Spondylodiscitis in ankylosing spondylitis, inflammation or trauma? A description of six cases.

An uncommon, but well recognised complication of Ankylosing Spondylitis (AS) is spondylodiscitis, a destructive discovertebral lesion also called the Andersson lesion. We describe six cases, with variable clinical presentation and radiological appearance. Two had multiple lesions, in one patient spondylodiscitis was the presenting symptom of AS. None had a history of even a minor trauma. Prognosis was good with conservative treatment including NSAID's, rest, and physiotherapy. In two cases histopathology was studied and suggested sterile inflammation as the main etiologic factor. The literature is reviewed regarding the mechanisms that may contribute to these lesions: mainly inflammatory like increasing enthesopathy or mainly mechanical like pseudoarthrosis about a fracture site. It may be that both mechanisms can result in similar destructive intervertebral disc lesions.