A 42-year-old man comes to the emergency department due to severe back pain following a fall. He tripped while getting out of his car and landed on his back. The patient has a 20-year history of ankylosing spondylitis, for which he takes prescribed medication regularly, but he has never had pain similar to this. His medical history is also notable for a duodenal ulcer 7 years ago. The patient does not use alcohol, tobacco, or illicit drugs. Vital signs are normal except for a mild, regular tachycardia. He appears to be in pain, with grimacing and diaphoresis. Examination shows midline tenderness over the upper lumbar region. Spinal range of motion is restricted. There is no tenderness over the sacroiliac joints. Cardiac auscultation shows an early diastolic murmur. Which of the following is the most likely cause of his current pain?
Ankylosing spondylitis | |
Inflammatory back pain |
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Examination findings |
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Complications |
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Laboratory |
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Imaging |
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CRP = C-reactive protein; ESR = erythrocyte sedimentation rate. | |
This patient has ankylosing spondylitis (AS) with reduced range of motion in the spine. He also has a murmur suggesting aortic regurgitation, a common finding in chronic AS. He now has new acute pain following a fall. Although a ground-level fall would be unlikely to cause a fracture in an otherwise healthy man of his age, the clinical suspicion for vertebral fracture should be much higher in a patient with AS.
Patients with longstanding AS can develop osteopenia/osteoporosis due to increased osteoclast activity in the setting of chronic inflammation (mediated by TNF-α and interleukin-6). In addition, spinal rigidity in these patients can increase the risk of vertebral fracture, which often results from minimal trauma. Associated findings may include thoracic wedging and hyperkyphosis.
(Choices A and E) Acute lumbosacral radiculopathy is most commonly due to disc herniation, although it can also be seen in degenerative spondylolisthesis. It typically presents with low back pain that radiates to the leg, often with dermatomal numbness or weakness in the leg. Lumbar radiculopathy usually affects the lower lumbar levels, and vertebral tenderness is not typical.
(Choice B) Referred visceral pain affecting the back can result from conditions such as pancreatitis and abdominal aortic dissection. However, this patient has no risk factors for these conditions, and the absence of abdominal or chest pain, nausea, or vomiting makes these diagnoses unlikely. Also, referred pain should not cause spinal tenderness on examination.
(Choice C) Patients with primary or metastatic malignancy involving bone can develop pathologic fracture following minimal trauma. However, this patient has no other features to suggest malignant pain (eg, weight loss, nocturnal pain, age >50, history of malignancy).
(Choice D) Lower back pain associated with AS flares typically begins as insidious, unilateral, intermittent pain that may progress to become bilateral and persistent. The pain is not usually sudden and severe.
Educational objective:
Patients with long-standing ankylosing spondylitis can develop bone loss due to increased osteoclast activity in the setting of chronic inflammation. In addition, spinal rigidity in these patients can increase the risk of vertebral fracture, which often results from minimal trauma.