Spondyloarthropathies That Mimic Ankylosing Spondylitis: A Narrative Review

Abstract

Ankylosing spondylitis is the most common type of seronegative inflammatory spondyloarthropathy often presenting with low back or neck pain, stiffness, kyphosis and fractures that are initially missed on presentation; however, there are other spondyloarthropathies that may present similarly making it a challenge to establish the correct diagnosis. Here, we will highlight the similarities and unique features of the epidemiology, pathophysiology, presentation, radiographic findings, and management of seronegative inflammatory and metabolic spondyloarthropathies as they affect the axial skeleton and mimic ankylosing spondylitis. Seronegative inflammatory spondyloarthropathies such as psoriatic arthritis, reactive arthritis, noninflammatory spondyloarthropathies such as diffuse idiopathic skeletal hyperostosis, and ochronotic arthritis resulting from alkaptonuria can affect the axial skeleton and present with symptoms similar those of ankylosing spondylitis. These similarities can create a challenge for providers as they attempt to identify a patient's condition. However, there are characteristic radiographic findings and laboratory tests that may help in the differential diagnosis. Axial presentations of seronegative inflammatory, non-inflammatory, and metabolic spondyloarthropathies occur more often than previously thought. Identification of their associated symptoms and radiographic findings are imperative to effectively diagnose and properly manage patients with these diseases.

Keywords: Inflammatory; back; metabolic; neck pain; spondyloarthropathies.

Figure 1.

A 50-year-old man presented to the clinic with mid back pain that started three months ago after a fall off a ladder. CT scan midsagittal view (A) of the thoracic spine showing T10 hyperextension fracture nonunion (arrowhead). Plain radiograph anteroposterior view (B) of the lumbar spine showing bamboo spine, fusion of the sacroiliac joints (arrows). Both the CT and the plain radiograph showing preservation of the intervertebral disc space (stars). CT scan axial view (C) of the pelvis showing fusion of the sacroiliac joints (arrows).

Figure 2.

A 43-year-old man presented to the clinic with neck pain and stiffness. He denied any back pain. He had a long history of psoriasis with multiple peripheral joint pain and stiffness. Upright plain lateral radiograph (A), CT midsagittal (B) and parasagittal (C) images of the cervical spine.

Figure 3.

A 68-year-old man presented to the emergency department with severe low back pain after a fall in the shower. He had a long history of alkaptonuria and ochronosis with joint replacements of bilateral hips, knees, and the left shoulder. CT midsagittal (A) and (B) coronal images showing complete ankylosing of the facet joints, calcification of the intervertebral disc as well as anterior and posterior ligaments, with three columns unstable hyperextension injury of L3. The sacroiliac joints are not fused which differentiates ochronotic spondyloarthropathy from ankylosing spondylitis.