Differentials
Ankylosing spondylitis
SIGNS / SYMPTOMS
INVESTIGATIONS
Radiographs reveal syndesmophytes (ossification of spinal ligaments forming bony bridges between vertebrae, projecting from the annulus fibrosus) and sacroiliitis (unilateral or bilateral; joint space stenosis, subchondral sclerosis, and ankylosis of the lower one third [synovial] part of the sacroiliac joint).
The presence of radiographic sacroiliitis is a requirement for fulfilling the modified New York classification criteria for ankylosing spondylitis (AS), which is the most specific criteria set for reaching a diagnosis.[49][50]
A negative radiograph does not exclude the diagnosis.
MRI imaging of the whole spine and sacroiliac joints may demonstrate evidence of bone marrow oedema, supporting an inflammatory cause for spinal disease.
HLA-B27 is present in about 90% of patients with AS.[51]
Spondylosis
SIGNS / SYMPTOMS
Thoracic spine is not involved until late stages with spondylosis.[9] Early involvement of the thoracic spine in DISH.
Involvement of the cervical and lumbar spine usually limited to the lower portions of these segments in spondylosis, but can occur anywhere in the spine.
Pseudogout
SIGNS / SYMPTOMS
Episodic flares of painful and tender joints.
Typically self-limiting.
INVESTIGATIONS
Radiographs reveal evidence of chondrocalcinosis.
Charcot spine
SIGNS / SYMPTOMS
History of spinal cord injury, or an underlying disease that impairs pain sensation and proprioception.[53]
INVESTIGATIONS
Radiographs reveal evidence of bone destruction and resorption as well as new bone formation (i.e., vertebral destruction/erosion accompanied by osteolysis and/or osteosclerosis and hypertrophic hyperostosis).
Repetitive trauma
SIGNS / SYMPTOMS
History of trauma recurring at the same site.
History of pain over site of injury. Wound or visible signs of injury, such as ecchymoses.
INVESTIGATIONS
Radiographic changes (with evidence of osteophytes or enthesophytes) limited to the site of trauma.
Fluorosis
SIGNS / SYMPTOMS
Pain over extremities (hands/feet). Possible tooth discoloration may be noted.[54]
INVESTIGATIONS
Radiographs reveal periostitis.
Adverse effect of systemic retinoid therapy
SIGNS / SYMPTOMS
Reported history of systemic retinoid therapy.
Back and spine pain.
Disease progression may not continue after cessation of retinoid therapy.[55]
INVESTIGATIONS
Radiographs may reveal evidence of skeletal hyperostosis and ligament ossification (particularly along the anterior longitudinal ligament).
Serial radiography may not show progression of disease following discontinuation of retinoid therapy.
Peripheral osteoarthritis
SIGNS / SYMPTOMS
Commonly involved joints include the knee, hip, hands.
Family history of osteoarthritis.
Bony deformities are common in the hands.[56]
Note that osteoarthritis and DISH may co-exist in some patients.
INVESTIGATIONS
Clinical diagnosis.
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