Corrigendum: Adult-Onset Anti-Citrullinated Peptide Antibody-Negative Destructive Rheumatoid Arthritis Is Characterized by a Disease-Specific CD8+ T Lymphocyte Signature.

[This corrects the article DOI: 10.3389/fimmu.2020.578848.].

Is seronegative rheumatoid arthritis true rheumatoid arthritis? A nationwide cohort study.

OBJECTIVES: The classification of seronegative arthritides can be challenging. Our aim was to examine the incidence of SpA diagnosis among patients initially diagnosed as seronegative RA. METHODS: Using nationwide Finnish registers from social insurance institutions, we identified all adult patients who were diagnosed with incident seronegative RA [International Classification of Diseases (ICD)-10 code M06] from 1 January 2000 to 31 December 2014. The patients whose diagnoses subsequently changed to the ICD-10 codes of SpA (M07, M45, M46, K50 and K51) were identified in the national care register, until 31 December 2016. RESULTS: A total of 9784 adult seronegative RA patients were identified. Of these, 564 patients had their diagnosis subsequently changed to SpA: 275 (48.7%) patients with PsA, 245 (43.4%) patients with axial SpA and 44 (7.8%) patients with diagnoses related to IBD. The cumulative incidence of SpA diagnoses in 15 years was 10.4% (95% CI 8.9, 12.1) and 8.1% (95% CI 7.1, 9.3) in men and women, respectively. CONCLUSION: This study calls for vigilance in seronegative RA patients, especially those with more atypical presentations, since the diagnosis could change. The possibility of SpA diagnosis should be considered and specifically looked for, as this could impact on management and response to treatment.

Adult-Onset Anti-Citrullinated Peptide Antibody-Negative Destructive Rheumatoid Arthritis Is Characterized by a Disease-Specific CD8+ T Lymphocyte Signature.

Rheumatoid arthritis (RA) is a complex autoimmune disease targeting synovial joints. Traditionally, RA is divided into seropositive (SP) and seronegative (SN) disease forms, the latter consisting of an array of unrelated diseases with joint involvement. Recently, we described a severe form of SN-RA that associates with characteristic joint destruction. Here, we sought biological characteristics to differentiate this rare but aggressive anti-citrullinated peptide antibody-negative destructive RA (CND-RA) from early seropositive (SP-RA) and seronegative rheumatoid arthritis (SN-RA). We also aimed to study cytotoxic CD8+ lymphocytes in autoimmune arthritis. CND-RA, SP-RA and SN-RA were compared to healthy controls to reveal differences in T-cell receptor beta (TCRß) repertoire, cytokine levels and autoantibody repertoires. Whole-exome sequencing (WES) followed by single-cell RNA-sequencing (sc-RNA-seq) was performed to study somatic mutations in a clonally expanded CD8+ lymphocyte population in an index patient. A unique TCRß signature was detected in CND-RA patients. In addition, CND-RA patients expressed higher levels of the bone destruction-associated TNFSF14 cytokine. Blood IgG repertoire from CND-RA patients recognized fewer endogenous proteins than SP-RA patients' repertoires. Using WES, we detected a stable mutation profile in the clonally expanded CD8+ T-cell population characterized by cytotoxic gene expression signature discovered by sc-RNA-sequencing. Our results identify CND-RA as an independent RA subset and reveal a CND-RA specific TCR signature in the CD8+ lymphocytes. Improved classification of seronegative RA patients underlines the heterogeneity of RA and also, facilitates development of improved therapeutic options for the treatment resistant patients.

Prevalence of calcium pyrophosphate deposition disease in a cohort of patients diagnosed with seronegative rheumatoid arthritis.

OBJECTIVES: We aimed to characterise the clinical and radiographical phenotype of calcium pyrophosphate dihydrate deposition (CPPD) disease in patients initially diagnosed with seronegative RA, and to increase the awareness that CPPD disease can be falsely diagnosed as seronegative rheumatoid arthritis (RA). METHODS: Altogether 435 early seronegative RA patients were clinically diagnosed in a single rheumatology centre and scheduled for a 10-year follow-up. All clinical data were collected and reviewed. CPPD-related arthritis was suspected if a patient had typical radiographical findings and suitable clinical pattern of CPPD or calcium pyrophosphate crystals were found in the synovial fluid. These patients are the subjects of this study. RESULTS: Among 435 seronegative RA patients, 17 patients (3.9%) (baseline mean age 71.2 years, 82% women) with CPPD disease were identified. CPPD resembling clinical patterns in these patients were: chronic CPP crystal inflammatory arthritis (9 patients), acute CPP crystal arthritis (6 patients) and OA with CPPD (2 patients). All had typical radiographical findings of CPPD: Chondrocalcinosis (CC) of triangular fibrocartilage (17 patients [100%]), CC of knee (9 patients [53%]), CC or narrowing of metacarpophalangeal joints (7 patients [41.2%]), CC of metatarsophalangeal joints (4 patients [23.5%]), CC of symphysis pubis (1 patient [5.8%]), CC of glenohumeral joint (1 patient [5.8%]) and scapholunate advanced collapse (5 patients [29.4%]). None of these patients developed typical RA-like erosions. CONCLUSIONS: CPPD disease can mimic seronegative RA at baseline and is important in the differential diagnosis of seronegative arthritis at baseline and during follow-up. The prevalence of CPPD patients in our early seronegative RA patients was 3.9%, the percentage was 7.0% among patients ≥60 years at baseline.

Does early seronegative arthritis develop into rheumatoid arthritis? A 10-year observational study.

OBJECTIVES: To investigate the 10-year clinical course of patients with seronegative arthritis with the emphasis of reclassification of diagnoses when applicable. METHODS: A total of 1030 patients including 435 seronegative cases were classified as early RA in 1997-2005 at Jyväskylä Rheumatology Centre and prospectively scheduled for a ten-year follow-up. Clinical data from the follow-up visits and the case-reports until and including the 10-year visit or death, whichever happened earlier, were retrospectively collected and reviewed with re-classification of the cases when applicable. Descriptive statistics were used. RESULTS: Among the 435 seronegative cases (69 % women, baseline mean age was 59 years), 13 (13/435 [3%]) could be reclassified as seropositive or erosive RA: 4 turned seropositive (2 for ACPA and 2 for RF [> 2x reference level]) and 9 developed erosions typical for RA. Reclassification revealed 68 (16%) cases of polymyalgia rheumatica, 46 (11%) psoriatic arthritis, 45 (10%) osteoarthritis, 38 (8.7%) spondyloarthritis, 15 (3.4%) plausible reactive arthritis, 10 (2.3%) gout, 17 (3.9%) pseudogout, 6 (1.4%) paraneoplastic arthritis, 6 (1.4%) juvenile arthritis, 2 (0.5%) haemochromatosis, 3 (0.7%) ankylosing spondylitis, 2 (0.5%) giant cell arteritis, and 8 miscellaneous diagnoses. The other 140 patients (32%) could not be reclassified in any clear-cut diagnosis and had features of transient arthritis (n=41), seronegative spondyloarthritis (n=47), while 49 remained unspecified. CONCLUSIONS: Over a 10-year follow-up period, reclassification revealed significant heterogeneity in the diagnosis of seronegative RA. Therefore, seronegative arthritis should not be studied as a homogenous entity.

Survival and safety of infliximab bio-original and infliximab biosimilar (CT-P13) in usual rheumatology care.

OBJECTIVES: Reports to-date indicate similarity between infliximab biosimilar (IB) and infliximab bio-original (IO) in clinical efficacy and safety. This study examines the survival of IB and IO using routinely collected data over a 2-year period. METHODS: Routinely collected clinical data inputted directly in an electronic database at a large rheumatology centre were analysed. Adult patients taking IO or IB for any rheumatological diagnosis were included. Kaplan-Meier survival analyses were used to examine IB and IO survival, with a sub-group analysis among those starting infliximab from 2008 onwards. RESULTS: Out of 395 patients analysed, 53% (n=209) were female; the majority had rheumatoid arthritis (31%) followed by spondyloarthritis (28%). Ninety-nine patients had IB as the first infliximab drug. Patients who started on IB vs. IO as their first infliximab product, had better survival over the first 2 years (log rank=0.001). Discontinuation due to inefficacy was much commoner in IO versus IB users (18 vs. 5%). In patients switching from IO to IB, drug survival was better versus those receiving IB as the first infliximab drug (log rank=0.073). CONCLUSIONS: IB was well-tolerated and comparable to IO, with no additional safety signals identified. The results suggest superior survival of IB over IO over the first 2 years.