To determine the effect of tumor necrosis factor α (TNFα) blockade with etanercept on the clinical manifestations of resistant spondylarthropathy (SpA) and on axial and peripheral entheseal lesions using magnetic resonance imaging (MRI).

We performed a descriptive longitudinal study of 10 SpA patients, all of whom had active inflammatory back pain and peripheral involvement. Patients were treated with 25 mg subcutaneous etanercept twice weekly for 6 months. Clinical assessments included entheseal count, visual analog scale (VAS) scores for spinal pain during the day and night, VAS scores for entheseal pain, the Bath Ankylosing Spondylitis Functional Index (BASFI), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and the Ankylosing Spondylitis Quality of Life (ASQoL) questionnaire. MRI scans of sacroiliac (SI) joints, the lumbar spine, and affected peripheral joints were performed using a 1.5T scanner employing T1‐weighted, T2‐weighted fat‐suppressed (FS), and T1‐weighted FS postgadolinium sequences at baseline and at 6 months. Enthesitis and associated osteitis were scored semiquantitatively in pre‐ and posttreatment scans.

There was a statistically significant improvement in all clinical and functional parameters (P = 0.008 for VAS spinal pain score during the day and for VAS spinal pain score during the night, P = 0.008 for the BASFI, and P = 0.005 for the BASDAI) as well as in quality of life (P = 0.005 for the ASQoL) at 6 months. Nine patients had a total of 44 MRI‐detectable entheseal lesions. These were seen in the SI joints in 6 patients (n = 15 lesions), in the lumbar or cervical spine in 9 patients (n = 22 lesions), and in peripheral joints in 5 patients (n = 7 lesions). Overall, 86% of MRI‐detected entheseal lesions either regressed completely or improved. No new lesions developed.

These findings suggest that TNFα blockade with etanercept is markedly effective in controlling the clinical manifestations of SpA that is resistant to disease‐modifying antirheumatic drugs. This is associated with marked improvement of enthesitis and associated osteitis pathology as determined by MRI.