Association of HLA-class II alleles with risk of relapse in myeloperoxidase-antineutrophil cytoplasmic antibody positive vasculitis in the Japanese population.

Background: Disease relapse remains a major problem in the management of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In European populations, HLA-DPB1*04:01 is associated with both susceptibility and relapse risk in proteinase 3-ANCA positive AAV. In a Japanese population, we previously reported an association between HLA-DRB1*09:01 and DQB1*03:03 with susceptibility to, and DRB1*13:02 with protection from, myeloperoxidase-ANCA positive AAV (MPO-AAV). Subsequently, the association of DQA1*03:02, which is in strong linkage disequilibrium with DRB1*09:01 and DQB1*03:03, with MPO-AAV susceptibility was reported in a Chinese population. However, an association between these alleles and risk of relapse has not yet been reported. Here, we examined whether HLA-class II is associated with the risk of relapse in MPO-AAV. Methods: First, the association of HLA-DQA1*03:02 with susceptibility to MPO-AAV and microscopic polyangiitis (MPA) and its relationship with previously reported DRB1*09:01 and DQB1*03:03 were examined in 440 Japanese patients and 779 healthy controls. Next, the association with risk of relapse was analyzed in 199 MPO-ANCA positive, PR3-ANCA negative patients enrolled in previously reported cohort studies on remission induction therapy. Uncorrected P values (Puncorr) were corrected for multiple comparisons in each analysis using the false discovery rate method. Results: The association of DQA1*03:02 with susceptibility to MPO-AAV and MPA was confirmed in a Japanese population (MPO-AAV: Puncorr=5.8x10-7, odds ratio [OR] 1.74, 95% confidence interval [CI] 1.40-2.16, MPA: Puncorr=1.1x10-5, OR 1.71, 95%CI 1.34-2.17). DQA1*03:02 was in strong linkage disequilibrium with DRB1*09:01 and DQB1*03:03, and the causal allele could not be determined using conditional logistic regression analysis. Relapse-free survival was shorter with nominal significance in carriers of DRB1*09:01 (Puncorr=0.049, Q=0.42, hazard ratio [HR]:1.87), DQA1*03:02 (Puncorr=0.020, Q=0.22, HR:2.11) and DQB1*03:03 (Puncorr=0.043, Q=0.48, HR:1.91) than in non-carriers in the log-rank test. Conversely, serine carriers at position 13 of HLA-DRß1 (HLA-DRß1_13S), including DRB1*13:02 carriers, showed longer relapse-free survival with nominal significance (Puncorr=0.010, Q=0.42, HR:0.31). By combining DQA1*03:02 and HLA-DRß1_13S, a significant difference was detected between groups with the highest and lowest risk for relapse (Puncorr=0.0055, Q=0.033, HR:4.02). Conclusion: HLA-class II is associated not only with susceptibility to MPO-AAV but also with risk of relapse in the Japanese population.

Comparison of radiological characteristics between diffuse idiopathic skeletal hyperostosis and ankylosing spondylitis: a multicenter study.

To evaluate the radiological differences between diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS) using whole spine computed tomography (CT), including the spine and sacroiliac joint (SIJ). The ossification and bridging of spinal ligament and fusion of the facet joint and SIJ were evaluated in 111 patients who were diagnosed with DISH and 27 patients with AS on the whole spine CT. The number of anterior bridging and shape of bridging (candle-wax-type/ smooth-type) were also evaluated. We further evaluated patients with DISH and AS by matching their age and sex. Complete SIJ fusion was more common in AS, whereas anterior and posterior bony bridging around SIJ was more common in DISH. However, 63% of patients with DISH had a partial or complete fusion. In spinal anterior bony bridging, the majority of patients with AS had the smooth-type, whereas those with DISH had the candle-wax-type. However, some of the patients with DISH (11%) had smooth-type. Intervertebral facet joint fusion is more common in AS. The number of anterior spinal bony bridging was greater in AS than in DISH, especially in the lumbar spine. These results are useful in differentiating DISH from AS and should therefore be considered when making a diagnosis.

A multicentre study of clinical features and HLA typing in Japanese patients with ankylosing spondylitis.

OBJECTIVES: Due to the low prevalence of HLA-B27 and ankylosing spondylitis (AS) in Japan, rheumatologists have little experience with AS. We conducted a multicentre study to identify the characteristics and frequency of HLA-B types. METHODS: We analysed epidemiological and clinical data, blood tests, spine radiographs, and HLA-B types in Japanese AS patients. RESULTS: We evaluated 111 AS patients, predominantly men (82.9%). The mean age, disease onset, diagnosis, and time from onset to diagnosis were 43.7, 24.2, 36.0, and 11.6 years, respectively. Inflammatory low back pain was found in 96 cases (86.5%); peripheral arthritis in 59 (53.2%), enthesitis in 35 (31.5%), and dactylitis in 6 (5.4%). Extra-articular symptoms included uveitis, psoriasis, and inflammatory bowel disease in 41 (36.9%), 1 (0.9%), and 5 (4.5%) cases, respectively. HLA-B27 was positive in 83 cases (74.8%; odds ratio, 1146.0); and HLA-B48 in 9 (8.1%; odds ratio, 3.0). HLA-B27-positive patients were younger at onset and had a shorter diagnostic delay. CONCLUSIONS: AS clinical symptoms were almost the same as other countries except for the low coexistence of psoriasis. HLA-B27 positivity in Japanese patients was 78%. HLA-B27-positive patients were younger and diagnosed earlier. In addition to HLA-B27, a relationship with HLA-B48 was suggested.

Brodalumab, an anti-interleukin-17 receptor A monoclonal antibody, in axial spondyloarthritis: 68-week results from a phase 3 study.

OBJECTIVE: To evaluate the long-term efficacy and safety of brodalumab, a fully human anti-interleukin-17 receptor A monoclonal antibody, in patients with axial spondyloarthritis (axSpA). METHODS: Patients receiving subcutaneous brodalumab 210 mg during the 16-week double-blind period of this multicentre, phase 3 study conducted across Japan, Korea and Taiwan continued the same during the 52-week open-label extension, whereas patients receiving placebo switched to brodalumab 210 mg at week 16. Efficacy [Assessment of SpondyloArthritis International Society (ASAS) 40 and ASAS 20 response rates; change from baseline in AS Disease Activity Score using CRP (ASDAS-CRP)] and safety were evaluated. RESULTS: Overall, 145 patients (brodalumab, n = 77; placebo, n = 68) received brodalumab during the open-label extension. ASAS 40 response rates (95% CI) of 56.3% (44.7%, 67.3%) and 57.4% (44.1%, 70.0%) were achieved in the brodalumab and placebo groups, respectively, at week 68. ASAS 20 response rates (95% CI) achieved at week 68 in both treatment groups were similar [brodalumab, 71.3% (60.0%, 80.8%); placebo, 78.7% (66.3%, 88.1%)]. The least squares mean change (95% CI) in ASDAS-CRP at week 68 suggested a clinically important improvement (change, ≥1.1) in both treatment groups [brodalumab, -1.528 (-1.737, -1.319); placebo, -1.586 (-1.815, -1.357)]. The exposure-adjusted event rates (per 100 patient-years) for treatment-emergent adverse events (TEAEs) and drug-related TEAEs were 255.9 and 147.9, respectively; nasopharyngitis (35.6) and upper respiratory tract infection (14.7) were the most common TEAEs. CONCLUSIONS: Brodalumab demonstrated sustained efficacy and a consistent safety profile in patients with axSpA over 68 weeks. STUDY REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT02985983.

Axial Spondyloarthritis in Japan.

PURPOSE OF REVIEW: The differences in the epidemiology and management of patients with axial spondyloarthritis (axSpA) among regions and countries largely depend on the positivity of human leukocyte antigen (HLA)-B27 and the health care system. This review article focused on axSpA in Japan, where the prevalence of HLA-B27 is extremely low (0.3%) and the universal health insurance system typically provides a 70% or more copayment by the government. RECENT FINDINGS: A nationwide survey was conducted in Japan in 2018, which estimated that there were 3200 patients (95% confidence interval [CI]: 2400-3900) with ankylosing spondylitis (AS), a term interchangeable with radiographic axSpA (r-axSpA), and 800 patients (95% CI: 530-1100) had non-radiographic (nr)-axSpA. These data indicate a prevalence of 2.6/100,000 or 0.0026% for AS and 0.6/100,000 or 0.0006% for nr-axSpA. Patients with AS, but not those with nr-axSpA, are designated as suffering from intractable diseases in Japan; thus, their medical expenses are reduced by grant under the Act on Medical Care for Patients with Intractable Diseases. As of February 2022, infliximab, adalimumab, secukinumab, ixekizumab, and brodalumab have been approved for AS, and secukinumab, ixekizumab, and brodalumab have been approved for nr-axSpA. An algorithm for nr-axSpA in Japan has been developed for the proper diagnosis and use of these therapeutic agents. A low prevalence of axSpA, especially that of nr-axSpA, was found in Japan. Early referral and the resultant diagnosis and appropriate treatment of these patients by rheumatologists are crucial issues in Japan, as in other countries.

Reactive Arthritis After Intravesical Bacillus Calmette-Guérin Therapy.

ABSTRACT: Reactive arthritis (ReA) is a sterile arthritis that occurs in genetically predisposed individuals secondary to an extra-articular infection, usually of the gastrointestinal or genitourinary tract. Sterile arthritis associated with instillation of intravesical bacillus Calmette-Guérin (iBCG) therapy used for bladder cancer can also be included under ReA based on the pathogenic mechanism. Similar to spondyloarthritis, HLA-B27 positivity is a known contributor to the genetic susceptibility underlying iBCG-associated ReA. Other genetic factors, such as HLA-B39 and HLA-B51, especially in Japanese patients, can also be involved in the pathophysiology of iBCG-associated ReA. The frequencies of ReA- and ReA-related symptoms are slightly different between Japanese and Western studies. Proper understanding of possible complications, their epidemiology and pathogenesis, and their management is important for the rheumatologist when noting symptomatic patients using iBCG. Herein, we will review the most current information on ReA after iBCG therapy.

A nationwide questionnaire survey on the prevalence of ankylosing spondylitis and non-radiographic axial spondyloarthritis in Japan.

OBJECTIVE: This nationwide study aimed to reveal the prevalence of ankylosing spondylitis (AS), non-radiographic axial spondyloarthritis (nr-ax SpA), and the positivity rate of human leukocyte antigen (HLA) among such patients in Japan. METHODS: The first survey was conducted in 2221 randomly selected facilities (26.3%) in September 2018, where the patients with AS/nr-ax SpA were taken care of from January to December 2017. We estimated the total number of these patients using response and extraction rates. A second survey was conducted in 117 facilities (49.8%) to assess for HLA-B27 positivity rate and clinical features. RESULTS: The estimated total numbers of the patients with AS and nr-ax SpA were 3200 (95% confidence interval [CI]: 2400-3900) and 800 (530-1100), suggesting that the prevalence values of AS and nr-ax SpA in general population were 2.6/100,000 (0.0026%) and 0.6/100,000 (0.0006%), respectively. Although 55.5% (76/137) of patients with AS were HLA-B27-positive, those whose age of onset was estimated to be over 50 years tended to undergo less HLA-B27 testing. CONCLUSION: This study revealed the lower prevalence of AS/nr-ax SpA in Japan, compared to those in other countries. Further studies are required to reveal the association of HLA-B27 with the clinical features.

Clinical characteristics of non-radiographic versus radiographic axial spondyloarthritis in Asia and non-radiographic axial spondyloarthritis in other regions: results of the cross-sectional ASAS-COMOSPA study.

OBJECTIVES: To delineate characteristics of non-radiographic axial spondyloarthritis (nr-axSpA) in Asia versus non-Asian regions, and compare radiographic axSpA (r-axSpA) with nr-axSpA within Asia. METHODS: Data were collected from the Assessment of SpondyloArthritis international Society-COMOrbidities in SPondyloArthritis database. Categorising patients by region, we compared clinical characteristics between nr-axSpA from Asia vs elsewhere (Europe, the Americas and Africa). Within Asians, we additionally compared patient characteristics of those with nr-axSpA versus r-axSpA. RESULTS: Among 3984 SpA cases, 1094 were from Asian countries. Of 780 axSpA patients in Asia, 112 (14.4%) had nr-axSpA, less than in non-Asian countries (486/1997, 24.3%). Nr-axSpA patients in Asia were predominantly male (75.9% vs 47.1%), younger at onset (22.8 vs 27.8 years) and diagnosis (27.2 vs 34.5 years), and experienced less diagnostic delay (1.9 vs 2.9 years) compared with nr-axSpA in non-Asian countries. Nr-axSpA in Asia exhibited higher human leucocyte antigens-B27 prevalence (90.6% vs 61.9%), fewer peripheral SpA features (53.6% vs 66.3%) and similar extra-articular and comorbid disease rates compared with those with nr-axSpA in non-Asian countries. Disease activity, functional impairment and MRI sacroiliitis were less in nr-axSpA in Asia, with higher rates of non-steroidal anti-inflammatory drug response and less methotrexate and biological disease-modifying antirheumatic drugs use. Within Asia, r-axSpA showed higher disease activity and structural damage compared with nr-axSpA, with no differences in other features. CONCLUSION: Among axSpA, lower frequency of nr-axSpA was observed in Asia. Our results offer an opportunity to better understand clinical characteristics and optimise diagnostic strategies, such as ensuring access and availability of MRI resources for accurate diagnosis of nr-axSpA in Asia.

Expanding the spectrum of reactive arthritis (ReA): classic ReA and infection-related arthritis including poststreptococcal ReA, Poncet's disease, and iBCG-induced ReA.

Reactive arthritis (ReA) is a form of sterile arthritis that occurs secondary to an extra-articular infection in genetically predisposed individuals. The extra-articular infection is typically an infection of the gastrointestinal tract or genitourinary tract. Infection-related arthritis is a sterile arthritis associated with streptococcal tonsillitis, extra-articular tuberculosis, or intravesical instillation of bacillus Calmette-Guérin (iBCG) therapy for bladder cancer. These infection-related arthritis diagnoses are often grouped with ReA based on the pathogenic mechanism. However, the unique characteristics of these entities may be masked by a group classification. Therefore, we reviewed the clinical characteristics of classic ReA, poststreptococcal ReA, Poncet's disease, and iBCG-induced ReA. Considering the diversity in triggering microbes, infection sites, and frequency of HLA-B27, these are different disorders. However, the clinical symptoms and intracellular parasitism pathogenic mechanism among classic ReA and infection-related arthritis entities are similar. Therefore, poststreptococcal ReA, Poncet's disease, and iBCG-induced ReA could be included in the expanding spectrum of ReA, especially based on the pathogenic mechanism.

Efficacy and safety of brodalumab, an anti-IL17RA monoclonal antibody, in patients with axial spondyloarthritis: 16-week results from a randomised, placebo-controlled, phase 3 trial.

OBJECTIVE: To investigate the efficacy and safety of brodalumab, a fully human anti-interleukin-17 receptor A monoclonal antibody, in patients with axial spondyloarthritis (axSpA). METHODS: In a multicentre, placebo-controlled phase 3 study (NCT02985983) conducted at 48 sites across Japan, Korea and Taiwan, patients with axSpA were randomised 1:1 to receive subcutaneous brodalumab 210 mg (n=80) or placebo (n=79) at baseline, weeks 1 and 2 and every 2 weeks thereafter, during the 16-week double-blind period. The primary endpoint was the proportion of patients with Assessment of SpondyloArthritis International Society (ASAS) 40 response at week 16. Secondary endpoints included the proportion of patients with ASAS 20 response and change in Ankylosing Spondylitis Disease Activity Score using C-reactive protein (ASDAS-CRP) at week 16 and safety. RESULTS: ASAS 40 response rate (n/N; 95% CI) was 43.8% (35/80; 32.7, 55.3) with brodalumab vs 24.1% (19/79; 15.1, 35.0) with placebo (rate difference, 19.7% (5.3, 34.1); p=0.018 by stratified Cochran-Mantel-Haenszel test). ASAS 20 response rate (n/N; 95% CI) was 67.5% (54/80; 56.1, 77.6) vs 41.8% (33/79; 30.8, 53.4) and least squares mean change (95% CI) from baseline (brodalumab, 2.660; placebo, 2.716) in ASDAS-CRP was -1.127 (-1.322, -0.931) with brodalumab vs -0.672 (-0.872, -0.473) with placebo at week 16. Treatment-emergent adverse events were reported in 44 (55%) and 45 (57%) patients in the brodalumab and placebo groups, respectively. CONCLUSION: Brodalumab demonstrated a significant improvement at week 16 in patients with active axSpA. Safety of brodalumab was consistent with that reported in previous global/Japanese psoriasis studies.

Tonsillitis-Related Arthritis: Advanced Understandings of Tonsillitis and Sterile Inflammatory Arthritis.

A 49-year-old man developed acute aseptic arthritis of the nonmigratory and asymmetrical type in his knee, ankle, and bilateral metatarsal joints 13 days after treatment with antibiotics for acute tonsillitis. He was diagnosed with tonsillitis-related arthritis after other rheumatic diseases were ruled out. Treatment with salazosulfapyridine, methotrexate, and methylprednisolone for 3 months did not completely improve. Then, tonsillectomy was undertaken and arthritis rapidly improved. Finegoldia magna (previously Peptostreptococcus magnus) was cultured from the microabscesses of the resected tonsils. After outpatient follow-up, the patient did not experience a relapse of arthritis for more than 2.7 years without any treatment. Poststreptococcal reactive arthritis (PSRA) is well described. However, up to 40% of patients with tonsillitis-related arthritis did not demonstrate evidence of streptococcal infection. It is noted that tonsillectomy is necessary to remove the tonsillar microabscesses and eradicate bacterial infection of the tonsils, especially for patients with a prolonged and/or recurrent course of PSRA and/or tonsillitis-related arthritis.

Non-radiographic axial spondyloarthritis.

Non-radiographic axial spondyloarthritis (nr-axSpA) is a subgroup of axial spondyloarthritis (axSpA) without fulfilling the modified New York criteria of sacroiliac joint radiographs for ankylosing spondylitis (AS). AS and nr-axSpA share various demographic and clinical features and disease burden, although sex and objective inflammatory findings such as elevated serum C-reactive protein level are slightly different between AS and nr-axSpA. Recently, diagnostic guidance for nr-axSpA in Japan was proposed for epidemiological studies of a population with a low prevalence of HLA-B27 positivity and the use of molecular targeted agents suitable for the unique medical care system in Japan. A biological agent targeting interleukin-17 was approved for nr-axSpA by the Pharmaceutical and Medical Devices Agency (PMDA) in August 2020. Some other biological agents will be also available for Japanese patients with nr-axSpA in the near future.

Clinical characteristics, the diagnostic criteria and management recommendation of otitis media with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (OMAAV) proposed by Japan Otological Society.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a form of necrotizing vasculitis with few or no immune deposits. It primarily affects small and medium blood vessels. AAV is classified into three categories, granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangitis (EGPA), and two major ANCAs, proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA are involved in their pathogenesis. Intractable otitis media frequently occurs in patients with GPA, MPA or EGPA, although all patients show similar clinical features, regardless of the type of AAV. Furthermore, approximately 15% patients with otitis media caused by AAV do not show ANCA positivity, histopathological evidence, or any other AAV-related lesions at the initial visit; therefore, these patients do not fulfill the ordinary diagnostic criteria for systemic AAV. Thus, we first proposed that this condition could be categorized as "otitis media with AAV (OMAAV)". Subsequently, the Japanese Otological Society (JOS) conducted a nationwide survey between December 2013 and February 2014 and identified 297 patients with OMAAV. The survey revealed that OMAAV is a disease that initially occurs in the middle ear and subsequently spreads to other organs such as the lungs and kidneys, with eventual involvement of all body organs. Severe sequelae such as facial palsy, hypertrophic pachymeningitis, complete deafness, and subarachnoid hemorrhage resulting in death can also occur. In this review, we introduce the clinical features, diagnostic criteria, and treatment strategies recommended by JOS for early diagnosis and treatment of OMAAV.

Association of TERT and DSP variants with microscopic polyangiitis and myeloperoxidase-ANCA positive vasculitis in a Japanese population: a genetic association study.

BACKGROUND: Interstitial lung disease (ILD) is a severe complication with poor prognosis in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Prevalence of AAV-associated ILD (AAV-ILD) in Japan is considerably higher than that in Europe. Recently, we reported that a MUC5B variant rs35705950, the strongest susceptibility variant to idiopathic pulmonary fibrosis (IPF), was strikingly increased in AAV-ILD patients but not in AAV patients without ILD; however, due to the low allele frequency in the Japanese population, the MUC5B variant alone cannot account for the high prevalence of AAV-ILD in Japan. In this study, we examined whether other IPF susceptibility alleles in TERT and DSP genes are associated with susceptibility to AAV subsets and AAV-ILD. METHODS: Five hundred and forty-four Japanese patients with AAV and 5558 controls were analyzed. Among the AAV patients, 432 were positive for myeloperoxidase (MPO)-ANCA (MPO-AAV). A total of 176 MPO-AAV patients were positive and 216 were negative for ILD based on CT or high-resolution CT. Genotypes of TERT and DSP variants were determined by TaqMan SNP Genotyping Assay, and their association was tested by chi-square test. RESULTS: When the frequencies of the IPF risk alleles TERT rs2736100A and DSP rs2076295G were compared between AAV subsets and healthy controls, both alleles were significantly increased in microscopic polyangiitis (MPA) (TERT P = 2.3 × 10-4, Pc = 0.0023, odds ratio [OR] 1.38; DSP P = 6.9 × 10-4, Pc = 0.0069, OR 1.32) and MPO-AAV (TERT P = 1.5 × 10-4, Pc = 0.0015, OR 1.33; DSP P = 0.0011, Pc = 0.011, OR 1.26). On the other hand, no significant association was detected when the allele frequencies were compared between MPO-AAV patients with and without ILD. CONCLUSIONS: Unexpectedly, TERT and DSP IPF risk alleles were found to be associated with MPA and MPO-AAV, regardless of the presence of ILD. These findings suggest that TERT and DSP may be novel susceptibility genes to MPA/MPO-AAV and also that some susceptibility genes may be shared between IPF and MPA/MPO-AAV.

Association of mucosal-associated invariant T cells with different disease phases of polymyalgia rheumatica.

OBJECTIVES: Although T cells are thought to be involved in the pathogenesis of PMR, whether innate-like T cells are involved in the process remains unknown. METHODS: The serum levels of 27 cytokines/chemokines in patients with PMR were measured by a multiplex immunoassay (Bio-Plex Assay). The cytokine-producing capacity of T and innate-like T cells was assessed by intracellular cytokine staining and flow cytometry. The frequency and activated status of T and innate-like T cells were investigated by flow cytometry and their associations with clinical parameters were assessed. RESULTS: The levels of inflammatory cytokines were associated with disease activity in PMR. The cytokine-producing capacity by CD8+ T and innate-like T cells was associated with disease activity. The frequency of HLA-DR+ CD38+ cells among CD8+ T cells was increased in patients with active disease. The frequencies of HLA-DR+ CD38+ cells among CD4+ T, mucosal-associated invariant T (MAIT) and γδ T cells were higher in patients with inactive disease. The frequency of HLA-DR+ CD38+ MAIT cells was associated with the PMR activity score and CRP levels in patients in remission. CONCLUSION: The inflammatory cytokine-producing capacity and expression of activation markers of CD8+ T and innate-like T cells were associated with the disease activity of PMR. MAIT cell activation in patients in remission may contribute to the subclinical activity of the disease.

Relationship between characteristics of spinopelvic alignment and quality of life in Japanese patients with ankylosing spondylitis: a cross-sectional study.

BACKGROUND: Studies on characteristic spinal deformities in Japanese patients with ankylosing spondylitis (AS) and data demonstrating a relationship between health-related quality of life (HRQOL) and spinopelvic alignment in these patients are lacking. METHODS: In this cross-sectional study, 50 patients with AS and without a surgical history, vertebral body fracture, or scoliosis as well as 30 control patients with degenerative lumbar kyphoscoliosis (DLKS) were included. Data collected included patient sex, age, spinopelvic parameters on sagittal full-spine standing radiographs, and HRQOL questionnaire responses. Student's t-test was used to compare the characteristics of spinopelvic parameters between the groups. A multiple regression analysis was performed to analyze correlations between spinopelvic parameters and HRQOL in the AS group. RESULTS: Global kyphosis (GK; T1-12 angle) was significantly greater in the AS group than in the DLKS group (P < 0.001), whereas the pelvic tilt (PT; posterior PT angle) was smaller in the AS group (P = 0.006). Radiographic parameters correlated with HRQOL in the AS group. Multiple regression analysis identified the sagittal vertical axis (SVA) and sacral slope (SS) as factors influencing the SRS-22 total score and SVA and GK as factors influencing Japanese Orthopaedic Association Back Pain Evaluation Questionnaire mental health (subdomain). CONCLUSIONS: Patients with AS did not use lumbar lordosis or posterior PT to compensate for their large thoracic kyphosis due to spinopelvic ankylosis. These patients showed a unique compensation pattern. The correlation/regression analysis revealed a correlation between radiographic parameters and HRQOL in patients with AS, with particular importance of SVA, SS, and GK for clinical results in AS.