Chronic ankylosing spondylitis can lead to several rare long-term complications including cauda equina syndrome and inflammatory discitis especially without treatment. These complications are uncommon, but there is evidence that they can be treated with anti-tumor necrosis factor (TNF) inhibitors. We present a case of a 52-year-old male with a 30-year history of undiagnosed ankylosing spondylitis with cauda equina syndrome on initial outpatient presentation with a negative lumbosacral magnetic resonance imaging (MRI). He was admitted later that month and was found to have thoracic discitis from MRI requiring emergent decompressive laminectomy. The neurosurgeon collected a culture of the surgical site which showed rare Gram-positive cocci on Gram stain. Infectious disease was consulted, and he was started on empiric vancomycin. The culture from the surgical site did not grow any organisms. Interventional radiology (IR) aspirated the T7-T8 disk area one week later. The initial Gram stain showed rare Gram-negative rods this time, and cefepime was added to the patient's antibiotic regimen. The culture from the disk aspiration again grew no organisms. Rheumatology was then consulted and hypothesized that the patient's discitis could be secondary to inflammation from long-standing ankylosing spondylitis. The hospitalist, infectious disease specialist, and rheumatologist reviewed the case and recommended a six-week course of vancomycin and cefepime despite the negative cultures as an infectious etiology could not be excluded. He did show some clinical improvement after surgery and was started on adalimumab following completion of empiric antibiotics. This case highlights the difficulty in distinguishing between an infectious and inflammatory etiology for discitis in the setting of long-standing ankylosing spondylitis. The initiation of biological therapy without completely excluding the possibility of infection could lead to devastating consequences. It will likely be necessary to empirically treat for infection with these cases for the foreseeable future until there are more definitive tests to diagnose or exclude infectious discitis.
Keywords: ankylosing spondylitis; cauda equina syndrome; thoracic discitis.