Impact of comorbidities and extra-musculoskeletal manifestations on radiographic progression in ankylosing spondylitis

OBJECTIVE: To examine whether baseline comorbidity burden and extra-musculoskeletal manifestations (EMMs) - psoriasis, uveitis, IBD-are associated with spinal radiographic progression in ankylosing spondylitis (AS). METHODS: We analysed participants fulfilling modified New York criteria with ≥1 lateral cervical or lumbar radiograph. Radiographic progression was quantified using the modified Stoke AS Severity Score (mSASSS), excluding score 1 at each vertebral corner (range 0-48). Comorbidity count (22 self-reported conditions: 0,1,2,≥3) and ever-presence of each EMM at baseline were exposures. mSASSS change over time with exposure-time interactions was modelled using GEE; coefficients were rescaled to represent mean difference in progression (units/10 years). Models adjusted for baseline mSASSS, sex, symptom duration, CRP, HLA-B27, smoking, TNF inhibitor use, and number of EMMs or comorbidity count. Secondary analyses examined potential sex- and segment-specific effects. RESULTS: Among 1,150 individuals (mean age 44 years; 75% male; 84% HLA-B27 positive), 3,441 patient-years were analysed (median follow-up 2 years; median 2 radiographs). Compared with those with no comorbidities, progression was greater amongst patients with 2 (2.7 units/10 years; 95%CI 1.9-3.5) and ≥3 (2.3; 1.5-3.1) comorbidities. Uveitis (2.2 units/10 years; 1.3-3.0) and psoriasis (2.4 units/10 years; 1.4-3.5), but not IBD, were associated with greater progression. Sex-specific analyses suggested greater spinal progression in females than males with psoriasis. Cervical-predominant changes were seen with uveitis and psoriasis. CONCLUSION: Comorbidity burden, uveitis, and psoriasis are independently associated with greater spinal radiographic progression in AS. These readily identifiable features may inform risk stratification and targeted management strategies.