Basing on roentgenological observation of the course of the disease, and on postmortem examination, of a patient with polysegmental Andersson lesions (known as spondylodiscitis) in ankylosing spondylitis, the article reports on the histological and often also clinico-roentgenological possibility of differentiating between an inflammatory and non-inflammatory type of this destructive lesion. The non-inflammatory type of Andersson lesion reflects a fracture due to fatigue, or its sequel, eg pseudarthrosis, in the stiffened axial skeleton. In this particular patient, renal osteopathy had favoured the genesis of the disease.