Advances in the understanding of entheseal inflammation

Abstract

The importance of enthesitis in the pathogenesis of spondyloarthropathy (SpA) is now well recognized. Several entheses comprise more than simply the insertion site, and they are part of a complex biomechanical organ to resist shear and compression. It is also evident that tendons that wrap around bony pulleys form an integral part of joint capsules, and share, along with imaging abnormalities and histopathologic changes, common anatomic, histologic, and biomechanical features with classically defined entheses. Researchers have called these regions of tendons functional entheses. Furthermore, certain synovial joints have much in common with classic entheses--most notably those lined with fibrocartilage rather than hyaline cartilage. These observations provide a unifying anatomic basis for SpA. Enthesitis is associated with underlying osteitis, whether mechanically induced or inflammatory-related--with the extent of osteitis determined by the human leukocyte antigen-B27 gene. Until recently, there was no effective therapy for resistant enthesitis, but it is now evident that enthesitis responds well to biologic blockade with anti-tumor necrosis factor. Unraveling the pathogenic basis of enthesitis will have important implications for understanding and defining therapies in SpA.

Baseline and 1-year magnetic resonance imaging of the sacroiliac joint and lumbar spine in very early inflammatory back pain. Relationship between symptoms, HLA-B27 and disease extent and persistence

“…We have previously shown that HLA-B27 determines the severity of osteitis adjacent to the plantar fascia in early SpA 20 29. This study confirms these observations at the SIJ and is in accordance with other reports also in early disease 30.…”

Differential diagnosis between rheumatoid arthritis and psoriatic arthritis: the value of ultrasound findings at metacarpophalangeal joints level

“…Some MRI studies have demonstrated a clear link between enthesitis and synovitis in individual swollen joints in PsA, but not in RA 5 12. Following this line, McGonagle et al developed the concept of the ‘enthesis organ’,13 which comprises the enthesis and also adjacent fibrocartilages and synovial membranes. Although enthesitis is typically viewed as a focal insertional disorder, MRI and US findings have demonstrated the presence of more diffuse inflammatory changes involving areas distant from the insertion sites 14 15.…”

When is arthritis reactive?

“…Enthesitis may be associated with adjacent osteitis detectable by magnetic resonance imaging. 41 Skin and nail involvement Keratoderma blenorrhagica affects 5%-10% of patients and is highly characteristic of reactive arthritis. Histologically, appearances are identical to pustular psoriasis.…”