast, skeletal muscle involvement tended to exhibit a more dispersed distribution across all four extremities in those with AAV. Muscle magnetic resonance imaging T2-weighted and short-tau inversion recovery sequences can effectively identify hyperintense areas attributed to hypervascularity of affected muscle tissues and serve as a sensitive and useful modality for visually determining the suitable biopsy site. >90% of patients with PAN and AAV demonstrated perivascular inflammation in their affected muscle tissues, whereas fibrinoid necrosis of the vessel walls was reported in two-thirds of patients. Serum creatine kinase (CK) levels were within the normal range in approximately 80% of patients presenting with skeletal muscle involvement in PAN and AAV. Furthermore, muscle fiber damage was milder in patients with skeletal muscle involvement in PAN and AAV than those with idiopathic inflammatory myositis. Meanwhile, serum CK levels were elevated in 65-85% of patients with PAN and AAV who had myofiber necrosis and degeneration in the affected muscles. Most patients with PAN and AAV showed improvement in skeletal muscle involvement following glucocorticoids (GCs) administration; however, relapse was observed in some patients during the tapering of GCs. In summary, skeletal muscle involvement is a potential indicator for establishing PAN and AAV diagnoses during the early phases of the disease.

Incidence of Systemic Vasculitis and Clinical Outcomes in Systemic Sclerosis: 2-Years Follow-Up of Asymptomatic Positive for Anti-Neutrophilic Cytoplasmic Antibody

Purpose

Anti-neutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV) overlap with systemic sclerosis (SSc) is uncommon. We aimed to determine the incidence of AAV and define clinical outcomes relevant to asymptomatic screening positive for ANCA in SSc after 2 years of follow-up.

Patients and Methods

The study was a cohort study of 185 Thai adult SSc patients testing for ANCA and having a 2-year follow-up at the Scleroderma Clinic, Khon Kaen University, Thailand. The incidence of AAV and outcomes of those who tested positive for ANCA were evaluated.

Results

A total of 185 SSc patients were tested for ANCA, of whom 21.6% were positive for either cytoplasmic ANCA, perinuclear ANCA (p-ANCA), anti-myeloperoxidase (anti-MPO), or anti-proteinase3 antibody. Only one 52-year-old female patient with dcSSc, negative for initial ANCA test, developed AAV (microscopic polyangiitis) 7 months after the first ANCA test for an incidence of AAV of 0.27 per 100-person-years (95% CI 0.01-1.5). She was positive for p-ANCA and anti-MPO. Eight of those who had an initial test were positive for ANCA and underwent a repeated test. Only two cases persisted as positive for ANCA (1 anti-MPO and 1 anti-PR3) and had no clinicals suspicious of vasculitis. Four cases that had ANCA turned to a negative result.

Conclusion

AAV is a rare complication in SSc, so ANCA may not have any role as a screening test for AAV as it cannot predict the development of AAV in SSc. We suggest testing for ANCA only in SSc patients with clinicals suspicious of AAV.

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.