. 2018 Sep 7;8(2 Suppl):56S–68S. doi: 10.1177/2192568217736268

Table 1.

Ankylosing Spinal Disorders (ASDs).

Group	(1) Seronegative axial spondyloarthritis (SpA)		(2) Degenerative diseases
	Definition:		Definition:
	• Genetic disposition (HLA-B27 positive)		• Primary cause unknown
	• Missing rheumatoid factors (IgG, IgM, or IgA autoantibodies); “seronegative”		• Noninflammatory

Name/Terminology	Disease	Synonym	Disease	Synonym
	Ankylosing spondylitis (AS)	Morbus Bechterew	Diffuse idiopathic skeletal hyperostosis (DISH)	Morbus Forestier, spondylosis hyperostotica, senile ankylosing hyperostosis
	Definition:		Definition:
	• Evident radiographic SI-joint changes (New York criteria¹⁴)		• Spondyloarthropathy and ossification with lateral and anterior osteophytes
	Nonradiographic axial spondyloarthritis (nr-axSpA)
	Definition:
	• Sacroiliitis visible on magnetic resonance imaging only
	• Clinical features and/or HLA-B27 detection¹⁵