A 62-year-old man presents to the emergency department with a 2-week history of worsening back pain and low-grade fever. He describes the pain as deep, constant, and boring, noting that it does not improve with rest or changes in position. He has a history of chronic lower back pain and intravenous drug use. On physical examination, there is exquisite point tenderness over the L3 and L4 vertebrae. Neurological examination of the lower extremities is unremarkable. Laboratory studies show a leukocyte count of 11,000/mm3 and a significantly elevated erythrocyte sedimentation rate (ESR) of 92 mm/h. Plain radiographs of the lumbar spine show subtle narrowing of the L3-L4 disc space.
Which of the following is the most likely diagnosis?
The correct answer is:
E) Vertebral osteomyelitis
The patient is presenting with the classic clinical picture of vertebral osteomyelitis, which is the most common form of hematogenous bone infection in adults. The diagnosis is strongly suggested by the presence of localized, exquisitely tender spinal processes, a constant pain that persists even at rest, and elevated inflammatory markers. In adults, the infection typically begins in the highly vascularized vertebral body and frequently spreads across the intervertebral disc to involve the adjacent vertebra. This involvement of the disc space is a key radiographic feature that helps distinguish infection from metastatic cancer, as tumors rarely cross the disc space.
Answer choice A: Ankylosing spondylitis, is incorrect. Ankylosing spondylitis is a chronic inflammatory condition that typically affects younger men. It presents with morning stiffness that improves with exercise and activity, rather than the constant, boring pain at rest and localized point tenderness seen in this patient. Furthermore, it would not typically present with an fever.
Answer choice B: Discoid lupus erythematosus, is incorrect. Discoid lupus erythematosus is primarily a cutaneous form of lupus that presents with discoid skin lesions. It does not typically involve the deep structures of the spine or present with localized vertebral point tenderness and elevated ESR in the absence of other systemic findings.
Answer choice C: Herniated nucleus pulposus, is incorrect. A herniated nucleus pulposus or "slipped disc" usually causes acute-onset radicular pain that is often relieved by specific positions or rest. It is not associated with constitutional symptoms such as fever or significantly elevated inflammatory markers.
Answer choice D: Spinal epidural abscess, is incorrect. While this is a closely related condition that often occurs concomitantly with vertebral osteomyelitis, it typically presents with rapid neurological deterioration. Findings such as focal weakness, sensory loss, or bowel/bladder dysfunction due to compression of the spinal cord or cauda equina would be expected, but this patient’s neurological examination is currently unremarkable.
Key Learning Point
Vertebral osteomyelitis should be suspected in any patient with localized spinal tenderness, fever, and an elevated ESR, especially if they have risk factors like intravenous drug use, recent dental work, or endocarditis. Staphylococcus aureus is the most common causative agent. While X-rays may be normal early on or show non-specific disc space narrowing, MRI is the gold standard for early diagnosis.
