Axial psoriatic arthritis: An update for dermatologists
Authors: Alice B. Gottlieb, Joseph F. Merola
Journal: Journal of the American Academy of Dermatology (2020)

Psoriasis is a chronic, immune-mediated, systemic, inflammatory disorder characterized by skin plaques and, often, nail disease and arthritis that contribute to reduced quality of life. Psoriatic arthritis—a heterogeneous, inflammatory, musculoskeletal disease that can cause permanent damage to both peripheral and axial joints—is the most common comorbidity of psoriasis. Axial disease occurs in 25% to 70% of patients with PsA, with some patients exclusively experiencing axial joint involvement. Early therapeutic intervention is important for preventing permanent joint and spine damage and loss of functionality in these patients. Because skin symptoms associated with psoriasis often precede psoriatic arthritis, dermatologists are uniquely positioned to play an important role in identifying and treating patients with psoriatic arthritis. Proactive screening of patients with all severities of psoriasis for the signs and symptoms of psoriatic arthritis is key to early diagnosis and intervention. In this review, we discuss the clinical presentation, risk factors, and treatment options for psoriatic arthritis with axial involvement, with the aim of helping dermatologists understand the disease and identify patients who might benefit from further assessment, treatment, and/or referral to a rheumatology practice. Psoriasis is a chronic, immune-mediated, systemic, inflammatory disorder characterized by skin plaques and, often, nail disease and arthritis that contribute to reduced quality of life. Psoriatic arthritis—a heterogeneous, inflammatory, musculoskeletal disease that can cause permanent damage to both peripheral and axial joints—is the most common comorbidity of psoriasis. Axial disease occurs in 25% to 70% of patients with PsA, with some patients exclusively experiencing axial joint involvement. Early therapeutic intervention is important for preventing permanent joint and spine damage and loss of functionality in these patients. Because skin symptoms associated with psoriasis often precede psoriatic arthritis, dermatologists are uniquely positioned to play an important role in identifying and treating patients with psoriatic arthritis. Proactive screening of patients with all severities of psoriasis for the signs and symptoms of psoriatic arthritis is key to early diagnosis and intervention. In this review, we discuss the clinical presentation, risk factors, and treatment options for psoriatic arthritis with axial involvement, with the aim of helping dermatologists understand the disease and identify patients who might benefit from further assessment, treatment, and/or referral to a rheumatology practice. Capsule Summary•Psoriasis is an inflammatory immune disease associated with psoriatic arthritis, a disease that can involve peripheral and axial joints and cause permanent joint damage and loss of function if untreated.•Dermatologists play an important role in the early diagnosis and treatment of psoriatic arthritis by proactively screening patients with psoriasis. •Psoriasis is an inflammatory immune disease associated with psoriatic arthritis, a disease that can involve peripheral and axial joints and cause permanent joint damage and loss of function if untreated.•Dermatologists play an important role in the early diagnosis and treatment of psoriatic arthritis by proactively screening patients with psoriasis. Psoriasis is a chronic, inflammatory, immune-mediated skin disorder associated with significant morbidity, reduced quality of life (QOL), and mortality1Helmick C.G. Lee-Han H. Hirsch S.C. Baird T.L. Bartlett C.L. 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Psoriasis prevalence among adults in the United States.J Am Acad Dermatol. 2014; 70: 512-516Abstract Full Text Full Text PDF PubMed Scopus (480) Google Scholar Comorbidities are common in patients with psoriasis, and psoriatic arthritis (PsA) is one of the most frequently observed.4Elmets C.A. Leonardi C.L. Davis D.M.R. et al.Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with awareness and attention to comorbidities.J Am Acad Dermatol. 2019; 80: 1073-1113Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar Approximately 25% to 30% of patients with psoriasis develop PsA,5Alinaghi F. Calov M. Kristensen L.E. et al.Prevalence of psoriatic arthritis in patients with psoriasis: a systematic review and meta-analysis of observational and clinical studies.J Am Acad Dermatol. 2019; 80: 251-265Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar,6Mease P.J. Gladman D.D. 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A prospective, clinical and radiological study of early psoriatic arthritis: an early synovitis clinic experience.Rheumatology (Oxford). 2003; 42: 1460-1468Crossref PubMed Scopus (424) Google Scholar; many patients experience irreversible joint damage and disability with disease progression.14Husted J.A. Tom B.D. Farewell V.T. Schentag C.T. Gladman D.D. A longitudinal study of the effect of disease activity and clinical damage on physical function over the course of psoriatic arthritis: does the effect change over time?.Arthritis Rheum. 2007; 56: 840-849Crossref PubMed Scopus (70) Google Scholar,15Mease P. van der Heijde D. Landewé R. et al.Secukinumab improves active psoriatic arthritis symptoms and inhibits radiographic progression: primary results from the randomised, double-blind, phase III FUTURE 5 study.Ann Rheum Dis. 2018; 77: 890-897PubMed Google Scholar Axial involvement occurs in 25% to 70% of patients with PsA,11Gottlieb A. Korman N.J. 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Korman N.J. Gordon K.B. et al.Guidelines of care for the management of psoriasis and psoriatic arthritis: section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on the biologics.J Am Acad Dermatol. 2008; 58: 851-864Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar,17Baraliakos X. Coates L.C. Braun J. The involvement of the spine in psoriatic arthritis.Clin Exp Rheumatol. 2015; 33: S31-S35PubMed Google Scholar The diagnosis is confirmed by physical examination and imaging (eg, sacroiliitis, spinal ossifications).11Gottlieb A. Korman N.J. Gordon K.B. et al.Guidelines of care for the management of psoriasis and psoriatic arthritis: section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on the biologics.J Am Acad Dermatol. 2008; 58: 851-864Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar,17Baraliakos X. Coates L.C. Braun J. The involvement of the spine in psoriatic arthritis.Clin Exp Rheumatol. 2015; 33: S31-S35PubMed Google Scholar Among patients with axial PsA, cervical spinal mobility and lateral flexion significantly decrease within 5 years if untreated.18Chandran V. Barrett J. Schentag C.T. Farewell V.T. Gladman D.D. Axial psoriatic arthritis: update on a longterm prospective study.J Rheumatol. 2009; 36: 2744-2750Crossref PubMed Scopus (69) Google Scholar Additionally, sacroiliitis worsens with time; 37% and 52% of patients develop grade 2 or higher sacroiliitis within 5 and 10 years, respectively.18Chandran V. Barrett J. Schentag C.T. Farewell V.T. Gladman D.D. Axial psoriatic arthritis: update on a longterm prospective study.J Rheumatol. 2009; 36: 2744-2750Crossref PubMed Scopus (69) Google Scholar Therefore, early identification and treatment of patients with axial PsA is critical. Cutaneous manifestations of psoriasis can precede the onset of PsA by approximately 3 to 8 years,19Tascilar K. Aydin S.Z. Akar S. et al.Delay between the onset of psoriasis and arthritis in PsA patients from the PsART international cohort [abstract].Arthritis Rheumatol. 2019; 71: 2854Google Scholar and 1% to 3% of patients with psoriasis develop PsA annually.5Alinaghi F. Calov M. Kristensen L.E. et al.Prevalence of psoriatic arthritis in patients with psoriasis: a systematic review and meta-analysis of observational and clinical studies.J Am Acad Dermatol. 2019; 80: 251-265Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar,20Christophers E. Barker J.N. Griffiths C.E. et al.The risk of psoriatic arthritis remains constant following initial diagnosis of psoriasis among patients seen in European dermatology clinics.J Eur Acad Dermatol Venereol. 2010; 24: 548-554Crossref PubMed Scopus (99) Google Scholar Therefore, dermatologists play a critical role in early detection for patients with PsA.11Gottlieb A. Korman N.J. Gordon K.B. et al.Guidelines of care for the management of psoriasis and psoriatic arthritis: section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on the biologics.J Am Acad Dermatol. 2008; 58: 851-864Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar However, PsA is frequently underdiagnosed, with up to 41% of patients with psoriasis treated at dermatology centers having undiagnosed PsA.6Mease P.J. Gladman D.D. Papp K.A. et al.Prevalence of rheumatologist-diagnosed psoriatic arthritis in patients with psoriasis in European/North American dermatology clinics.J Am Acad Dermatol. 2013; 69: 729-735Abstract Full Text Full Text PDF PubMed Scopus (255) Google Scholar,21Haroon M. Kirby B. FitzGerald O. High prevalence of psoriatic arthritis in patients with severe psoriasis with suboptimal performance of screening questionnaires.Ann Rheum Dis. 2013; 72: 736-740Crossref PubMed Scopus (187) Google Scholar To address this problem, the new American Academy of Dermatology/National Psoriasis Foundation guidelines emphasize the role of dermatologists in recognizing PsA and recommend proactive screening of patients.4Elmets C.A. Leonardi C.L. Davis D.M.R. et al.Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with awareness and attention to comorbidities.J Am Acad Dermatol. 2019; 80: 1073-1113Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar Therefore, it is important that dermatologists be familiar with the signs of PsA, including those associated with axial involvement. Here, we review axial PsA and describe its clinical presentation, risk factors, pathology, and treatment options. Axial involvement in PsA usually occurs in young patients (<40 years old).22Jadon D.R. Sengupta R. Nightingale A. et al.Axial disease in psoriatic arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis.Ann Rheum Dis. 2017; 76: 701-707Crossref PubMed Scopus (73) Google Scholar Although axial PsA had been thought to be more prevalent in men, an analysis of the US Corrona PsA/Spondyloarthritis Registry—which compared patients with PsA with and without axial involvement—found no significant differences in the proportion of men and women with axial involvement.23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar Most patients with PsA have preceding psoriasis, but a small percentage (approximately 15%) have no psoriasis at diagnosis.24Ritchlin C.T. Colbert R.A. Gladman D.D. Psoriatic arthritis.N Engl J Med. 2017; 376: 957-970Crossref PubMed Scopus (439) Google Scholar That proportion may be lower if one includes inverse/intertriginous psoriasis, which occurs in less frequently examined areas of body folds.25Merola J.F. Li T. Li W.Q. Cho E. Qureshi A.A. Prevalence of psoriasis phenotypes among men and women in the USA.Clin Exp Dermatol. 2016; 41: 486-489Crossref PubMed Scopus (30) Google Scholar Patients with PsA can also present with enthesitis, dactylitis (sausage digit), nail changes, and peripheral arthritis.11Gottlieb A. Korman N.J. Gordon K.B. et al.Guidelines of care for the management of psoriasis and psoriatic arthritis: section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on the biologics.J Am Acad Dermatol. 2008; 58: 851-864Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar,22Jadon D.R. Sengupta R. Nightingale A. et al.Axial disease in psoriatic arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis.Ann Rheum Dis. 2017; 76: 701-707Crossref PubMed Scopus (73) Google Scholar,23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar,26Perez Alamino R. Maldonado Cocco J.A. Citera G. et al.Differential features between primary ankylosing spondylitis and spondylitis associated with psoriasis and inflammatory bowel disease.J Rheumatol. 2011; 38: 1656-1660Crossref PubMed Scopus (48) Google Scholar Typical symptoms of axial PsA include morning back/neck stiffness that lasts longer than 30 minutes and neck or back pain that improves with activity and worsens after prolonged inactivity,11Gottlieb A. Korman N.J. Gordon K.B. et al.Guidelines of care for the management of psoriasis and psoriatic arthritis: section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on the biologics.J Am Acad Dermatol. 2008; 58: 851-864Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar,17Baraliakos X. Coates L.C. Braun J. The involvement of the spine in psoriatic arthritis.Clin Exp Rheumatol. 2015; 33: S31-S35PubMed Google Scholar,18Chandran V. Barrett J. Schentag C.T. Farewell V.T. Gladman D.D. Axial psoriatic arthritis: update on a longterm prospective study.J Rheumatol. 2009; 36: 2744-2750Crossref PubMed Scopus (69) Google Scholar,23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar which are defining features of inflammatory neck/back pain (Fig 1),27Rudwaleit M. Metter A. Listing J. Sieper J. Braun J. Inflammatory back pain in ankylosing spondylitis: a reassessment of the clinical history for application as classification and diagnostic criteria.Arthritis Rheum. 2006; 54: 569-578Crossref PubMed Scopus (379) Google Scholar,28Sieper J. van der Heijde D. Landewe R. et al.New criteria for inflammatory back pain in patients with chronic back pain: a real patient exercise by experts from the Assessment of SpondyloArthritis International Society (ASAS).Ann Rheum Dis. 2009; 68: 784-788Crossref PubMed Scopus (359) Google Scholar as well as limited mobility.17Baraliakos X. Coates L.C. Braun J. The involvement of the spine in psoriatic arthritis.Clin Exp Rheumatol. 2015; 33: S31-S35PubMed Google Scholar However, 20% of patients show no symptoms of axial involvement18Chandran V. Barrett J. Schentag C.T. Farewell V.T. Gladman D.D. Axial psoriatic arthritis: update on a longterm prospective study.J Rheumatol. 2009; 36: 2744-2750Crossref PubMed Scopus (69) Google Scholar,29Queiro R. Belzunegui J. Gonzalez C. et al.Clinically asymptomatic axial disease in psoriatic spondyloarthropathy. A retrospective study.Clin Rheumatol. 2002; 21: 10-13Crossref PubMed Scopus (58) Google Scholar; these patients are usually diagnosed with PsA because they present with other PsA-related symptoms, such as dactylitis or arthritis.29Queiro R. Belzunegui J. Gonzalez C. et al.Clinically asymptomatic axial disease in psoriatic spondyloarthropathy. A retrospective study.Clin Rheumatol. 2002; 21: 10-13Crossref PubMed Scopus (58) Google Scholar,30Cohen J.M. Husni M.E. Qureshi A.A. Merola J.F. Psoriatic arthritis: it's as easy as "PSA".J Am Acad Dermatol. 2015; 72: 905-906Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar Sacroiliitis is a common feature of axial PsA (25%-50% of patients)31Gladman D.D. Clinical, radiological, and functional assessment in psoriatic arthritis: is it different from other inflammatory joint diseases?.Ann Rheum Dis. 2006; 65: iii22-iii24PubMed Google Scholar, 32Haroon M. Winchester R. Giles J.T. Heffernan E. FitzGerald O. Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis.Clin Exp Rheumatol. 2017; 35: 270-276PubMed Google Scholar, 33Williamson L. Dockerty J.L. Dalbeth N. McNally E. Ostlere S. Wordsworth B.P. Clinical assessment of sacroiliitis and HLA-B27 are poor predictors of sacroiliitis diagnosed by magnetic resonance imaging in psoriatic arthritis.Rheumatology (Oxford). 2004; 43: 85-88Crossref PubMed Scopus (93) Google Scholar and is frequently asymmetric (73% of patients).32Haroon M. Winchester R. Giles J.T. Heffernan E. FitzGerald O. Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis.Clin Exp Rheumatol. 2017; 35: 270-276PubMed Google Scholar Patients may present with alternating pain over the sacroiliac joint/buttock, with the pain typically lasting longer than 20 minutes and being worse during the second half of the night (Fig 1).27Rudwaleit M. Metter A. Listing J. Sieper J. Braun J. Inflammatory back pain in ankylosing spondylitis: a reassessment of the clinical history for application as classification and diagnostic criteria.Arthritis Rheum. 2006; 54: 569-578Crossref PubMed Scopus (379) Google Scholar,33Williamson L. Dockerty J.L. Dalbeth N. McNally E. Ostlere S. Wordsworth B.P. Clinical assessment of sacroiliitis and HLA-B27 are poor predictors of sacroiliitis diagnosed by magnetic resonance imaging in psoriatic arthritis.Rheumatology (Oxford). 2004; 43: 85-88Crossref PubMed Scopus (93) Google Scholar,34van den Berg R. de Hooge M. Rudwaleit M. et al.ASAS modification of the Berlin algorithm for diagnosing axial spondyloarthritis: results from the Spondyloarthritis Caught Early (SPACE)-cohort and from the Assessment of Spondyloarthritis international Society (ASAS)-cohort.Ann Rheum Dis. 2013; 72: 1646-1653Crossref PubMed Scopus (91) Google Scholar Sacroiliitis can be assessed clinically by asking simple questions (eg, "Is your pain worse at night?" or "How long does your pain typically last?") to determine if a patient's symptoms are characteristic of inflammatory sacroiliac joint pain (Fig 1). Comorbidities are common, with psoriasis being the most frequent (80% of patients).9Coates L.C. Helliwell P.S. Psoriatic arthritis: state of the art review.Clin Med (Lond). 2017; 17: 65-70Crossref PubMed Scopus (72) Google Scholar Other comorbidities of axial PsA include uveitis and inflammatory bowel disease (IBD). Uveitis occurs in 6% to 7% of patients with PsA but is more common (up to 33%) in those with axial involvement.35Paiva E.S. Macaluso D.C. Edwards A. Rosenbaum J.T. Characterisation of uveitis in patients with psoriatic arthritis.Ann Rheum Dis. 2000; 59: 67-70Crossref PubMed Scopus (109) Google Scholar Uveitis in axial PsA is more common in men, in younger patients (aged <34 years), and in those positive for human leukocyte antigen (HLA)-B27.35Paiva E.S. Macaluso D.C. Edwards A. Rosenbaum J.T. Characterisation of uveitis in patients with psoriatic arthritis.Ann Rheum Dis. 2000; 59: 67-70Crossref PubMed Scopus (109) Google Scholar IBD occurs in 11% of patients with axial PsA and is significantly more common in patients with axial involvement than in those with peripheral-only PsA (2%).22Jadon D.R. Sengupta R. Nightingale A. et al.Axial disease in psoriatic arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis.Ann Rheum Dis. 2017; 76: 701-707Crossref PubMed Scopus (73) Google Scholar Axial PsA has a significant impact on QOL and is associated with worse disease than that seen in patients without axial involvement.23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar In an analysis of the US Corrona Registry, patients with axial involvement had more severe skin manifestations, higher tender joint counts, more enthesitis, and worse disease activity.23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar Similarly, patients with axial PsA had worse pain than patients without axial involvement and had significantly impaired physical function and QOL (P < .001).23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar Patients with axial involvement also had decreased work productivity, with significantly higher proportions of missed work time (10.0% vs 3.3%), overall work impairment (32.3% vs 16.8%) and overall activity impairment (37.0% vs 18.1%; P < .001 for all). Problems with walking and self-care and feelings of anxiety and depression were also common.23Mease P.J. Palmer J.B. Liu M. et al.Influence of axial involvement on clinical characteristics of psoriatic arthritis: analysis from the Corrona Psoriatic Arthritis/Spondyloarthritis Registry.J Rheumatol. 2018; 45: 1389-1396Crossref PubMed Scopus (42) Google Scholar Clinical factors associated with axial PsA include more-severe skin psoriasis, a young age at PsA onset, and severe peripheral arthritis. In 1 study, severe skin psoriasis (P = .041) and younger age at PsA onset (P < .001) correlated with developing sacroiliitis.32Haroon M. Winchester R. Giles J.T. Heffernan E. FitzGerald O. Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis.Clin Exp Rheumatol. 2017; 35: 270-276PubMed Google Scholar Additionally, peripheral joint erosions were more common in patients with asymmetric sacroiliitis, suggesting a possible association between peripheral arthritis and axial involvement in patients with PsA.32Haroon M. Winchester R. Giles J.T. Heffernan E. FitzGerald O. Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis.Clin Exp Rheumatol. 2017; 35: 270-276PubMed Google Scholar This association was further suggested by another study in which radiographic damage to peripheral joints increased the risk of developing axial PsA.36Chandran V. Tolusso D.C. Cook R.J. Gladman D.D. Risk factors for axial inflammatory arthritis in patients with psoriatic arthritis.J Rheumatol. 2010; 37: 809-815Crossref PubMed Scopus (56) Google Scholar IBD, a known comorbidity of psoriasis,4Elmets C.A. Leonardi C.L. Davis D.M.R. et al.Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with awareness and attention to comorbidities.J Am Acad Dermatol. 2019; 80: 1073-1113Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar is also a risk factor for PsA and other SpAs, with both being more common in patients with Crohn's disease.37Fragoulis G.E. Liava C. Daoussis D. Akriviadis E. Garyfallos A. Dimitroulas T. Inflammatory bowel diseases and spondyloarthropathies: from pathogenesis to treatment.World J Gastroenterol. 2019; 25: 2162-2176Crossref PubMed Scopus (45) Google Scholar,38Halling M.L. Kjeldsen J. Knudsen T. Nielsen J. Hansen L.K. Patients with inflammatory bowel disease have increased risk of autoimmune and inflammatory diseases.World J Gastroenterol. 2017; 23: 6137-6146Crossref PubMed Scopus (71) Google Scholar Sacroiliitis is estimated to occur in 12% to 46% of patients with IBD,37Fragoulis G.E. Liava C. Daoussis D. Akriviadis E. Garyfallos A. Dimitroulas T. Inflammatory bowel diseases and spondyloarthropathies: from pathogenesis to treatment.World J Gastroenterol. 2019; 25: 2162-2176Crossref PubMed Scopus (45) Google Scholar and clinically silent macroscopic and microscopic colitis occur in approximately 60% of patients with axial SpA (axSpA),37Fragoulis G.E. Liava C. Daoussis D. Akriviadis E. Garyfallos A. Dimitroulas T. Inflammatory bowel diseases and spondyloarthropathies: from pathogenesis to treatment.World J Gastroenterol. 2019; 25: 2162-2176Crossref PubMed Scopus (45) Google Scholar emphasizing the gut-axial axis. Uveitis has been identified as a risk factor for PsA, but its role as a risk factor for axial involvement remains unclear.39Eder L. Haddad A. Rosen C.F. et al.The incidence and risk factors for psoriatic arthritis in patients with psoriasis: a prospective cohort study.Arthritis Rheumatol. 2016; 68: 915-923Crossref PubMed Scopus (102) Google Scholar A notable risk factor for axial PsA is the presence of HLA-B27.36Chandran V. Tolusso D.C. Cook R.J. Gladman D.D. Risk factors for axial inflammatory arthritis in patients with psoriatic arthritis.J Rheumatol. 2010; 37: 809-815Crossref PubMed Scopus (56) Google Scholar,40Brewerton D.A. Caffrey M. Nicholls A. Walters D. James D.C. HL-A 27 and arthropathies associated with ulcerative colitis and psoriasis.Lancet. 1974; 1: 956-958Abstract PubMed Scopus (105) Google Scholar HLA-B27 is a known key genetic marker of ankylosing spondylitis (AS), is present in more than 80% of patients with AS, and is the only known genetic marker common to AS and axial PsA.41Feld J. Chandran V. Haroon N. Inman R. Gladman D. Axial disease in psoriatic arthritis and ankylosing spondylitis: a critical comparison.Nat Rev Rheumatol. 2018; 14: 363-371Crossref PubMed Scopus (58) Google Scholar Although its prevalence is lower in patients with PsA (20%),41Feld J. Chandran V. Haroon N. Inman R. Gladman D. Axial disease in psoriatic arthritis and ankylosing spondylitis: a critical comparison.Nat Rev Rheumatol. 2018; 14: 363-371Crossr