Ankylosing sponylitis (AS; also known as Bechterew's disease; Bechterew syndrome; Marie Strümpell disease / Marie Struempell disease / Spondyloarthritis) is a chronic, painful, degenerative inflammatory arthritis primarily affecting spine and sacroiliac joints, causing eventual fusion of the spine; it is a member of the group of the autoimmune spondyloarthropathies with a probable genetic predisposition. Complete fusion results in a complete rigidity of the spine, a condition known as bamboo spine.