Background Spondyloarthritis (SpA) is a group of disorders that are characterized by inflammatory involvement of the enthesis and the adjacent bone. The importance of enthesis has increased over the last years as a result of their inclusion in the recent developed Assessment of SpondyloArthritis International Society (ASAS) new classification criteria for axial and peripheral SpA. Ultrasound is superior to clinical examination for detecting early signs of enthesitis and enthesopathy and improve the knowledge about enthesis pathology. The positivity of HLA B27 has a strong association with ankylosing spondylitis and male sex is associated with X-Rays progression, but today there is few information about presence and progression of entheseal lesions in SpA.

Objectives To evaluate the influence of HLA B27 and gender on ultrasound enthuses affectation and progression in early spondyloarthritis.

Methods Longitudinal, prospective, blinded ultrasound study in patients diagnosed with early spondyloarthritis that fulfilled ASAS classification criteria. All patients underwent ultrasound MASEI index at baseline, at 6 and 12 months. Inter-reader ICC was 0,83.

Results One hundred and forty-six early SpA patients (68 females and 78 males) were examined. HLA B27 positive was present in 32% of the male patients and 16.51% of the female patients. The diagnostics, according to the order of frequency were: non-radiological spondyloarthritis (65.83%), psoriatic arthritis (17%), ankylosing spondylitis (8.33%), spondyloarthritis associated with intestinal inflammatory disease (4.17%) and reactive arthritis (4.17%). The mean ASDAS value during the first visit was 2.39 (high activity). Baseline mean visual analogic scale for pain and patient global disease assessment were 5.15±2.5 and 2.98±1.56, respectively. The mean BASFI was 2.37±2.1. The baseline mean (range) BASDAI, ASDAS, ESR and CRP measurements were 4.60±2.07, 2.41±1.17, 15.0±16.99 mm/h and 8.67±16.98 mg/l, respectively. As shown in the table, the male patients scored higher in the MASEI index during the first visit and at the 12-month visit, reaching statistical significance in both global indices and in almost all elemental lesions explored. When we analyse HLA B27 positive patients, the only significance in the MASEI index was found at the 12-month visit, and at the basal visit and the 12-month visit for thickness. After analyzing the data we estimates that the highest score in this ultrasound index was mainly influenced by the male and the positivity of HLA B27 was probably due to the greater frequency of males in this group (66.04%).

Conclusions Male gender determines a higher enthesis involvement in early spondyloarthritis while the HLA B27 seems to have a less pathogenic fact.

Disclosure of Interest : None declared

DOI 10.1136/annrheumdis-2014-eular.4444