This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
"Flowing wax" appearance on anterior and posterior borders of veebrae with normal interveebral disc space occuring due to ligament calcification is seen in - 
Select and explain. 
A. Ankylosing spondylitis, B. Diffuse idiopathic skeletal hyperophy, C. Psoriatic spondyloahropathy, D. RA
B: Diffuse idiopathic skeletal hyperophy
Answer: B: Diffuse idiopathic skeletal hyperophy 
Explanation: Radiological features of DISH (Diffuse Idiopathic skeletal hyperostosis) : Flowing calcification and ossification along the anterolateral aspect of veebral bodies. - Flowing wax appearance Preserved disc space. Absence of bony ankyosis of facet joints,absence of sacroiliac bony erosion,sclerosis or bony fusion.