Arthropathy associated with IBD can involve both peripheral and axial joints. IBD associated arthropathy is considered a type of seronegative spondyloarthropathy (SpA). Spondyloarthropathies (which also include Ankylosing Spondylitis (AS), Psoriatic Arthritis, Reactive Arthritis, and Undifferentiated SpA), are characterized by axial and peripheral joint disease with inflammatory features and classically a negative rheumatoid factor. Spondyloarthropathies share a common genetic predisposition, including HLA-B27 association. Extraarticular manifestations such as skin manifestations, dactylitis, enthesopathy, and eye disease can also be seen. IBD-associated arthritis is more akin to AS than to the other subtypes of SpA in that it is more likely to be symmetric and continuous, whereas reactive arthritis or psoriatic arthritis can be asymmetric or have non-continuous lesions within the spine. The European Spondyloarthropathy Study Group criteria (ESSG) are most commonly used for classification of SpA [3].
Orchard et al. [4] defined two categories of IBD patients with peripheral arthritis. Type 1 is a pauci/oligo-articular arthritis with swelling and pain of five or fewer joints, particularly affecting large joints in the lower extremities. Type 1 arthritis tends to be acute and self-limiting, and correlates with IBD activity. Joint symptoms can occur prior to the diagnosis of IBD. Type 2 peripheral arthritis has a more polyarticular (affecting greater than five joints), symmetrical distribution, affecting upper limbs predominantly (MCPs commonly affected). Type 2 peripheral arthritis may be chronic and is less likely to parallel the IBD activity. In both types, peripheral arthritis tends to be non-deforming and non-erosive. The possibility of an alternative diagnosis, such as Rheumatoid Arthritis or PsA should be considered in IBD patients who develop erosive arthritis.
Axial arthropathy in IBD can involve isolated sacroiliitis (frequently asymptomatic), inflammatory back pain (IBP), and AS. As the terms AS, sacroillitis and IBP have some overlap, the distinctions can be confusion. AS required the presence of sacroiliitis on imaging in addition to either back pain and stiffness for greater than 3 months that does not improve with rest but does improve with exercise, or limitation of motion in both the sagittal and frontal planes, or limitation of chest wall expansion after correcting for age and gender. Sacroillitis is defined as inflammation of the sacroiliac joint, and can be asymptomatic or painful. Inflammatory back pain is a clinical diagnosis, and does not require imaging. The Calin criteria can be used to differentiate IBP from mechanical back pain, and are fulfilled if at least 4/5 are present: (1) age of onset <40, (2) duration >3 months, (3) insidious onset, (4) morning stiffness, and (5) improvement with exercise [5]. New IBP criteria developed by the Assessment of SpondyloArthritis International Society (ASAS) in 2009 may have better specificity than the Calin criteria [6].
).
