Ankylosing spondylitis and axial psoriatic arthritis are stupidly confused?

*Only for medical professionals to read and refer to the problem that has been troubled, finally understand! From August 28 to 31, 2021, the 2021 Asia-Pacific Rheumatism Alliance (APLAR) Annual Meeting was held in Kyoto, Japan.
Professor Lai-Shan Tam from the University of Hong Kong, China, brought us "Axial psoriatic arthritis-is it different from axial Spondyloarthritis?" related topics
.

 The lecture is divided into the following four parts: 1.
What is axial psoriatic arthritis (axPsA)? 2.
What is the difference between axPsA and axial spondyloarthritis (axSpA)? 3.
How to treat axPsA? 4.
Summary What is axPsA? At the 2020 GRAPPA (Psoriasis and Psoriatic Arthritis) annual meeting, the MRI working group of the GRAPPA group summarized the current status of the MRI scoring system for psoriatic arthritis (PsA) and reviewed the cases of representative patients
.

Case 1 A 50-year-old female with a 20-year history of inflammatory low back pain (IBP) did not respond to treatment with non-steroidal anti-inflammatory drugs (NSAID)
.

People with disabilities, walking on crutches
.

There was a psoriasis rash on the sole of the left foot, manifested as thoracolumbar movement pain, HLA-B27 was positive, CRP 25 mg/L, pelvic X-ray film: normal
.

X-rays of the spine suggest degenerative disc disease
.

MRI tips: MRI SLJ: no abnormalities; MRI spine: massive MRI vertebral angle inflammation and endplate inflammation; T1-weighted sequence: massive vertebral angle and endplate fat lesions, no endplate irregularities and loss of intervertebral disc height are characteristic manifestations
.

Case: A 259-year-old female suffered from pain between the shoulder blades for 3 months
.

The psoriasis rash is distributed on the elbows and knees
.

CRP 11.
2 mg/L, HLA-B27 negative, and normal pelvic and spinal X-rays
.

MRI of the pelvis: normal
.

Thoracic MRI: Inflammation is mainly concentrated in the thoracic spine
.

From a definition point of view, the diagnosis of axPsA also adopts the New York criteria for ankylosing spondylitis (AS): sacroiliac arthritis meets unilateral grade 2 or higher sacroiliac joint disease, or bilateral sacroiliac joints with grade 1 or higher radiographic changes Or IBP appears
.

At present, the diagnosis of axPsA also follows the ASAS SpA classification standard
.

However, there are still many controversies about the definition of axPsA
.

axPsA and psoriasis (PsO) constitute a unique clinical category
.

In terms of imaging, axSpA is manifested as sacroiliitis, and 35% of axPsA is manifested as solitary spondylitis without sacroiliitis
.

In terms of clinical manifestations: only 23%-43% of axPsA patients are HLA-B27 positive
.

The ASAS classification standard is that SpA patients have chronic IBP before the age of 45, but this may not be the case in a considerable number of PsA patients
.

▌ The prevalence of axPsA 1303 patients with PsA in Toronto, Canada underwent radiological evaluation.
According to the radiology mNY standard, 477 (36.
6%) patients were axPsA; Victoria et al.
studied the prevalence of sacroiliitis in PsA patients.
A total of 107 patients with PsA were enrolled.
According to the results of pelvic X-ray and MRI, only 57.
1% of patients were positive for sacroiliitis, and 27.
3% of patients with non-radiation sacroiliitis reported a history of IBP
.

▌ Calin criterion is the most consistent in judging IBP.
In order to determine the consistency between the IBP judged by rheumatologists in PsA patients and the criteria for defining IBP, and the predictive value of IBP in identifying the central axis of PsA, a standard for PsA IBP A prospective study of the prevalence, characteristics, and clinical manifestations of the disease used the kappa coefficient to investigate the consistency between rheumatologists’ judgments of IBP and IBP criteria (assessed by Calin, Rudwaleit, and the International Spondyl Arthritis Association)
.

The study included 171 patients (52% were men, with an average age of 46.
6 years old who were diagnosed with PsA)
.

Ninety-six patients (56.
13%) had chronic back pain (CBP), 65 (38.
01%) patients had IBP, and 54 (32%) patients had evidence of spinal radioactivity changes
.

The consistency between the judgment of IBP and the IBP Calin standard was the highest (0.
70)
.

In the Rudwaleit criteria, the positive likelihood ratio for the presence of radiation axis involvement was the highest (2.
17)
.

Except for patients with back pain who have a higher BASIDS index and a lower HLA-B38 carrier rate, there was no difference between axPsA patients with or without back pain
.

▌ AS diagnostic criteria are not suitable for axPsA in the face of PsA axis involvement, and it may not be appropriate to use AS diagnostic criteria
.

Only a small part of axPsA patients have IBP, and less than one-third of patients have evidence of spinal radioactivity changes.
IBP/X-ray or MRI assessment of sacroiliac joint changes may not be the "gold standard" for axPsA axis involvement
.

The criteria we set for AS may not be able to identify the axial lesions in PsA patients well
.

PsA patients need more targeted imaging examinations to determine axial disease
.

▌ Traditional IBP criteria have low sensitivity in diagnosing PsA patients.
In order to study the sensitivity of traditional IBP criteria in diagnosing PsA patients, 406 PsA patients were enrolled in the study.
A total of 27% (109/406) were diagnosed as axPsA by specialists
.

All patients with axPsA have radiation sacroiliitis, and have a history or past history of CBP
.

The average age of axPsA patients was 51 ± 10 years, and 53% were male
.

In patients diagnosed with axPsA, we found that regardless of the presence or absence of CBP, regardless of the characteristics of back pain, its sensitivity and specificity were very low (68% and 60%, respectively)
.

Interestingly, in the diagnosed axPsA, the sensitivity of the IBP criteria is poor, but the specificity is quite good (sensitivity and specificity are 59% and 84%, respectively)
.

In addition, the study also reviewed the performance of CBP and IBP in patients with active axPsA
.

CBP has 100% sensitivity, but only 66% specificity; however, the accuracy of meeting the IBP criteria to predict active axPsA is significantly improved (sensitivity and specificity are 82% and 88%, respectively)
.

Figure 1: The sensitivity and specificity of CBP and IBP in diagnosing axPsA.
What are the differences between axPsA and axSpA? ▌ The prevalence, clinical and imaging differences between axPsA and AS A prospective single-center, cross-sectional, observational study comparing the prevalence, clinical and imaging differences between axPsA and AS in SpA
.

A total of 402 cases of PsA and AS were recruited (according to a 1:1 ratio)
.

According to their radiological axial lesions and history of psoriasis, they were re-divided into three groups: 118 cases of axPsA, 127 cases of PsA (pPsA) with only peripheral involvement, and 157 cases of AS patients (without psoriasis)
.

25.
42% (30/118) of axPsA patients showed asymptomatic axial lesions
.

Of the PsA cases, only 23.
88% (48/201) met the modified AS New York standard, and only 24.
38% (49/201) met the PsA classification standard
.

7.
09% (9/127) of pPsA, 39.
83% (47/118) of axPsA and 89.
17% (140/157) of AS patients were positive for HLA-B*27 alleles (mainly HLA-B*27)
.

Compared with axPsA cases, the positive rate of HLA-B*27 in AS is higher, and the positive rate in pPsA is lower
.

The disease activity and disability of axPsA and AS are comparable
.

A considerable number of patients with axPsA have spondylitis, but do not have sacroiliitis (39/118; 33.
05%)
.

Compared with axPsA, complete ankylosis of the sacroiliac joint and bone bridge formation are more common in AS
.

The axial imaging lesions of AS patients are more serious than axPsA
.

Among the 118 cases of axPsA, 45/118 (38.
14%) had sacroiliac arthritis with spondylitis, 39/118 (33.
05%) had only spondylitis without sacroiliitis, and 34/118 (28.
81%) had sacroiliac Arthritis without spondylitis
.

Most axPsA patients with only spondylitis and no sacroiliitis have back pain symptoms (22/39, 56.
41%), although compared with axPsA patients with sacroiliitis, the incidence of symptoms is lower (66/ 79, 83.
54%)
.

Another similar study enrolled 766 AS patients, of which 91 had PsO and 675 had no PsO; the control group enrolled 1303 PsO patients, including 477 axPsA patients and 826 pPsA patients
.

The following table describes the baseline demographic and genetic characteristics of these groups
.

AS patients are younger at diagnosis than PsA patients
.

Compared with PsA patients, there are more men with AS, and HLA-B*27 positive is more common
.

Table 1: Baseline demographic and genetic characteristics of the four groups of patients.
The clinical characteristics of AS and PsA patients are as follows: regardless of whether they are accompanied by axial lesions, PsA patients have more obvious inflammatory activities and a higher risk of joint damage
.

Patients with AS are more prone to back pain and have a higher BASMI activity index
.

Enthesitis is most common in the pPsA group; hand and foot inflammation is only diagnosed in the PsA group.
Iritis is not common clinically, but it is more likely to occur in patients with AS
.

More AS patients began to receive biological therapy, and more PsA patients received conventional DMARD treatment
.

Table 2: Clinical characteristics of patients with AS and PsA▌ The clinical response of axSpA and axPsA patients to bDMARDs is similar.
A single-center observational study compared the clinical characteristics of patients with axSpA and axPsA and their response to bDMARDs
.

A total of 352 patients were enrolled, 287 (81.
5%) axSpA and 65 (18.
5%) axPsA patients
.

Except for HLA-B27 positivity and axSpA, peripheral performance is related to axPsA, there is no significant difference in the baseline characteristics of the two diseases
.

After 6 months and 12 months of bDMARDs treatment, the proportion of patients with axSpA and axPsA reaching ID/LDA [Note: disease inactivity (ID), low disease activity (LDA)] is comparable: 53% vs 58%
.

In axSpA and axPsA, men appear to be associated with achieving LDA
.

In general, in clinical practice, patients with axSpA and axPsA show many similarities, including clinical responses to bDMARDs
.

Males may be a better predictor of response to treatment for both diseases
.

Figure 2: Clinical response of axSpA and axPsA patients to bDMARDs▌ The thoracic spine is the most common site of spondylitis in PsA patients.
A 24-week prospective observational study studied the effect of adalimumab on the axial manifestations of PsA patients in Japan
.

This study used MRI to assess the axial involvement of patients with PsA
.

The patient was treated with adalimumab for 24 weeks
.

MRI examinations were performed during the baseline period and 24 weeks of treatment
.

This study included 37 PsA patients.
In 91% (n=31) of PsA patients, spondylitis positive was observed in at least one site
.

There were 48, 67, and 53 arthritic sites in the cervical, thoracic, and lumbar spine, respectively
.

All patients were diagnosed with sacroiliac arthritis ≥ grade 1 by MRI, and 28 patients (82%) had at least one sacroiliac area with sacroiliac arthritis grade ≥ grade 2
.

The severity of sacroiliitis on the right is higher than that on the left
.

In 34 patients with PsA, the thoracic spine is the most common site of spondylitis
.

In addition, 24 weeks of adalimumab treatment can improve the average number of spondylitis and the average grade of sacroiliitis
.

How to treat axPsA? ▌ The application of ustekinumab in patients with axPsA (initial treatment of TNFi).
The IL-12/23 inhibitor ustekinumab has achieved good results in PsA patients with peripheral arthritis.
Two Phase III studies (PSUMIT-1 and 2) analyzed the efficacy of Uselnumab on axPsA
.

In general, the clinical remission (1.
99 vs-0.
18) and mBASDAI index (2.
09 vs-0.
59) of the patients in the uzumumab treatment group after neck/back/hip pain at the 24th week were all greater than the comfort Patients in the drug treatment group
.

Compared with HLA-B27-negative patients, HLA-B27-positive patients have greater improvement in neck/back/hip joint pain and fatigue
.

Compared with the placebo group, a greater proportion of patients in the Useltuzumab group achieved clinical improvement in ASDAS at week 24
.

▌ Guselkumab can be expected to treat PsA.
Interleukin-23 (IL-23)/T-helper 17 pathway is related to the pathogenesis of PsA, and Guselkumab is an IL-23 inhibitor that specifically binds to IL-23 p19 subunit
.

A study aimed to evaluate the therapeutic effect of Guselkumab on patients with PsA
.

The patients were randomly divided into the following 3 groups (1:1:1): subcutaneous injection of Guselkumab 100 mg group every 4 weeks; 0th week, 4th week, and then every 8 weeks Guselkumab 100 mg group or placebo group
.

Studies have shown that compared with the placebo group, patients in the Guselkumab group who were administered every 4 weeks and every 8 weeks had a higher percentage of improvement in BASDAI-related endpoints at week 24, and it was effective in patients with active PsA who did not receive biologic therapy.
Of
.

It is suggested that Guselkumab has a good therapeutic effect on PsA
.

Figure 3: In week 24, compared with PBO, the improvement of Basdai-related endpoints in the GUS group is better summarized: In general, axSpA and axPsA are two different diseases, regardless of demographics, clinical manifestations, imaging, Genetics, and treatment response
.

axSpA is more common in men, and the age of onset is relatively young
.

Clinically, most patients have the characteristics of IBP, and about 15%-30% of patients are peripherally affected
.

On the image, symmetrical sacroiliac arthritis and symmetrical ligament osteophyte formation are typical manifestations, and lumbar facet joint fusion is more likely to occur
.

In terms of genes, the proportion of HLA-B27-positive patients is relatively high (90%)
.

The incidence of axPsA is similar in men and women, and the age of onset is relatively older
.

The incidence of IBP is lower than that of axSpA.
Most patients have peripheral involvement and may not have any symptoms
.

On imaging, cervical spine involvement is more common, the incidence of cervical facet joint fusion is higher, sacroiliac arthritis is not serious, and often asymmetrical, marginal osteophytes and paravertebral ossification are rare, and symmetrical osteophytes are rare
.

Genetically, only 14%-44% of patients are HLA-B27 positive, and HLA-B08 and HLA-B38 are more common
.

The IL-17 inhibitor skukuzumab, the IL-23 inhibitor gussetzumab, and the IL-12/23 inhibitor Useltuzumab are more effective in the analysis of the efficacy data of axPsA
.

Table 3: Comparison of axSpA and axPsA in various aspects.
In general, axPsA is a heterogeneous group of diseases, in which axial lesions are different from axSpA
.

In addition to genetic, clinical and imaging differences, the response of axPsA to treatment may be different from that of axSpA
.

In order to meet the needs of the research and treatment of the pathogenesis of the disease, it is imperative to determine a new classification model of axPsA through international multidisciplinary cooperation
.

Experts commented that before 2009, the concept of central axis SpA had not appeared, but the general term for SpA, which included AS and PsA
.

In 2009, ASAS proposed a new classification standard for "axial SpA", which includes "radiologically negative axSpA (nr-axial-SpA)" and "AS", which gives patients who have not reached the AS stage Patients in the early stage have a relatively clear classification diagnosis.
In the follow-up drug clinical trials, the indications are also included in the "radiological negative axSpA", which provides clinical diagnosis and treatment basis
.

In the study, the diagnosis of axPsA was defined, and the New York criteria of AS were also referenced: sacroiliac arthritis meets unilateral grade 2 or higher sacroiliac joint disease, or bilateral sacroiliac joints with grade 1 or higher radiographic changes or IBP
.

In this content, comparing the differences between PsA and AS, axSpA and axPsA, there are some differences between the two
.

Such as: (a) positive rate of sacroiliitis: PsA<AS, axPsA<axSpA; (b) positive rate of HLA-B27: PsA<AS, axPsA<axSpA; (c) IBP: PsA<AS, axPsA<axSpA
.

The study mentioned in this article also compares the differences in the clinical characteristics of patients with AS and PsA: (1) Regardless of whether they are accompanied by axial lesions, patients with PsA have more obvious inflammatory activities and a higher risk of joint damage
.

(2) AxPsA more often has enthesitis, and AS is more likely to have iritis.
The study also found that more AS patients receive biological treatment, while PsA patients receive conventional DMARD treatment
.

(3) Cervical spine involvement is more common on axPsA imaging, the incidence of cervical facet joint fusion is higher, and genetics, only 14%-44% of patients are HLA-B27 positive, and HLA-B08 and HLA-B38 are more common Positive, there is still a certain difference from axSpA
.

(4) The IL-17 inhibitor skukuzumab, the IL-23 inhibitor gussetzumab, and the IL-12/23 inhibitor Uselnumumab are more effective in the analysis of the efficacy data of axPsA
.

In the clinic, we need to realize that there are certain differences between PsA&AS, axPsA&axSpA, and in clinical diagnosis and treatment, we must make certain appropriate judgments and choose a more suitable plan for the patient
.

 Expert profile Lin Zhiming, Chief Physician, Chief Physician, Department of Rheumatology and Immunology, The Third Affiliated Hospital of Sun Yat-sen University, Vice Chairman, Chinese Medical Doctor Association, Rheumatology and Immunology Branch, Member of the Youth Committee of the Chinese Medical Association Rheumatology Branch Member of the National Clinical Research Center for Skin and Immunological Diseases, Member of the Chinese Rheumatology-Related Reproductive and Pregnancy Research Committee Member of the Professional Committee of Rheumatology and Immunology, Cross-Strait Medical and Health Exchange Association Talents Outstanding young medical talents of Guangdong Provincial Health and Family Planning Commission, Guangzhou Science and Technology Innovation Commission, "Pearl River Rising Star" Talent Reference: [1] Maksymowych et al.
J Rhuematol 2021 Feb 15;jrheum.
201676[2]Xenofon Barallakos et al.
Ann rheum Dis 2021:80:582-590[3]Ann Rheum Dis Month 2018 Vol 0 No 0[4]Yap KS,et al.
Ann Rheum Dis 2018;0:1–5.
doi:10.
1136/annrheumdis-2018-213334 [5]Jadon DR,et al.
Ann Rheum Dis 2016;0:1–7.
doi:10.
1136/annrheumdis-2016-209853RHEUMATOLOGY.
doi:10.
1093/rheumatology/kez457[6]Ther Adv Musculoskel Dis 2020,Vol.
12: 1–8 DOI:0.
1177/1759720X20971889Rheumatology 2021;00:1–10 doi:10.
1093/rheumatology/keaa829 Source of this article: Medical rheumatism channel Author: Yao Xiaoyan This article review + comment: Lin Zhiming, chief physician, Sun Yat-sen University Third Affiliated Hospital Editor: Cassette copyright statement The published content is accurate and reliable at the time of review, but it does not make any promises or guarantees on the timeliness of the published content, as well as the accuracy and completeness of the cited information (if any), and does not assume that the content has been Any liability caused by outdated, possible inaccuracy or incompleteness of the cited information
.

Relevant parties are requested to check separately when adopting or using this as a basis for decision-making
.