LAUSR

Background Clinical features of axial involvement in psoriatic arthritis (PsA) had been studied before only at advanced stages. Skin lesion severity, HLA-B27 status and gender-specific differences in early PsA patients with axial involvement hadn’t been sufficiently studied. Objectives To compare clinical features of two early peripheral PsA patient populations – with and without axial involvement. Methods 95 patients (pts) (M/F–47/48) with early PsA according to CASPAR criteria were included; all pts had peripheral arthritis for ≤2 years; no inflammatory back pain (IBP) pts were specially selected. Mean age 36.5±10.7 years, disease duration 12.2±10.3 mo, disease activity indexes DAS=4.0±1.4, DAS28=4.2±1.1, BASDAI=4.5±1.6 (in pts with axial involvement); patient’s global disease activity (PGA) VAS 56.9±17.1. All pts were evaluated for the presence of inflammatory back pain (IBP) by ASAS criteria. The examination included X-ray of sacroiliac joints (SIJs) (pelvic radiographs), HLA B27 antigen status; magnetic resonance imaging (MRI) of SIJs was performed in 79 pts, regardless of the presence of IBP, on Signa Ovation 0,35T. Bone marrow oedema on MRI (STIR) was considered as active MRI sacroiliitis (MRI-SI). Radiographic sacroiliitis (R-SI) was considered according to New York criteria (unilateral grade ≥3 or bilateral grade ≥2). X-ray and MRI results were evaluated by an independent reader. IBP was observed in 63 cases (66.3%), MRI-SI in 28 of 79 (35.4%) examined cases, R-SI in 29 cases (30.5%). Pts were split into two groups (gr.): those with axial involvement (axPsA), that is with IBP and/or R-SI and/or MRI-SI; and those without axial involvement (having only peripheral PsA [pPsA]). The axPsA gr. included 65 (68.4%) cases, the pPsA gr. – 30 (31.6%) cases. Skin lesion severity was evaluated in terms of body surface area (BSA) affected and Psoriasis Area Severity Index (PASI). When BSA was ≥3%, PASI was calculated. PASI≥11 indicates moderate and severe psoriasis. Results The following significant differences were revealed between gr. axPsA and gr. pPsA: gender-related ones: in gr. axPsA men-to-women ratio was 60.0% to 40.0%, while in gr. pPsA it was 26.7% to 73.3% (p=0.003); age-related ones: mean age of. gr. axPsA was 33.9±9.6 years, while of gr. pPsA it was 41.7±10.6 years (p=0.0007); in disease duration: in gr. axPsA it was 10.3±8.7 mo. which was less than gr. pPsA 16.1±11.7 mo. (p=0.008); in HLA-B27 antigen status: in gr. axPsA it was positive in 47.6% of pts. while in gr. pPsA in 23.3% of pts. (p=0.02); in PGA: 58.4±17.3 mm in gr. axPsA, and 49.8±16.7 mm in gr. pPsA (p=0.02); in skin lesions’ severity: it was higher in gr. axPsA: BSA median was 3.0 [1.0–9.0] in gr. axPsA and 1.0 [0.2–3.0] in gr. pPsA (p=0.007), and PASI median was 15.6 [6.6–55.2] in gr. axPsA and 6.0 [0.0–7.2] in gr. pPsA (p=0.006). Conclusions Axial involvement in early PsA patients is significantly more frequent in males and in pts with positive HLA-B27 antigen status. Axial involvement is associated with high patient-reported disease activity and severe skin lesion. These findings may have a positive impact on diagnosis of axial disease, as well as on the selection of the best therapeutic strategy. Disclosure of Interest None declared